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These results suggest that MGL-Tg mice show similar levels of social interaction and social interest as WT mice, regardless of the familiarity or the reciprocity of the social stimulus. Therefore, in contrast to high-fat food, the impaired CPP of MGL-Tg mice to social interactions may represent a problem of consolidation rather than reward processing.It has been postulated that drugs of abuse ‘hijack’ natural reward circuits . We therefore tested MGL-Tg mice in cocaine CPP to see if the drug might recruit 2-AG signaling. In a standard CPP box, we conditioned mice to either saline or cocaine in four 30-min sessions, alternating over a total of 8 days . Both WT and MGL-Tg mice developed a strong post-conditioning preference for the cocaine chamber . This result suggests that the conditioned effects of cocaine do not depend on 2-AG signaling. Furthermore, it indicates that MGL-Tg mice are cognitively able to perform CPP in general.In particular, we have recently shown that social contact increases anandamide mobilization in the NAc, and that this response plays an important role in social reward . If 2-AG is also involved in social-reward processes, as our previous results suggest, social stimulation should increase 2-AG levels. We isolated juvenile C57Bl6J mice for 24 h, and then returned half to their cage-mates while keeping the other half isolated for 6 h . We collected and snap-froze their brains, took micro-punches of tissue, and measured lipid content using liquid chromatography-mass spectrometry . We found that, compared to mice that remained isolated, socially stimulated mice showed an 83% increase in 2-AG levels in the nucleus accumbens and a 40% increase in the ventral hippocampus , cannabis vertical farming but did not show a change in 2-AG levels in the medial prefrontal cortex . This suggests that social interactions cause amobilization of 2-AG signaling.

Levels of the endocannabinoid anandamide, in contrast, were unchanged in the NAc after this 6-h social stimulation . It is important to note, however, that we previously observed an opposite pattern for a 3-h social stimulation, which elicited an increase in levels of anandamide but not 2-AG . It is possible that social contact elevates 2-AG levels due to an increase in general activity. Therefore, we compared 24-h-isolated animals to control animals that were similarly handled but remained social . In this comparison, isolation had no effect on levels of 2-AG in the NAc, but decreased 2-AG by 55% in the vHC and by 50% in the mPFC . This profile of 2-AG change was not the opposite of that elicited by social stimulation – that is, NAc 2-AG increased during stimulation but did not change during isolation, and mPFC did not change during stimulation but decreased during isolation. In contrast, the pattern of 2-AG levels was opposite in the vHC – 2-AG increased during stimulation and decreased during isolation. The magnitudes of these opposing effects in the vHC were relatively comparable . Isolation also did not alter levels of anandamide in the NAc . We interpret these results to mean that social stimulation induces 2-AG signaling in the NAc that is distinct from what is active during baseline social activity, i.e. a ‘social 2-AG tone.’ Other contributions in the mPFC and vHC remain to be determined. Nevertheless, because the NAc is a key region for brain reward, the results suggest that 2-AG likely contributes to the reward of social interactions. These results support the previous finding that MGL-Tg are deficient in social CPP.It has been postulated that the signaling system underlying reward for social interactions overlaps with those involved in the control of other natural rewards .

The available literature emphasizes the important role of the endocannabinoid system in motivated behaviors , raising the theoretical possibility of an endocannabinoid substrate that is common to different natural rewards. Our study provides evidence in support of this possibility through complementary behavioral analysis of a unique model of selective 2-AG reduction with biochemical analysis of 2-AG mobilization in brains regions important for reward. Our main findings are that 2-AG reduction impairs CPP for social interactions, and that social stimulation increases 2-AG levels in the NAc. These results clearly identify 2-AG as a reward signal for social interaction. Additionally, we found that 2-AG reduction impairs CPP to high-fat food. Collectively, our results suggest that 2-AG is involved in regulating the incentive salience of two essential aspects of behavior, feeding and social contact. A limited number of studies have addressed the involvement of endocannabinoid signaling in the control of social behavior. Genetic CB1 deletion and administration of CB1 agonists alter social interactions. The effect of CB1 agonists can be bidirectional, depending on dosage and thus likely the competing circuits involved . Furthermore, increasing anandamide activity via genetic deletion or inhibition of its hydrolytic enzyme, FAAH, increases direct social interactions in mice and social play in rats . Recently, we demonstrated that anandamide-mediated endocannabinoid signaling is important in the control of social reward . Social contact mobilizes anandamide in an oxytocin receptor-dependent manner. Consistently, chemogenetic activation of oxytocin neurons in the hypothalamus increases anandamide mobilization in the NAc. Pharmacological and genetic enhancement of anandamide activity increases social CPP and offsets the effects of oxytocin blockade.

These results suggest that a cooperative oxytocin-driven anandamide signal regulates social reward . Thus, the distinct effects of CB1 agonists and FAAH inhibitors on social behavior present a complex picture with two knowledge gaps: whether 2-AG-mediated activation of CB1 receptors also participates in social behaviors and if so, the type of interaction and associated neural circuits that are regulated. The present study addresses these gaps by exploiting a new transgenic mouse to reduce endogenous 2-AG signaling without overt compensation, using CPP to specifically model social reward rather than interaction in general, and measuring socially mobilized 2-AG levels in brain areas that are part of the reward circuit. At the same time, our study raises an important question for future studies. The temporal profiles of socially stimulated 2-AG versus anandamide are distinct. In the NAc, a 3-h social stimulation increases the levels of anandamide, but not 2-AG , whereas a 6-h stimulation elevates levels of 2-AG, but not anandamide . Distinct temporal profiles of endocannabinoid mobilization have been demonstrated in other situations – for example, in response to drugs of abuse as well as in stress-induced analgesia mediated by the periaqueductal grey – and thus are likely to be functionally meaningful. One plausible explanation is that anandamide is involved in the initial saliency of a social encounter whereas 2-AG is involved in consolidating information from prolonged social contact. This hypothesis is supported by two pieces of evidence. First, oxytocin is thought of as a saliency signal that is more proximal to the initial processing of social sensory information . Oxytocin tightly drives anandamide formation in the NAc, whereas 2-AG production is driven by prolonged social contact but not oxytocin . Secondly, anandamide is more specific to social reward whereas 2-AG is more generalizable to other rewards, as elevating anandamide increases CPP for social interactions but not for high-fat food or cocaine , whereas reducing 2-AG activity reduces CPP to both social interactions and high-fat food . An extensive literature also supports an important role of CB1 signaling in food reward. CB1 receptor antagonism and genetic deletion suppress not only food intake, but also CPP and self-administration . In contrast, information is sparse regarding the individual endocannabinoid transmitters that might be involved. Available studies have found that systemic administration of exogenous anandamide increases food intake , and 2-AG administration into the NAc increases feeding . Exogenous administration, however, does not simulate physiological conditions. The intake phenotype may also equivocate the metabolic and motivational aspects of endocannabinoid signaling. Our study addresses these concerns by specifically manipulating 2-AG signaling and using a model of CPP to represent the rewarding value of high-fat food. A lack of CPP encompasses different impairments in aspects of reward signaling, such as the processing of initial sensory cues, integration and recruitment of limbic regions, and the consolidation of the memory for the reward. In order to specify the component in which 2-AG may play a larger role, cannabis drying rack we also measured the intake of high-fat food and the social interactions of MGL-Tg mice. We found that MGL-Tg mice show less intake of high-fat food but appear normal in direct, reciprocal social interactions as well as social approach. In light of the lack of CPP for both high-fat and social stimuli in MGL-Tg mice, these results may point to a dichotomous role for 2-AG – perhaps in the processing of high-fat reward versus the consolidation of social reward. These speculations are consistent with the aforementioned feeding literature and prolonged action of 2-AG, as compared to anandamide, after social stimulation. In line with this thinking, the phenotype of a lack of CPP across high-fat and social stimuli, but present CPP for cocaine, must be taken to represent a qualitative rather than quantitative difference. That is, reducing 2-AG impairs different processes for the reward signaling of these stimuli, rather than different amounts of the same process. Perhaps because cocaine bypasses 2-AG-regulated signaling and is more dopamine-dependent, CPP develops regardless of 2-AG signaling.

Nevertheless, whether 2-AG influences dopamine in MGL-Tg mice and whether dopamine is the ultimate effector of all these rewards remains to be determined. Indeed, the magnitude of cocaine CPP as a function of dosage does not vary in a graded manner, but develops in an all-or-none fashion, starting at the minimum dose range that we used . Additional investigation into these possibilities is needed. While MGL-Tg mice represent a technological advance to address the aforementioned knowledge gaps, phenotypic results also come with potential weaknesses. First, forebrain 2-AG reduction may alter general cognition so that mice are unable to perform the CPP task. However, our finding that MGL-Tg mice develop normal cocaine CPP argues against this possibility. Second, improper development or socialization may render MGL-Tg abnormal. But this is unlikely because MGL over expression is controlled by the CAMKII promoter, which lacks developmental activity, and MGL-Tg mice do not show overt abnormalities in tests of general health . Normal levels of social interaction and social approach also speak to proper socialization. It remains true that our results do not completely exclude these possibilities. More nuanced forms of cognition or social interaction may not be detected in our tests. In conclusion, our study identifies a common endocannabinoid substrate – 2-AG – in the regulation of two natural rewards, feeding and social contact. This identification provides a basis to motivate further investigation of the circuitry and physiology regulated by 2-AG signaling in natural reward, the dichotomous roles of anandamide and 2-AG in different social contexts, as well as how such signaling may be exploited in addiction.A core feature across autism spectrum disorder is impairment in social functioning. People with ASD restrict themselves to repetitive behaviors and show deficits in social reciprocity and communication1 . The underlying basis for social impairment in ASD is unknown and no pharmacological treatment is available. One theory – the social motivation theory – posits that the psychopathology of ASD is rooted in a decreased desire to be social3. The neural substrates of normal social behavior are only now beginning to emerge . Perhaps the best account so far has come from the study of oxytocin. This neuropeptide is crucial in many aspects of social behavior, including affiliation and reward. Investigations are ongoing into the contributions of the oxytocin system to ASD and oxytocin-based therapies for ASD8 . Recent reports suggest that early treatment with oxytocin may be useful for improving social behavior in animal models as well as in human patients10. Nevertheless, identifying the key neural systems underlying social behavior and understanding how they interact with oxytocin remains an enormous challenge5 . One candidate is the endogenous cannabinoid system, a modulatory neurotransmitter system that may play an important role in social behavior. This signaling complex consists of lipid-derived messengers called ‘endocannabinoids’ whose actions in the brain are mainly, albeit not exclusively, mediated through CB1 cannabinoid receptors. A series of enzymes catalyze endocannabinoid synthesis and degradation to control the activity of these substances. Fatty acid amide hydrolase catalyzes the intracellular hydrolysis of the endocannabinoid anandamide. In an effort aimed at probing anandamide function in social behavior, we found that genetic removal of FAAH in mice increases direct social interactions, while Trezza et al. noted that pharmacological FAAH inhibition promotes social play in juvenilerats. More recently, we identified a signaling mechanism by which oxytocin drives anandamide mediated signaling at CB1 receptors to control the rewarding properties of social interactions.

Similar to Fig. 3, without the analyzer, we can see clearly two horizontally shifted LCP and RCP images, as shown in Fig. 4 I– L. The separation between two images determines how sharp the edge can be resolved, which is also confirmed by the final edgedetection images shown in Fig. 4 M–P. The highest resolution achieved is around 2 μm , close to the diffraction limit of the optical system, by using a meta surface with Λ of 8,000 μm. It is worth to note here that these results are taken under the condition of a planar object at the focal plane. Therefore, for thick 3D object, multiple measurements need to be taken by scanning the focal plane over the objects and combine each focal plane result together. In the case of the samples with circular birefringence inclusions, the LCP and RCP components will gain different phases, so that the combined LP components in the overlapped area may not be completely canceled out after the second linear polarizer. Although this indicates the contrast between the edge and the background will be compromised, additional circular birefringence information can be revealed.Social behavior is a human hallmark. People spend an enormous amount of time engaging in social interactions. They form loose relationships with acquaintances or strong relationships with friends and family members. Together, these connections form social networks that range from schools and companies to ethnic identities and nationalities. The social nature of humans has been recognized since Aristotle . Its crucial role in human life has been studied in a spectrum of fields in the social sciences. Only recently, however, have biological approaches been used to study the underlying physiology of social behavior. These approaches have contributed to understanding the neural signaling that may regulate social behavior as well as the impact of social factors on mental and physical health. These lines of research have given rise to the aggregated field of social neuroscience . Firstly, this field has emphasized the importance of social relationships.

Social contact is essential for the health of the brain and the body . For example, social isolation in critical periods of life wreaks havoc on cognition, vertical racking system emotion and immune responses. Second, social support is a crucial factor for neuropsychiatric and bodily diseases, both in susceptibility and recovery . Examples abound: abnormal social development predicts addictive behaviors and conduct disorder; social support buffers against not only mental illnesses such as depression but also physical ailments such as chronic pain and recovery from myocardial infarction. The multitude of health problems associated with social factors also highlights the complexities and fragilities involved in a growing person navigating the social sphere. The nature of social relationships changes significantly over a lifespan, requiring the development of unique social skills. For instance, a child must transition from a strong maternal attachment to mostly peer contact over the course of adolescence, the young adult must transition from single hood to a state of attachment with a significant other, while the elderly must take on new roles imposed by accrued experience and reduced physical strength. These distinct types of experiences involve a range of cognitive and emotional processes that undoubtedly impact brain development. The impact is likely mutual, as proper development is crucial for ongoing social function. Such mutual interactions must be finely tuned. To date, the neural processes underlying these transitions and the neural systems that regulate social behavior are largely unknown. Perhaps the best biological account so far has been the study of oxytocin. Oxytocin is a peptide, comprised of nine amino acids, that has long been known for its peripheral hormonal effects in parturition and lactation . More recently, research has elucidated its central effects in affiliative behaviors and social reward. Tom Insel, Larry Young, and colleagues performed seminal studies in prairie voles . They compared these rodents, which display monogamous pair bonding, to the genetically similar but polygamous montane voles , and found distinct differences in their oxytocin systems .

One key difference is that compared to montane voles, prairie voles have increased oxytocin receptors in the nucleus accumbens, a brain region important for reward signaling. In a series of pharmacological and genetic studies, these authors elaborated the crucial roles of oxytocin in social memory and pair-bond formation. Since then, work on oxytocin remains an active area of ongoing investigation. Modern neuroscience tools have been used to examine the circuit dynamics of oxytocin signaling. For example: oxytocin neurons of the paraventricular nucleus of the hypothalamus project to the amygdala to modulate evoked fear ; oxytocin neurons coordinate with serotonergic neurons from the dorsal raphe nucleus tocontrol peer social reward ; oxytocin in the hippocampus controls signal-tonoise ratio for information processing ; oxytocin receptors are left-lateralized in the auditory cortex to enable maternal retrieval of separated pups . Human studies have been hampered by the difficulty in delivering oxytocin to the brain, but this obstacle was partly removed by the recent development of an intranasal oxytocin spray. Although the pharmacokinetics of intranasal oxytocin is still unclear, its central effects have been widely documented in numerous high-profile publications. For example, intranasal oxytocin impacts one’s trust of others . Intranasal oxytocin is also being tested in ongoing trials for indications including anxiety, autism spectrum disorder, and drug addiction. Drug development is still at an early stage , but a first a sign of success on sociability in autism-spectrum patients was reported .More recent studies of marijuana use in humans are also in line with the assumption that this drug may affect social behavior. In a survey of students who were experienced marijuana users, more than 70 percent said that intoxication makes them want to interact more with others, because the group takes on ‘a much greater sense of unity, or real social relationship’ . More than 80 percent reported that they felt more insightful and empathetic of others but they are also less able to play social games, which suggests that marijuana makes users more intuitive and social but hinders their social skills .

Worth noting, however, is that, a substantial portion of experienced users also preferred to ingest the drug in isolation, perhaps because they like to feel ‘isolated from things around me’ . This contrasts with more casual users who typically ingest the drug in a social setting. Experimental studies have also found that marijuana alters social behavior. In a study of aggression, two groups were given a shared task with a frustration stimulus. Compared to placebo, the group given marijuana provided self-rated reports of higher cooperativity and decreased hostility . Interestingly, the authors also note that marijuana may have been disinhibitory, such that the users were more willing to express their feelings. Similarly, an experimental study in a small group setting found that active marijuana changed the distribution of social activities by decreasing time spent in verbal exchanges while increasing time spent in co-actation, i.e. engaging in a shared activity, such as playing a game . Together, these studies indicate that active marijuana use can exert powerful effects on social interactions. They also imply that the effects likely depend on the dose, stressful stimuli, and the past experience of the user. Interestingly, the studies note differential effects on the emotional aspects of social experiences versus the skills needed for social interaction . Thus, the neurobiological consequences of marijuana likely involve a range of dissociable effects throughout the engagement and ongoing development of social interactions.The endocannabinoid system, a modulatory neurotransmitter system in the brain, mediates the effects of the psychoactive principle in marijuana, Δ9 -tetrahydrocannabinol. Work on the endocannabinoid system in social behavior remains limited and has emerged more recently. Meanwhile, indoor grow facility the more established roles of this system in anxiety, reward, pain, and cognition have hinted at overlapping functions in social behavior. The endocannabinoid system consists of lipid-derived messengers called ‘endocannabinoids’ whose actions in the brain are mainly, albeit not exclusively, mediated through CB1 cannabinoid receptors. A series of enzymes catalyze the biochemical synthesis and degradation of endocannabinoids to control their signaling activity . These cascades typically start with the release of particular lipid species from phospholipid membranes, involve multiple biochemical pathways, and end with recycling or the directing of products to alternative biochemical signaling cascades. The canonical route for the synthesis ofanandamide is thought to involve a calcium-dependent phospholipase D that releases anandamide by hydrolysis of the phospholipid precursor N-arachidonoylphosphatidylethanolamine . Whether and how other enzymes may be involved is unknown, making the molecular mechanisms and localization of anandamide signaling unclear. Anandamide is mainly degraded via intracellular hydrolysis by the enzyme fatty acid amide hydrolase . On the other hand, the mechanisms of synthesis for the other endocannabinoid 2-arachidonoyl-sn-glycerol are clearer. 2-AG is generated via the hydrolysis of the intracellular second messenger 1,2-diacylglycerol, by diacylglycerol lipase-α . DGL-α can be coupled to different receptors upstream for the activation of 2-AG by different signaling systems. For example, in glutamatergic neurons, DGL-α forms a complex with the type-1 metabotropic glutamate receptor, mGluR5, which is scaffolded by proteins such as Homer-1a .

The efficiency of coupling in this complex represents a molecular mechanism for signaling regulation. 2-AG is mainly degraded by the serine hydrolase monoacylglycerol lipase . Both anandamide and 2-AG are unconventional in the sense that they act in a retrograde manner to suppress presynaptic firing . In this regard, they can be thought of as ‘synaptic circuit breakers’ to curb incoming depolarization . In line with this idea, 2-AG, for example, is generated upon glutamate spillover to the ‘perisynaptic’ region rather than within the post-synaptic density proper – an anatomical feature that allows homeostatic negative feedback. This is not to say, however, that this type of synaptic feedback is the only mode of endocannabinoid signaling. Another unique property of the system is that endocannabinoids can also act as diffuse localmessengers. Anandamide possesses properties of a volume transmitter – diffusing and affecting multiple neighboring cells – whereas 2-AG is thought of more as a point-to-point synaptic transmitter. Accordingly, a third property is that, when the messengers work in concert, their temporal profiles may differ during signaling. For example, when an animal is subjected to acute stress, 2-AG increases within minutes in the periaqueductal grey whereas anandamide rises in the course of an hour to mediate stress-induced analgesia . In other situations, the directionality of changes in 2-AG and anandamide may actually be opposing. For example, non-contingent alcohol exposure increases extracellular 2-AG levels in the nucleus accumbens , but reduces anandamide . In the brain, 2-AG is almost 1000-fold more abundant than anandamide. Although this difference could in part be accounted for by structural, intermediary, or otherwise signaling-incompetent pools of 2-AG, the substantial difference nevertheless suggests dichotomous patterns for signaling action. A fourth unique property is that, as lipid mediators, the endocannabinoids are not stored in traditional vesicles but instead ‘demobilized’ in phospholipid membranes at baseline; they become ‘mobilized’ during signaling activity as they are synthesized ‘on-demand’. This means that molecular mechanisms for their recruitment must involve synthetic enzymes for mobilization. This necessity has implications for understanding interactions between systems, from the circuit down to the molecular level. If the synthetic machinery for anandamide is less well known, for example, it becomes difficult to dissect the molecular interactions needed for its recruitment. This can be seen in the contrast between several well-documented cases of 2-AG recruitment by various G-protein-coupled receptors versus only one for anandamide. G-protein-coupled receptors that recruit 2-AG include type-1metabotropic glutamate receptors , type 1/3 muscarinic acetylcholine receptors , and type-1 orexin receptors . D2 receptors in the dorsal striatum have been shown to recruit anandamide .The brain distribution of components of the endocannabinoid system is consistent with a role in social behavior. CB1 receptors are highly expressed in associational cortical regions of the frontal lobe and subcortical structures that underpin human social-emotional functioning . For example, the behavioral variant of frontotemporal dementia, characterized by indifference to social conflict and eccentric social conduct, involves neurodegeneration of regions in salience networks, including the anterior cingulate cortex, frontoinsular cortex, prefrontal cortex, striatum, and thalamus .

Our survey respondents, because of their large holdings, may be unusually exposed to cannabis growers physically because their larger properties may have more contact with cannabis growers. At the same time, these respondents might be better able to survive economically in a Humboldt County without cannabis. It is unclear if the experiences and perspectives of many Humboldt County smaller landowners would be similar to those of these large landowners. For many in Humboldt County, the impacts of cannabis production on property and the environment are a central concern. Respondents mentioned problems involving shared roads and fences, illegal garbage dumping and contamination, deforestation, fire hazards, feral dogs and impacts on wildlife and domestic livestock. One respondent wrote that “Growers leave a mess, steal water, tear up roads, let guard dogs damage neighbors’ property, including livestock, poison wildlife, increase soil erosion and threaten people.” In many ways, it seems that land ethics are at the center of the concerns that traditional agricultural producers harbor about the new wave of cannabis growers. Though respondents remarked on cannabis growing’s direct impacts on the environment, they also largely agreed that the cannabis industry is causing fewer young people to enter traditional farming careers — and that growers are taking over working lands. It is unknown if the rates at which successive generations stay in the family business are lower in Humboldt County than in rural communities less influenced by cannabis. For families who have managed and lived off these lands for decades — most of them for more than 50 years — these shifting stewardship ethics threaten their immediate environment as well as their very identity.

One of the more controversial questions in drug policy today is whether the trend toward legalizing marijuana for medicinal and adult recreational use could increase illicit marijuana use among young people . Since 1996, 28 U.S. states and the District of Columbia have legalized the production and sale of marijuana for medicinal use , clone rack and eight have legalized marijuana for adult recreational use. Medical marijuana laws could potentially increase the availability of marijuana and reduce perceptions of its harmfulness, leading more young people to try it. State medical marijuana laws include regulations that protect young people from illegally obtaining marijuana . But if these restrictions are not carefully enforced, young people could gain increased access to marijuana through the diversion of medical marijuana into illegal markets, which could also lower its price . Marijuana use by young people is associated with lasting detrimental changes in cognitive functioning of the developing brain, and poor educational and occupational outcomes . Use increases the risk of unintentional injuries and auto fatalities, mood and psychotic disorders, and drug dependence, especially when use is initiated at a young age . Long term marijuana smokers have a disproportionate burden of upper respiratory illnesses, including chronic bronchitis and some cancers, and an increased risk of cardiovascular disease . Medical marijuana producers and retailers are promoting new, more potent products such as oils often used as inhalants with tetrahydrocannabinol concentrations ranging from 40 to 70 percent . They are also developing new products that appeal to youth, such as packaged edibles and candies, that may increase the hazard of overdose due to their relatively slow rates of absorption and perceived intoxication .

These products could increase the risk of overdose in young people, who tend to be less experienced users with low tolerance levels. Studies have reported little evidence that medical marijuana laws increase marijuana use among young people , although well controlled studies consistently report increased consumption in adults . Using the Youth Risk Behavior Survey, researchers have compared high school students’ consumption before and after medical marijuana laws were enacted, finding no evidence of rising consumption on a national basis . A national study of 12–17 year old found that medical marijuana laws had no causal impact on consumption , as did a carefully controlled national study of 13–18 year olds . Wen et al. reported a five percent increase in the likelihood of trying marijuana among 12–20 year olds who dwell in states with medical marijuana laws, but the study was limited by the need to pool such a broad range of ages. Prior studies have ignored or been unable to detect age related variation in the impact of medical marijuana laws by pooling children aged 12–17, or even 12–24, or by studying particular age groups in isolation. Age-related variation is important to capture because young peoples’ access to marijuana and their developmental susceptibility to drug related harms differs by age . Most studies have focused on high school students who are likely to have greater access to marijuana and are more susceptible to social pressures than early adolescents . Meanwhile, young adults different substantially from these younger groups, both in terms of development and access to drugs, being in the peak years of engagement with psychoactive substances during the lifespan .

We performed multi-level, serial cross-sectional analyses on 10 annual waves of the U.S. National Survey on Drug Use and Health , from 2004 to 2013. Unlike many prior studies, ours included the key years of 2010–2013—a period of rapid acceleration in the number of states implementing medical marijuana laws , but before state recreational marijuana laws began implementation. In addition, our analyses compared young people across developmentally distinct age groups to account for important age-related heterogeneity in access to marijuana, in the propensity to experiment with psychoactive substances, and in the potential harms of marijuana use.We examined three dichotomous outcomes at the individual level: self-reports of the accessibility of marijuana, consumption of marijuana within the past month, and initiation or first-time use of marijuana during the past year. The NSDUH framing of the marijuana questions references smoking, edibles, and oils. Individual-level, age-appropriate predictors from the NSDUH dataset were included in the analysis. Across all three age groups, these included sex, race/ethnicity, family income, poor or fair health, and living in an urban area. We included an indicator of poor or fair health status to control for the possibility that participants in medical marijuana states might engage in the legal use of marijuana for health reasons. For early and late adolescents, we also controlled for parental monitoring and participation in group fights, variables that could be indicators of the protective factor of parental involvement and the risk factor of delinquent behavior, respectively. For young adults, additional controls included employment, college attendance, parental status, and marital status. These are strong protective factors mitigating against drug use in this age group . We augmented the NSDUH data with annually updated state-level data on medical marijuana laws and other relevant control variables. For state-level controls, we drew on publicly available sources such as Polidata , including per capita drug courts and whether or not marijuana possession had been decriminalized. We considered a wider range of state-level controls representing demographic, political and religious factors, and aspects of state drug control policies. For the sake of parsimony, we included controls that were most associated with outcome variables. Data collection on state medical marijuana laws included gathering all state statutes and subsequent regulations, 4×8 tray grow and validating information against publicly available data sources and through telephone calls with state officials. Throughout the study, we conducted regular updates to monitor changes in regulations and amendments to state laws . Analyses incorporated a dichotomous measure reflecting whether a state did or did not have a medical marijuana law enacted during any given year of observation. Thus, a law passed or enacted at any point in a calendar year would count that state as a medical marijuana state for that year’s analysis. We also examined a wide range of characteristics of state laws, such as the amounts of marijuana legally allowed for possession and home cultivation, medical conditions covered, and the number of dispensaries in each state. Through a systematic measurement process, we created and validated a scale capturing the capacity of a given medical marijuana law to control marijuana distribution and diversion into illegal markets .We concatenated 10 annual waves of the NSDUH and all state-level indicators into a single data file. We conducted all analyses using Stata version 13 . For descriptive analyses of each survey year, we used weights to adjust for sampling design effects and non-response ; similar weights were not available for multi-year analyses. Following Williams and others , we accounted for shared variance among participants within states by calculating standard errors clustered at the state level in our regression models.

Our analytic approach used logistic regression to predict marijuana consumption and initiation at the individual level separately for early adolescents, late adolescents, and young adults. A key analytic concern is that people in states that pass medical marijuana laws hold more permissive views about the drug . These more positive perceptions about marijuana may drive both the passage of the medical marijuana laws and higher rates of consumption . We incorporated that possibility into our uncontrolled comparisons of young people who dwell in states with medical marijuana laws compared to those who do not . By controlling for state-level fixed effects , we were able to examine whether medical marijuana laws have distinct causal impacts on marijuana consumption and initiation . The coefficients for each state controlled for any state-specific confounding not already captured by other control variables in the models. This technique allowed us to rule out the possibility that unobserved state-level confounders account for any associations found between state medical marijuana laws and young people’s consumption and initiation of use.Using the most recent NSDUH survey, 2013, we compared rates of access to marijuana, past-month marijuana use and past-year initiation across early and late adolescent youth and young adults. Table 1 shows pronounced differences in the populations of young people living in states with medical marijuana laws compared with those who were not. These demographic differences—especially ones associated with drug-related attitudes—underscore the importance of applying individual-level controls in the analysis. For example, in 2013, individuals living in medical marijuana states were disproportionately white and Hispanic. Young adults living in medical marijuana states were comparatively less likely to be married and to have children. Figure 1 shows a positive age gradient in rates of reporting that marijuana is easily accessible and in past-month marijuana use: The highest prevalence occurred among young adults at 19.1%, then 11.9% of late adolescents and 2.2% of early adolescents . In contrast, initiation of marijuana use in the past year was most common among late adolescents , with young adults the next most likely to initiate marijuana use and early adolescents the least likely to have tried marijuana for the first time in the past year .Table 2 shows logistic regression models predicting past month marijuana consumption that include all individual and state-level controls, and annual and state-level fixed effects. Results provided no evidence of a causal relationship between living in a state where medical marijuana was legal and the past month use of marijuana. Across all age groups, the odds ratio associated with medical marijuana state residence was not statistically significant. Table 3 provides similar fully controlled results for logistic regression analyses predicting past-year initiation of marijuana use. Results show that young adults dwelling in states that have legalized medical marijuana are significantly more likely to initiate marijuana use than counterparts in non-medical marijuana states . Such a relationship is not evident for early or late adolescents . We performed additional analyses to rule out several alternate explanations of these findings. Incorporating the amount of time since the passage of the medical marijuana law into our models produced similar results regardless of duration of the law. To rule out the possibility that young adults are more likely to initiate marijuana use due to mental health conditions, which in some states are legally allowed indications for a medical marijuana prescription, we estimated an alternate version of the models that included additional mental health-related variables, specifically, past-year use of mental health treatment and past-year unmet need for mental health treatment. After introduction of these additional controls, the effect of living in medical marijuana state remained statistically significant for young adults . We also considered the possibility that states with less restrictive medical marijuana laws could have more significant impacts on young people.

We examined data from an on-going longitudinal natural experiment , which has followed a cohort of mostly Latinx students starting at the beginning of 9th grade through age 23 currently. Racial/ethnic and socioeconomic disparities exist in youth outcomes and comparative studies suggest that ethnicity may influence perception of school climate. Furthermore, within the Latinx experience there exists a diversity of national and indigenous heritages, degrees of acculturation and integration, and immigration stories. While ethnicity was not the focus of this analysis, we believe study of this predominantly Latinx population makes a valuable contribution to the extant literature. Additionally, RISE-UP examined a range of school climate characteristics, including school safety and order, student-teacher relationships and support, and disciplinary style. We examined a variety of different adolescent behaviors , and academic outcomes , so as to permit a more holistic analysis that incorporates health and behavior with cognitive development.This is a secondary analysis of data from the RISE-UP study, a longitudinal natural experiment designed to assess the effects of high-performing high schools on health behaviors among low-income, minority adolescents in Los Angeles. Five high-performing charter high schools were selected based on: enrollment of predominantly economically disadvantaged students , academic performance in the top tertile of public schools in Los Angeles County based on 2012 Academic Performance Index derived from standardized test scores, and use of an admissions lottery. Eighth grade students who were applying for 9th grade admission into high school were randomly sampled from the admissions lottery list of “winners” and “losers” during two consecutive years in the spring before entry into high school . To be eligible, plants rack students had to speak English or Spanish fluently and reside in Los Angeles County. Of 1509 eligible students, 1270 were enrolled and consented to participate in the study .

Further details of the original study are published elsewhere. 11 The institutional review board of the RAND Corporation and the University of California Los Angeles approved this study. Written parental consent and student assent were obtained from all participants.Participants completed a baseline, face-to-face, computer-assisted survey from March of 8th grade through November of 9th . Similar follow-up surveys were conducted in the spring semester of 10th grade and 11th grade . Interviews were conducted in the patient’s primary language with the aid of bilingual research assistants and in a sufficiently private location of the participant’s choice. A computer-assisted self-interview was used to minimize social desirability bias for potentially sensitive topics related to substance use and sexual and delinquent behaviors. A total of 1159 students completed the survey in 10th grade and 1114 students completed the survey in 11th grade for an 87.8% retention rate through 11th grade.At each survey, students reported their frequency of alcohol and cannabis use in the last 30 days, dichotomized . Students also completed an alcohol misuse scale and a cannabis misuse scale , which assessed high risk substance use behaviors and its negative consequences . Scale items were dichotomized and summed to produce a total score with higher scores representing greater misuse characteristics. Students reported on delinquent behaviors that are associated with negative life outcomes using the delinquent behavior index from the National Longitudinal Study of Adolescent to Adult Health and included: painting graffiti, damaging someone else’s property, shoplifting or stealing, running away from home, driving a car without the owner’s permission, burglary, armed robbery, selling illicit drugs, participation in a gang in the last year, and having ever participated in a gang fight. The score was dichotomized . Students were asked if they carried a weapon such as a real gun or knife in the last 30 days and if they had been in a physical fight in the last 12 months. These questions were combined into one dichotomous variable of any of the two behaviors .

Students responded to several questions about high-risk sex behaviors including not using contraception, ever becoming pregnant, and having multiple sexual partners . Students also answered two questions about bullying at school in the last 12 months, which were dichotomized: 1)whether someone had bullied or picked on them and 2) whether they themselves had bullied or picked on someone . We also collected information on several academic outcomes. For truancy, students reported if they had cut or skipped classes in the last 12 months, dichotomized . Students also responded whether they transferred to another school for any reason in the last academic year, dichotomized . We obtained student grade point average from official school transcript records . We used self-reported GPA when we could not obtain school transcripts . We obtained standardized test scores for each student for 8th grade and 11th grade from the California Department of Education. Math and English proficiency were determined by the California Standardized Testing and Reporting Program and the California Assessment of Student Performance and Progress . We compared those who failed to meet 11th grade standard versus those who were proficient or above. We obtained data on college matriculation into a 4-year college from the National Student Clearinghouse, a nonprofit organization providing enrollment and degree-verification services to colleges and universities. These data were obtained on 10/30/2019 corresponding to about 1.5-2.5 years after the end of 12th grade.In the 10th and 11th grade surveys, students were asked about several aspects of their school environment. These school climate measures are not comprehensive but chosen to represent a diversity of school climate domains. School order refers to the amount of confusion and chaos in the classroom34 and was assessed using a scale based on the Confusion, Hubbub, and Order Scale developed by Matheny and colleagues.

We analyzed the measure as school order, the inverse of school chaos, so that higher scores indicated a more positive schoolclimate . School safety was assessed using the Chicago Consortium on School Research Student Perceptions of Safety Scale, a 4-item measure of self reported safety in and around school . Using a modified questionnaire from the annual survey of Chicago public schools students reported perceptions of teacher-student relationships on a four point scale from strongly disagree to strongly agree. We simply summated the responses to three questions into a single variable representing perceived teacher respect for students . We combined three additional questions into a second variable representing teacher support for college . School disciplinary style was assessed according to student ratings of school support and structure as previously described. These two rating scales were categorized into tertiles, and then combined to create a single perceived school disciplinary style variable with five categories: authoritative , authoritarian , permissive , neglectful , and average .We conducted linear and logistic regression analyses to examine the relationship between each school climate variable and each adolescent health, behavioral, and academic outcome separately. For these analyses, the continuous school climate variables were standardized so that a 1-point change in each scale equaled one standard deviation. All models were adjusted for student gender, Latinx ethnicity, USA birthplace, native English language, parental birthplace, plant growing trays parental employment, parental education and parenting style. In each model, we also controlled for the outcome measures at baseline . For models examining GPA and standardized test scores, we controlled for these outcomes from middle school. All models used generalized estimating equations with a random effect for school to adjust for clustering of outcomes at the school-level. The analyses were restricted to the sample of respondents who completed baseline, 10th grade and 11th grade surveys. Among this analytic sample, values were missing for 2.3% or less of the sample for any single measure. 5.1% of the sample were missing data for the 8th grade standardized test scores, 11.7% were missing 11th grade standardized test scores, 2.3% were missing transcript and self-reported GPA from middle school, and 0.3% were missing transcript and self reported GPA from high school. Missing values were multiply imputed using 100 replicates so as to maximize the use of available data across a large number of variables. Sensitivity analyses using list wise deletion produced similar results. STATA 14.0 was used for all analyses. The original RISE-Up sample was comprised of 1270 students at baseline , 91% of whom completed the 10th grade survey. This study was limited to the 1114 students who completed the baseline through 11th grade surveys. Table 1 summarizes student and parental demographic characteristics. Just under half of the sample were males , 90% were Latinx, 87% were born in the USA, and 40% were native English speakers. One-quarter of students reported having at least one parent born in the USA, 89% had one or more parent working full-time, and 52% had one or more parents graduate from high school. Compared to those in the analytic sample, subjects who were lost to follow up before the 11th grade survey were more likely to be male , white , native English speaker , and have at least 1 parent born in the USA . Those who were lost to follow up were less likely to have at least 1 parent working full-time .

There were no differences between the analytic sample and those lost to follow-up in parental education, birth in the USA, and parenting style.A minority of the sample reported engaging in risky behaviors . At 11th grade, 15% reported using alcohol and 11% reported using cannabis in the last 30 days. One-fifth reported engaging in one or more alcohol misuse behaviors in the past year,such as drinking alcohol at school, getting into trouble because of alcohol, or missing school because of alcohol use . Sixteen percent reported engaging in similar cannabis misuse behaviors . One-fifth of the sample also reported engaging in one or more delinquent behaviors in the last year such as stealing, graffiti, selling drugs or being in a gang. One in eight students reported either carrying a weapon in the last 30 days or being in a physical fight in the last 12 months. Approximately 9% of students reported engaging in high-risk sex. Nearly one in five reported being the victim of bullying and 15% reported bullying others in the last 12 months. Among respondents, 22% of students reported being truant. From the start of 9th grade to the time of 11th grade survey, 23% of students reported changing schools at least once. Mean high school GPA was 2.83 , 35% and 71% of students were proficient in Math and English on 11th grade standardized tests respectively, and 43% matriculated at a 4-year college after high school.In the process of displacing millions of adolescents from school settings across the nation and the world, SARS-CoV-2 has reminded parents and policymakers alike of the irreplaceable role schools have in adolescent growth and health. It has also reinvigorated interest in the importance of the social climate that each school cultivates. These findings add longitudinal evidence that student reported metrics of school climate – including an orderly environment, teacher-student relationships, and disciplinary style – are important upstream predictors of both health and academic outcomes in subsequent years. Departing from the current literature that tends to isolate one or two school climate variables and outcomes, this analysis took a comprehensive approach in analyzing the longitudinal relationship between multiple school climate variables and an array of both health and academic outcomes. This permits a more holistic analysis that better captures the effect of a multifaceted school climate not just on cognitive development but also on health and behavioral development. While perceptions of school order and teacher respect for students were protective for nearly all risky behaviors, perceptions of safety were surprisingly only associated with less bullying. This supports some researchers’ assertion that, except in the case of bullying, school safety is only inconsistently protective for many outcomes. Similarly, perceptions of order and teacher respect for students was beneficial for a number of academic outcomes. Yet surprisingly, teacher support for college was not linked to any of our objective academic outcomes. Other authors have attributed such divergences to variations in measurement, however, as yet unidentified modifiers such as cultural norms cannot be excluded. Aligning well with the literature, neglectful disciplinary style was associated with several serious and concerning behaviors as well as poor academic outcomes . In contrast, permissive disciplinary style was strongly predictive of English proficiency and college matriculation, providing additional evidence for the critical role of teacher support. 

The information given by the total ion chromatogram is limited because of its complexity caused by co-elution and background noise. Instead, single ion chromatograms of different mass to charge ratios were extracted for isolating peaks ofindividual compounds, while avoiding co-elution and background noise. The stacked SIC of different thermal degradation compounds or aerosolized components from vaping aerosols of a) pure VEA, b) the mixture of VEA and extracted THC oil, c) extracted THC oil were shown in Figure 4.2. The black line represents the carbonyl/acids that can be generated from the thermal degradation of both VEA and extracted THC oil, the blue line represents the carbonyls/acids only from the thermal degradation of VEA, while the magenta line represents the thermal degradation carbonyls as well as cannabinoids only from the vaping aerosol of THC oil. Although the SICs were able to separate the co-eluting peaks with different m/z ratios, the isomers having identical m/z with similar structures and polarity are still not able to be separated or clearly identified. For example, multiple peaks are observed for C6H12O in the vaping aerosol of mixture of VEA and THC oil . While hexanal can be formed from terpenes, 97 4-methylpentanal could be formed from the thermal degradation VEA according to the proposed thermal degradation pathway in Scheme 4.1. However, since C6H12O is highly enhanced in the VEA aerosol , we assign the majority of this emission to 4-methylpentanal.Over 30 thermal degradation products from VEA were identified. All of the reported thermal degradation products from VEA are carbonyls/acids in this work, weed drying room consistent with other accounts. Riordan-Short et al. also identified several esters and alkanes with GC-MS .

While around 10 carbonyls and acids are identified both by us and Riordan-Short et al., carbonyls with VEA-specific structures have only been identified in this work. The lack of standard spectra for these VEA-derived compounds in GC-MS libraries may have prevented identification of peaks in the chromatograms of Riordan-Short et al.Moreover, some carbonyls identified by Riordan-Short et al. were not found in this work . The cause for discrepancy is unknown; however, we hypothesize it may be partially due to the difference in vaporization method .Many smaller thermal degradation carbonyls and acids appear to be formed by oxidation and bond cleavage of the aliphatic side-chain of VEA. The bond cleavage pathways for VEA degradation is proposed in Scheme 4.1. A proposed radical reaction mechanism is shown in Scheme 4.2. The thermal degradation reaction is initiated by H-abstraction by radicals such as OH, followed by the rapid reaction with O2 to form peroxy radicals . The peroxy radical can react with other RO2 to form carbonyls or alkoxy radicals. Alkoxy radicals may further react to form carbonyls , alcohols , and possibly alkenes . The primary thermaldegradation products may go through further oxidation steps and form more thermal degradation products . These RO2 –based mechanisms have been well studied and shown to be important in various chemical systems, like the atmosphere, biological redox, or fuel combustion. The relative peak intensity of carbonyls in Figure 4.2a support the proposed radical reaction mechanism in Scheme 4.2, since the most abundant peaks represented the formation of benzylic radical and tertiary radical formed in the first H-abstraction step which can be stabilized by the conjugation effect from benzene ring and positive hyper-conjugation effect from the adjacent C-H bonds. The proposed thermal degradation pathway is also supported by the detection of alkanes, including 2,6-dimethyl-1-heptene and 1-pristene, by Riordan-Short et al. and Mikheev et al., since these alkanes are generated in the proposed mechanism. Thus, our observations suggest that the C-C single bonds on the side-chain of VEA is easily oxidized and cleaved during the vaping process, which will cause the formation of a series of carbonyls that has VEA-specific structure, and also alkenes and alcohols.

These primary products may go through further thermal degradation process to generate secondary thermal degradation products like acids and dicarbonyls. Regarding products like duroquinone, durohydroquinone and ketene that have been identified previously by vaping or heating VEA we could not identified ketene as the it will form the same adduct molecular structure as acetic acid when reacting with 2,4-DNPH. We did not observe duroquinone for unknown reasons, possibly due to the difference in sample collection and methods of detection. Figure 4.2c shows the stacked SIC of vaping aerosol of THC oil. Besides thermal degradation carbonyl compounds, a large variety cannabinoids was also identified by HPLC-HRMS, since the phenolic hydroxyl group in cannabinoid structure is slightly acidic and can also be deprotonated in the negative mode of ESI. The thermal degradations products identified in the vaping aerosol of extracted THC oil may not only generated by THC, but can also from the thermal degradation of other cannabinoids, such as cannabinol , cannabidiol , cannabichromene , cannabigerol and corresponding acid , which have also been identified in the unvaped extracted THC oil. The mechanism of the production of carbonyls identified in the vaping aerosol of extracted THC oil may also involve the oxidation of the aliphatic side-chain followed by bond cleavage, since the main cannabinoids also have the side-chains with 5 carbons.Moreover, CBG may be the source of certain carbonyl products since it has a second side-chain with unsaturated bonds ; the specific mechanism is shown in Scheme 4.4. In contrast to VEA, the oxidation of CBG by OH proceeds through addition to the double bonds in the side chain instead of H-abstraction, consistent with the oxidation of other alkenes. The mechanism for the following steps are similar to the H-abstraction route.

The oxidation may also occur on the six member ring of cannabinoids such as THC can occur through pathways proposed in Scheme 4.3b and Scheme 4.5. For example, OH-initiated H-abstraction on THC can occur at the allylic site and OH-addition can occur at the endocyclic C=C, preferentially forming the tertiary alkyl radical. Then peroxy radical chemistry occurs through similar pathways as VEA, finally generating alcohols and potentially epoxides. Multiple SIC peaks are found at the m/z representing oxidized products of cannabinoids, suggesting a lot of different isomers exist. Our identification results are similar to those of Carbone et al., who utilized NMR for identification. Carbone et al. indicated peroxide products may also be formed during the oxidation process, a mechanism not shown in our schemes but would be consistent with RO2 chemistry. The oxidation products shown in Scheme 4.3b have the same number of carbons as THC; however, some thermal degradation products with different carbon numbers were also identified and are hard to trace back to precursor compounds. It is possible they may already exist in the original unvaped THC oil. Borille et al. found cannabinoid compounds or metabolites and 8 non-cannabinoid constituents in the extracts of cannabis plants by ESI-MS, with carbon number of cannabinoids range from C15 to C55. All molecular formulas of the THC oxidation products shown in Scheme 4.3b were also identified in cannabis extracts, suggesting that these components may already exist in the cannabis plant, and that oxidation from plant metabolism or during extraction couldhave occurred in addition to vaping. Moreover, the C19H28O3 has been identified as Cannabiglendol-C3 ; and there exist many possibilities for C23H34O4 ; C15H16O3/C15H18O3 had been identified as cannabispirenone/ cannabispiran. Some compounds in Table 4.1 still remains unidentified .Besides the oxidation products from vaping THC oil, for which the oxidation mechanism is described in Scheme 4.3, there remains unexplained formation pathway for the generation of some thermal degradation products . Couch et al. found the risk of exposure to VOC including diacetyl and 2,3-pentanedione during the decarboxylation and grinding process of dried cannabis material, but there is no clear mechanism given for their formation. The generation of these compounds may due to the thermal degradation of terpenes and terpenoids. Since there is still over 50% mass in the unvaped THC oil that remains uncharacterized, drying rack for weed it is likely that a portion of that mass are terpenes. Meehan-Atrash et al. identified degradation products from myrcene, limonene and linalool, including methacrolein, hydroxyacetone, methyl vinyl ketone. Tang et al. found 11 thermal degradation products from mixture of terpenoids, 7 of them are carbonyls including formaldehyde, acetaldehyde, acetone, acrolein, methacrolein, valeraldehyde and hexanal. These findings are consistent with the identification results in this work, illustrating that the extracted THC oil is a complex mixture, the complexity of which increases with thermal degradation chemistry. Further research on individual components is still needed for a better understanding on the whole picture of thermal degradation. For the mixture of THC oil and VEA, it is clear from the stacked SIC that the peaks shown in the chromatograph are mainly from aerosolization products of vaped THC oil instead of VEA. It is clear that the total signal from aerosolization products of the mixture is between that of vaping pure VEA and THC oil. Moreover, the oxidation of THC may also be suppressed by adding of VEA. While the signal ratio of cannabinoids in vaping aerosol of the mixture compared to unvaped THC oil is 0.34, the same ratio for oxidated cannabinoids in Scheme 4.3b is 0.22 .

THC was shown tohave a stronger tendency to degrade compared to VEA, since the boiling point for THC is 157 ˚C, while VEA start to decay at 240 ˚C without boiling. Table 4.2 shows the particle mass collected on the glass fiber filter at three temperatures and various e-liquid composition. It is clear that increasing temperature will increase the particle mass on the filter, which is consistent with expectations. However, the particle mass production is non-linearly suppressed with the addition of VEA compared to THC oil at the same temperature. The reason might be the formation of non-ideal solution with significant intermolecular interactions when VEA is added to the THC oil, as Lanzarotta et al.  had found that hydrogen bonding exists between the molecules of VEA and THC. Given the fact that THC has a much higher aerosolization rate compared to VEA , the cartridge may be enriched in VEA since vaping continues until it is 100% VEA. In order to figure out the influence of VEA to the formation of carbonyls, it is informative to normalize the mass of carbonyls by the particle mass collected at the same temperature . While e-cigarette users who used nicotine products will self-titrate nicotine intake in daily use, there is also evidence that people who use higher potency cannabis for recreational purpose can titrate their THC dose. Figure 4.4 shows the normalized mass of 9 thermal degradation carbonyl compounds by particle mass produced from vaping VEA, THC oil and their mixture at 455 ± 10 °F . Within the C4 – C6 carbonyls shown in Figure 4.4, butyraldehyde, valeraldehyde, hexanal are thought to be from the thermal degradation of cannabinoids and terpenes , supported by Tang et al., while isobutyraldehyde, isovaleraldehyde and 4-methylpentanal are from the thermal degradation of VEA , supported by RiordanShort et al. Since some isomers can’t be separated in this work, we discuss the pair of isomers together. From the normalized carbonyl concentration, it is clear that certain carbonyls such as formaldehyde, hexanal/4-methylpentanal, glyoxal, diacetyl/3-oxobutanal are produced in much higher abundance from VEA compared to extracted THC oil. Although some products like formaldehyde can be produced from both VEA and THC, the production of formaldehyde from VEA is more favorable since it involves a tertiary radical intermediate in the first step , which is more stable than the secondary radicals formed from the side-chain of THC. The proposed chemistry is, thus, consistent with higher formaldehyde formation by VEA. The same explanation can also apply to the generation of 4-methylpentanal, which only comes from VEA and thus likely dominates the distribution of the isomer pair over hexanal. The formation of glyoxal, diacetyl and 3-oxobutanal from VEA likewise may be enhanced compared to THC due to higher stability of radical intermediates. Diacetyl is thought to be byproducts of cannabis plants,61 and there is no clear indication of formation of diacetyl from VEA . The formation of its isomer 3-oxobutanal can be expected from VEA, however. The corresponding SIC of diacetyl shows that multiple peaks exists in the vaping aerosol of extracted THC oil, but only one peak shown in the vaping aerosol of pure VEA, suggesting that cannabinoids and terpenes may generate multiple isomers which have the same m/z as diacetyl, but VEA propably generates only 3-oxobutanal.

In addition to thermal degradation products, flavoring chemicals are also found to be significant components in e-cigarette aerosol. Allen et al. 53 measured the concentration of diacetyl , 2,3-pentanedione , and acetoin in 51 e-cigarettes from different brands and flavors, with the highest concentrations found for e-liquid flavors such as “Peach Schnapps.” In this work, the estimated concentrations of the flavoring chemicals diacetyl , 2,3-pentanedione , and acetoin are fairly consistent with some measurements for the Classic Tobacco flavor but higher than others. Of note is that Klager et al. found diacetyl concentration in 16 different e-cigarettes varies from 0.028 – 3.69 µg/m3 , while our results show a concentration of 56 ±15 µg/m3 . It is clear that the amount of flavoring chemicals largely depend on the individual e-liquids, puffing regimen, and collection methods. In addition, two carbonyl flavoring additives have been quantified here for the first time in ecigarette aerosol. Acid additives are used to control the acidity of eliquids. Inhaling either diacetyl, or the related flavoring 2,3-pentanedione, has been associated with bronchiolitis obliterans . As the composition of e-cigarette aerosol is complex and the range of products is vast, a more systematic understanding of the fundamental chemistry is needed.Electronic cigarettes are battery-operated devices used to “vape” or aerosolize “e-liquid” consisting of propylene glycol , vegetable glycerin , nicotine, and optional flavor compounds. The global market share of e-cigarettes is rapidly growing, and e-cigarette use among young people has become a significant public health concern. Of U.S. high school students and middle school students, 27.5% and 10.5%, respectively, self-reported usage for one or more days during the past 30 days in 2019. The design of the e-cigarette has rapidly evolved from 1st generation “cig-a-like” pods with disposable, prefilled, curing cannabis e-liquid cartridges and fixed operational parameters , to 3rd generation “mods” with a refillable e-liquid tank and adjustable device operational parameters.

More recently, 4th generation“mod-pod” hybrids with fixed power output have been released. E-cigarettes gas and particle emissions are composed of aerosolized PG, VG, optional flavors, and nicotine from the e-liquid, as well as free radicals, and a variety of carbonyls or hydroxycarbonyls formed by thermal degradation during the e-liquid heating process. Recent evidence suggests hydroxycarbonyls may be more abundant than anticipated, but their impacts on health remain poorly understood. With the ability to change vaping parameters , coil material, and e-liquid formulations in 3rd and 4th generation devices, there exists a multitude of use combinations that can influence the composition of the inhaled e-cigarette aerosol. In particular, aerosol composition and gas/particle partitioning could greatly influence the risk of chemical exposure and aerosol deposition in the human respiratory tract. However, the ways in which e-liquids form aerosol components under different vaping parameters have not been fully elucidated in the literature. Coil temperature and e-liquid composition will directly affect e-cigarette aerosol emissions, as heating e-liquid solutions with metal coils results in thermal degradation reactions and changes in aerosol concentration. The majority of published studies have correlated e-cigarette emissions to device voltage and power, but not directly to the vaping coil temperature that governs the thermal degradation process. For example, Korzun et al. inferred coil temperature by airflow rate, and found higher temperatures led to higher concentrations of formaldehyde and acetaldehyde by promoting the degradation of higher molecular-weight products such as hydroxyacetone and glycoaldehyde in the product mixture.

Uchiyama et al. evaluated the phase distribution for a number of compounds, and found the formation of degradation products from vaping exponentially increased when the device power exceeded 40 W. However, a direct comparison between such studies is challenging. This is because the actual coil temperature is synergistically influenced by many factors, some of which are inherent to the coil, while others are a result of the conditions of operation. For example, different coils may have different resistances due to material and structural variance. Furthermore, coil temperature may also be influenced by e-liquid composition, which changes the viscosity and heat capacity, or by air flow rates in the device, as faster air flow rates have higher cooling effects. Thus, a single vaping device may produce different temperature ranges for the same voltage input upon minor alterations in operational scenarios.In addition, the aerosol emissions will change as a result of the users’ puffing regimen. Bitzer et al. showed puff volume and duration influence the per-puff yield of nicotine, carbonyls, aerosols, and free radicals. Beauval et al. also found modifications in puffing conditions lead to significant variations in the carbonyl composition of e-cigarette aerosols.However, there remain a number of questions concerning the fractions of PG and VG in the total e-liquid that convert to degradation products, the specific chemical mechanisms of transformation, and the ways in which e-cigarette chemical components partition between phases in response to changing vaping parameters.Thus, a systematic understanding of how the carbon mass balance and chemistry of the vaping process respond to changing e-liquid formulation, major puffing parameters, and actual coil temperatures is critically needed. Monitoring coil temperature instead of voltage/power as a standard evaluation metric may provide greater fundamental insights into the chemistry.

However to do so, the coil temperature will need to be directly measured during each puff, as the temperature-controlled programs of e-cigarette devices may not be a true reflection of the actual coil temperature. In the present study, a broad chemical analysis suite, volatility-based aerosol sampling, and direct measurement of coil temperatures were employed to study the aerosol emissions from a 3rd generation e-cigarette device at various coil temperatures, puff durations, and PG:VG ratios in the e-liquid solution. Flavoring compounds were deferred for future research. The loss of mass from the e-liquid conversion to aerosols was compared with independent measurements in the particle and gas phases for carbon mass closure analyses.E-cigarette aerosols were generated using a 3rd generation Evolv DNA 75 Color modular vaping device with replacement single mesh vaping coils that have a coil resistance of ca. 0.12 Ohm. The stainless steel coil was selected as only limited coil materials are appropriate for temperature control. The device has a rechargeable battery with a variable output voltage and power , an atomizer coil assembly, a refillable e-liquid tank that enables eliquid with variable formulations to be tested, and a push button to initiate puffing. The device was robotically operated by a custom linear actuator during the puffing proces s, which enabled precise control of the puff rate and puff duration with a ±3% standard deviation . Evolv Escribe software was used to set the power and temperature conditions to achieve the desired coil temperature , as measured by a flexible Kapton-insulated K type thermocouple in contact with the center of the coil surface, cannabis dryer and output to a digital readout. The puff flow rate was 1.186 ± 0.002 L/min, and the corresponding puff volume for a 3-s puff was 59.3 ± 0.1 mL, as quantified by a primary flow calibrator . The puff volume and duration selected for this study is consistent with the CORESTA e-cigarette testing protocol .

However, puff volume larger than 100 mL and puff duration longer than 3 s have been observed in some vaping scenarios. For example, Robinson et al. found a typical case of puff topography with 3.7 s puff duration and 144 mL puff volume. Thus, this highlights a limitation of the current study when extrapolated to various vaping scenarios, as an increase in the puff volume will increase the formation of aerosol and thermal degradation compounds.167 The puffing protocol for the puff duration study is not based on volume, but used a variable puff duration at a fixed flow rate. Table 3.1 shows the experimental conditions used in this work. Pure VG, PG, and nicotine were used to generate e-liquids at the ratios and concentrations shown in Table 3.1. Particles were collected on a hydrophilic polytetrafluoroethylene membrane filters . PTFE and other types of filters have been used in sample collection for e-cigarette research. As hydrophobic filters were found to be incompatible with the polar compounds in e-cigarette aerosol, the hydrophilic PTFE filters were chosen for use because they have broad compatibility with both polar and non-polar functional groups. Both the gas phase of total aerosol stream and the particle filters were analyzed for mass and chemical composition. The total mass lost from the e-liquid due to vaping was determined gravimetrically on a microbalance by weighing the e-liquid compartment immediately before and after puffing 10 puffs, and dividing by the number of puffs at different experimental conditions. The standard deviation of the gravimetric analysis after triplicate measurements was determined to be ~ 20%, mainly due to variations in puffing. The composition of gas phase PG/VG, was analyzed by chemical ionization triple-quadrupole mass spectrometer ; a detailed description can be found in Section 3.2.4. The particle mass on the filter was analyzed after each collection on the microbalance, also performed in triplicate. The total mass of molecules residingin the gas phase was determined as the difference between the total mass of e-liquid lost and the mass of the particles collected.E-cigarette aerosols are known to be semivolatile at room-temperature, i.e., the chemicals can exist in both gas and particle phases under various conditions , and are highly unstable mixtures that undergo continuously change of size, number concentration and chemical composition by coagulation, evaporation/condensation of individual components, wall deposition and potentially water uptake. Thus, there is no perfect sampling protocol for such a dynamic mixture. Sampling with particle filters may either underestimate or overestimate total non-volatiles. Underestimation may occur if fine particles break through the filter. Overestimation could result if the filter has a higher surface area than in realistic vaping scenarios, or if the filter is saturated with an organic film, into which the semivolatiles can partition during sampling. Our particle size distribution analysis with a scanning mobility particle sizer that measures a size range of 0.014 – 0.671 µm diameter showed that particle breakthrough for Omnipore filter at a 0.2-µm pore size may not be significant for this work. However, the diameter of aerosol will go through a size change process caused mainly by coagulation and evaporation that could occur during the aerosol collection and measurement steps. Zhang et al.231 found that the count median diameter of e-cigarette aerosols is 120 – 180 nm when counted immediately after emission from the e-cigarette. The CMD changes to 400 nm for the measurement of droplets at steady-state. Furthermore, we confirmed that the collection efficiency for the filter was > 97.5% based on consecutive collections in series. Thus, we believe this method minimized the possible underestimations of the particle phase. We then tested a denser structure or higher surface area particle filtering material. A high-flow High Efficiency Particulate-free Air capsule upstream of our chemical analyses removed 99.9% of all particles . However, the HEPA capsule also removed 50-100% of gaseous formaldehyde, hydroxyacetone, acetone, acetaldehyde, and dihydroxyacetone gas standards that were evaporated and diluted directly into a 100-L Teflon FEP bag using chemical standards, which would overestimate the particle phase. For the purpose of this work, particles that are trapped by hydrophilic PTFE filter are termed the “nonvolatile ” or “particle” fraction and the difference between the total aerosol and the NV fraction is termed the “volatile/semivolatile” or “gas” fraction. Although particles are termed nonvolatile, it does not mean that they cannot partition to the gas phase under conditions different than the ones we tested . Likewise, semivolatiles emitted in the gasphase directly from the mainstream can condense onto surfaces that have higher condensable surface area than used our study.The particle filters were analyzed by an Agilent 6890N gas chromatograph coupled to an Agilent 5973N quadrupole mass spectrometer . Filters were extracted by a 10-mL 1:1 mix of methanol and ethyl acetate . The method for the analysis of PG, VG, and nicotine was adapted from Williams et al.232 The components were separated on a DB–wax capillary column with ultra-high purity grade Helium at a constant flow of 1.1 mL/min. The temperature program was 50 °C , 8 °C /min to 160 °C, 5 °C /min to 170 °C, then 170 °C . Electron impact mass spectra for PG, VG, and nicotine were > 90% matched to the National Institute of Standards and Technology database. PG, VG, and nicotine standards were used for GCMS calibration.

Milwaukee’s urban agriculture organizations have worked to secure longer leases for community gardens, but they have not succeeded in purchasing and preserving many of the sites, so most of the city’s gardens remain vulnerable to development. The gardens that exist today are generally clustered around the Near North Side, where poverty, unemployment, and food insecurity are high and development pressure has remained low. Based on the demographics of the Near North Side, the people most likely encounter the city’s gardens are low-income Black residents, however my spatial analysis revealed that gardens associated with citywide programs are also relatively more accessible for neighborhoods with higher rates of Hispanic and Asian/Pacific Islander residents than for neighborhoods that are largely white. These gardens appear to be concentrated where the greatest economic need is, but if development pressure in the disinvested neighborhoods were to increase, the gardens will be vulnerable to displacement. In Philadelphia, development pressure has increased quite dramatically in some neighborhoods, displacing gardens and residents alike. PHS’s effort to concentrate greening interventions in specific neighborhoods has proven the revitalization potential of urban agriculture. However, this revitalization focus seems to limit the benefits for the city’s poorest residents. Based on my spatial analysis, the program’s gardens are likely to be closer to neighborhoods with lower poverty rates and higher housing costs . Neighborhoods with more Black and Hispanic residents are more likely to have a garden nearby, cannabis growing equipment but the racial composition of many neighborhoods has also been in flux as property values rise, and Black residents appear to be gradually losing access to gardens in this process.

In Seattle, through the concerted effort of P-Patch program and nonprofit leaders seeking to maintain the program’s legitimacy, gardens have become more accessible for the city’s low-income communities over time. However, they have also become less accessible for immigrants, reflecting a pattern in all three cities where many foreign born residents seem to lack convenient access to programmatic gardens. Moreover, in Seattle the increasing access for high-poverty neighborhoods belies the fact that many people in poverty have been forced out of the city altogether, as property values have risen precipitously in recent years due to Seattle’s status as a world-class creative city—a reputation bolstered by the secure, widespread presence of P-Patch gardens. Thus, someone encountering a garden in Seattle today is more likely to have a high income, and while they might appreciate the social, environmental and aesthetic benefits of the garden before them, there are thousands of other people missing out on that experience because of the city’s changing economic condition. The individuals moving through the socio-environments in these three cities are unlikely to directly see the organizations that have helped to build and protect the city’s cultivated spaces, but as this dissertation shows, organizations in all cases have clearly played a role in shaping the flows of materials, ideas and people that converge to make urban agriculture and urban life more broadly. Electronic cigarettes , sometimes referred as “e-cigs”, “e-hookahs,” “vape pens,” and “electronic nicotine delivery systems ”, are rechargeable electronic nicotine delivery devices that are alternatives to smoking tobacco cigarettes. E-cigarettes consist of four parts: an atomizer , a battery, an e-liquid reservoir and an electronic control system. The atomizer heats and aerosolizes the e-liquid during the “vaping” process when the user takes a puff or presses the button; this generates a nicotine-containing e-cigarette aerosol that will be inhaled by the user for the purpose of nicotine intake.

Unlike traditional tobacco products, there is no combustion in the use of e-cigarettes, which eliminates the intake of tar and other harmful and potential harmful chemicals generated through cigarette or cigar smoking. In addition, the tar generated through conventional smoking which is extremely toxic to human and damages the smoker’s lungs through biochemical and mechanical process over a long time period 7-9 can also be eliminated through e-cigarette use. To date, e-cigarettes have been widely regarded as a “less harm” alternative to traditional cigarettes that can be used to help smoking cessation. However, the controversy of e-cigarette use has been increasing in recent years, since the beneficial link between e-cigarettes and smoking cessation is debated and emerging health issues had been found, related to the use of different kinds of e-cigarettes. It is noteworthy that thermal degradation products have been characterized due to the vaping process, some of which are known to have negative human health effects. The development of a nicotine aerosol generation device started in 1963, while the modern ecigarette was invented by a Chinese pharmacist Han Li, who thought of vaporizing nicotine containing propylene glycol using a high frequency ultrasound-emitting element, causing a smoke like vapor. E-cigarettes was first introduced to Chinese market starting from 2004, then entered the European and the US market in 2006 and 2007. The later design of the e-cigarette has changed from the earlier ultrasonic vaporization method to a battery-operated heating element. E-cigarette device design has evolved significantly since its introduction. The first-generation e-cigarettes use fixed and low voltage batteries, with a physical appearance similar to combustible cigarettes and are often referred to as “cig-a-like”. There exist two versions of the first-generation e-cigarette on the market, one is a two-part design, in which the replaceable atomizer and e-liquid reservoir are in one part, while the battery is separated in another part. The second style combines the atomizing unit, e-liquid reservoir and battery into one part. The first-generation product is still widely sold on the market. The second-generation e-cigarette typically has a larger variable voltage battery with a device referred to as a “clearomizer”. It has a removable atomizing unit with a filament, separated into a e-liquid reservoir and battery. The e-liquid tank of the second generation device has a larger volume reservoir compared to first generation systems, and can be refilled with different e-liquids. The third-generation e-cigarette, known as the “Mod”, has modified batteries that is able to vary the device power, voltage and, thus, temperature. It has a removable atomizing unit and larger e-liquid tank compared to the original clearomizers. 

The Sub-Ohm tank with low resistance coils in atomizers is highly customized, as it is designed to create a large cloud with a strong delivery of nicotine and other additives. Stainless steel, nickel and titanium are typical materials used for the coil in third-generation devices, as these materials enable linear temperature changes with the adjustment of device power output. The fourth-generation e-cigarette is referred to as “Pod-Mods”, and contains a prefilled or refillable “pod” cartridge with a modifiable system. The compatible prefilled pod cartridges usually contain nicotine with PG/VG, THC or CBD as oils, and flavoring compounds. In addition to e-cigarettes, an inhalation device called a “vaporizer” is also available on the market; it applies non-combustion heat to aerosolize dry herbs or oil to release the active substance in these materials without combustion. Moreover, “dabbing” or “dibbing” is a specific term that describes the action or practice of inhaling small quantities of a concentrated and vaporized drug, cannabis drying trays typically cannabis oil or resin. It usually simulates the aerosolization process by placing the extracted THC oil concentrates on a hot surface. Since its first commercial introduction to the United States, sales in the e-cigarette industry has increased to $3.5 billion by 2015. The e-cigarette industry has greatly impacted the use of new tobacco products among youth. The prevalence of e-cigarette use among high school students increased from 1.5% in 2011 to 16% in 2015, which surpasses the prevalence of conventional cigarette use among high school students. According to a report by the Centers for Disease Control and Prevention in 2020, 19.6% of high school students and 4.7% of middle school students reported current e-cigarette use. Among current e-cigarette users, 38.9% of high school students and 20.0% of middle school students have used e-cigarettes on 20 or more of the past 30 days; 22.5% of high school users and 9.4% of middle school users reported daily use. Among all current e-cigarette users, 82.9% used flavored e-cigarettes. Investigators conducting toxicology and human health studies of acute and chronic use of e-cigarettes are struggling to keep pace with e-cigarettes’ popularity and product changes. The study of the health effects of these products is complicated by the fact that there are hundreds of e-cigarette devices and thousands of commercially-available e-liquids available to consumers. Further, the new generations of e-cigarettes have increased the flexibility of use for consumers by allowing any e-liquid to be added to the tank and a large range of variable power settings, which can increase the temperature of the device, as well as the output of vapor/aerosol and delivery of nicotine.

The composition of typical regular e-liquid for nicotine delivery usually include propylene glycol , vegetable glycerin , water, nicotine, and flavoring additives. PG and VG are typically used as solvents in order to produce an aerosol that simulates cigarette smoke. PG is a transparent and viscous liquid at room temperature with a sweet taste. It has very low volatility with a boiling point of 188 °C. The use of PG is generally regarded as safe for oral consumption, and it is usually used as a humectant and preservative in food, tobacco and the personal care industry. Moreover, PG is also used in the pharmaceutical industry as a solvent for drug delivery. Although it is widely used, the toxicology at a high concentration is increasingly recognized and recently reported. VG is a colorless and odorless viscous liquid with a boiling point of 290 ℃. It also has low volatility and a sweet taste, serving as a humectant, solvent, and sweetener in food, pharmaceutical and personal care applications. Both PG and VG have multiple hydroxyl groups,which results in the strong intermolecular force in the e-liquid and e-cigarette aerosol by forming multiple hydrogen bonds. Vaporization of PG and VG requires a relatively high temperature, although PG and VG start decomposing within the temperature range of e-cigarette use. The ratio of PG and VG in e-liquid varies in different products based on whether flavor or more aerosol mass or “cloud” is desired, while the most common two ratios are 50% PG/50%VG and 70%VG/30%PG. E-liquids containing more PG delivered more nicotine to these e-cigarette users. The chemical structure of PG and VG are shown in Scheme 1.1a. Nicotine is a chiral alkaloid produced in the nightshade family of plants, which has been widely used as recreational or anxiolytic compounds. Nicotine is a highly addictive compound that acts as receptor agonist for nicotinic acetylcholine receptors; its binding strength is better than the neurotransmitter acetylcholine. Therefore, nicotine is the equivalent to an increase in the amount of neurotransmitters, which results in increased secretion of dopamine from the reward center of the human brain. The average amount of absorbed nicotine per cigarette is about 2 mg, while the nicotine content of commercially available e-liquids varies from low to high . The chemical structure of nicotine is shown in Scheme 1.1b. Beside PG, VG and nicotine, most e-liquids contain flavor chemicals that have been certified as safe for ingestion in the food industry. The use of flavor compounds to create various flavor combinations is attractive to consumers. There are various chemical families of flavorants used on the market, including aldehyde , ketone , alcohol , monoterpene and ester . Animportant category is aldehyde, which has been recognized as “primary irritants” of the mucosal tissue of the respiratory tract. Behar et al. has identified that the most commonly used flavoring chemicals are menthone, p-anisaldehyde, menthol, cinnaldehyde, vanillin, and ethyl maltol, which has been found in 41 – 80% of commercial e-liquids. The transfer of these flavoring chemicals from e-liquid to e-cigarette aerosol is very efficient , while it has also been found that the refilled fluids that have lower concentrations of flavoring chemicals exhibit lower cytotoxicity, suggesting the toxicity of the e-cigarette aerosol is related to the concentration of theflavoring chemicals. However, with the significant increase in the array of different e-liquid products, it is difficult to comprehensively characterize all flavor compounds on the market. Previous research found flavor chemicals to be 1-4% of the total e-liquid volume, although the concentration of some specific flavor chemicals were sufficiently high enough to possibly be of concern for inhalation toxicology. Some specific flavoring chemicals like diacetyl has been found to cause adverse health effects to e-cigarette users, even if they are safe to digest.

Assessing the socio-demographic dynamics of urban agriculture development in New York City, Reynolds notes that while low-income communities, immigrants and people of color often bring significant knowledge, energy and enthusiasm to the development and maintenance of gardens, these groups tend to have less access to the resources, networks and cultural capital required to build and defend community gardens in the urban landscape. As earlier chapters have demonstrated, in order to attract resources and legal status for their gardens, community garden programs must legitimize themselves according to some of urban agriculture’s potential benefits at the expense of others. In all three cities, urban agriculture advocates have made claims about the role of gardens in helping people in need, but they have also emphasized arguments about the economic benefits of community gardens. Economic benefits like neighborhood development and elevated property values can be in tension with serving the needs of the marginalized, whose interests are often left behind in the flow of capital through cities . On the one hand, community gardens may be easier to establish where vacant land is more abundant, that is, in neighborhoods with depressed property values—often those with higher proportions of people in poverty, immigrants, and/or residents of color. On the other hand, marginalized communities may have a harder time marshalling the resources needed to defend community gardens from rising property values and increased neighborhood development, if and when these potential economic benefits of urban agriculture materialize. This tension is ubiquitous in urban agriculture . However, ebb and flow flood table researchers have to date paid little attention to the role that citywide community gardening organizations can play in mitigating neighborhood inequalities by amassing and equitably distributing the resources needed to build, maintain, and defend urban agricultural spaces.

In this chapter, I draw on historical datasets developed from review of organizational documents for each city to conduct a longitudinal spatial analysis of garden accessibility. To fully understand who is benefitting most from community gardens, multiple types of data ought to be considered. Ethnographic research or extensive surveys would be needed to determine who is actually using the gardens within a program, how much nutritional, recreational, social and cultural benefit participants are receiving, and what collective benefits the local community is realizing from the presence of a garden. With the exception of a few documents summarizing survey results from Seattle’s P-Patches in the 1990s, my data do not provide this type of detail about usage or measured outcomes. However, extensive review of the historical documents from each program does enable another important approach to understanding equity in garden access: the proximity of gardens to different neighborhoods. Mapping the gardens that each program invested in over time and using spatial analysis to assess the gardens’ accessibility to marginalized communities, we can understand the historical trajectory of each program’s impact on the urban environment, a perspective that would not be possible with ethnographic or cross-sectional survey methods. A spatial approach is especially relevant for understanding urban agriculture as a land use as well as a social practice. Urban researchers have used spatial analysis to assess whether community gardens are alleviating food deserts and to identify the neighborhoods in a city which would benefit most from urban agriculture , but have yet to analyze the extent to which existing community gardens in a city actually serve the neighborhoods with the highest need.

In this chapter, I first summarize the methodology used to map the gardens in each city over time. Then, I describe the results of my spatial analysis in detail, connecting them to key points from the qualitative historical analysis laid out in preceding chapters. I conclude by highlighting the ways that organizational decisions over time are evident in how gardens are and have been distributed across each city.In order to show how the citywide gardening programs in Milwaukee, Philadelphia and Seattle have expanded over time and how accessible their gardens have been to marginalized communities, I built an original historical dataset2 , mapped the gardens that were associated with each program in 1980, 1990, 2000, 2010, and 2019, and conducted a series of spatial analyses on the relationships between garden locations and neighborhood demographic characteristics. During my review of documents from the main garden programs in each city, I compiled a database with the name, location, and years active for each garden mentioned over the programs’ histories. Records such as annual reports and garden maps tended to provide complete snapshots of the gardens included in a program at a particular time, while newsletters and newspaper articles offered supplementary information to date the creation or closure of some gardens. Together, the documents available for each city furnished enough information for a detailed, if not perfectly complete, picture of how the programs expanded in urban space as their budgets grew and they were able to develop new gardens—and how and where the programs contracted under the pressure of changing budgetary or real estate market conditions.In order to understand the relative accessibility of each programs’ gardens for marginalized groups, I acquired neighborhood demographic information for each city at the Census tract level. Using Geolytics, I downloaded a dataset with relevant variables for 1980, 1990, 2000, and 2010 fit to the 2010 Census boundaries. Using the software program R, I then downloaded equivalent values from the 2015-2019 American Community Survey . Given the salience of urban agriculture’s potential benefits for immigrants, low-income and people of color, I obtained counts and calculated percentages for each tract’s poverty rate, percent foreign born, percent nonHispanic white, percent non-Hispanic Black, percent Hispanic, and percent non-Hispanic Asian or Pacific Islander.

Census questions about racial and ethnic categories have changed slightly over the last 50 years, and the groups above were chosen for this study because they can be calculated consistently across the 5 decades of interest while speaking to the patterns of racial inequality and marginalization most commonly observed in US cities. Because the ability to create, maintain and preserve community gardens is influenced by socioeconomic characteristics such as real estate values and supporters’ cultural capital, I also obtained tractlevel data on education levels , median household income, and median monthly housing costs. After compiling a dataset with the independent variables of interest for the 2010 Census tracts across all 5 decades, I calculated measures of garden accessibility for each Census tract in each decade. I used the Google API to geocode the garden addresses into latitude and longitude, and then georeferenced the coordinates to align with the Census tract coordinate reference system. Overlaying the gardens’ geographic information onto the 2010 Census tracts, I obtained counts for the number of gardens in each tract in 1980, 1990, 2000, 2010 and 2019. Since most tracts had zero gardens and very few had more than one, this measure had significant skew; I then created a binary variable indicating whether a tract contained at least one garden in a given year. There is a great deal of variation in the size of Census tracts, hydroponic drain table and the boundaries between tracts do not represent firm restrictions on residents’ activities. To address these concerns, I created additional dependent variables based on distance rather than tract boundaries. For each tract and year, I calculated the distance from the tract centroid to the nearest garden, and I created another binary variable indicating whether at least one garden was within a one-mile radius of the tract centroid. Before mapping and modeling garden accessibility, I conducted exploratory data analysis to refine my variable specification. I ran correlations of all variables and found several strong correlations that risked weakening the models through multicollinearity. First, the two variables for education were strongly negatively correlated. I chose to model percent with a college degree and leave out percent with less than a high school education, given the role of cultural capital in successful creation and preservation of community gardens that earlier studies have identified . Next, median household income was strongly positively correlated with housing costs and strongly negatively correlated with poverty rates, but the correlation between housing costs and poverty rates tended to be much weaker. I chose to include housing costs and poverty rates in the models while removing household income to reduce multicollinearity.

Retaining the poverty and housing variables, both the accessibility of gardens for low-income communities and the threat to gardens from high land values can be represented in the model. Due to a consistently strong negative correlation between percent white and percent Black, I chose to remove percent white from the models and retain focus on gardens’ proximity to people of color. I also found strong positive correlations between percent foreign born and percent Hispanic in Milwaukee and Philadelphia, and between percent foreign born and percent Asian or Pacific Islander in Seattle. Due to the theoretical importance of understanding garden accessibility both for racial minorities and for immigrants, I chose to retain all three variables in my models and test the outcomes when each of them was removed to see if multicollinearity was impacting the results.After testing for multicollinearity, I tested for spatial autocorrelation—that is, whether high or low values for any of the variables were clustered in adjacent Census tracts. For each city, I made three matrices defining neighboring tracts: queen contiguity, 2-nearest, and 3- nearest neighbor weights matrices. Then I calculated Moran’s I for all variables in each city and year, using each of the three neighbor weights matrices. Regardless of the matrix used, Moran’s I values were greater than 0.3 for almost all of the independent variables, indicating substantial spatial autocorrelation. In other words, neighborhoods show clustering in characteristics such as poverty rates, racial and ethnic composition, and education levels. This finding is unsurprising, given what we know of neighborhood effects and the legacies of residential racial segregation, yet it is important to note due to its potential impact on any spatial models. For all cities, years, and neighbor weights matrices, Moran’s I showed significant spatial autocorrelation in the distance based measures of garden accessibility . However, the tract-boundary measures of garden access had Moran’s I values close to 0 in Milwaukee and Seattle for all years, indicating that the gardens themselves are not generally clustered in these cities. Only Philadelphia appeared to have statistically significant clustering in the locations of gardens. Mapping the dependent variables for each city and year showed that much of the clustering in the distance-based measures of garden accessibility was due to a complete lack of gardens in certain areas of the city, where adjacent tracts logged progressively larger distances to the nearest garden. Figure 1 illustrates the typical appearance of this pattern, with the areas of northwest and south Milwaukee and northeast and south Philadelphia hosting zero gardens from their cities’ respective garden programs. The clustering of distance-based garden accessibility variables in Seattle is not as visible when mapped, but it nonetheless registered as significant in the Moran’s I tests for all neighbor weights matrices and years.Given that garden programs are working to administer multiple sites across a city with limited resources, the lack of gardens in far-flung regions may be understandable. Still, when large areas of a city remain unserved by a citywide program, the lack of service to these areas is notable. For this reason, I chose not to treat the far-flung tracts as “outliers” and remove them from the models altogether. However, in practical terms, the progressively larger distances to the nearest garden that result from this pattern can skew the dependent variable in a way that interferes with the overall model fit and accuracy. Therefore, I developed a “corrective” variable giving the distance from each tract centroid to City Hall, a measure approximating the resources required to travel to the tract from garden program offices5 . I chose to run models with and without distance to downtown in order to assess how well it corrected for skew from the far-flung tract values and whether it impacted results in any other way.Given the potential impact of multicollinearity and spatial autocorrelation on regression modeling, I ran a series of Ordinary Least Squares regressions and diagnostics to test the impact of controlling for distance to downtown, to assess the influence of correlations between race and immigration variables, and to determine whether OLS or spatial models would be more accurate.

These elements of urban political economy can be seen as the municipal government’s own organizational environment, which the government and its representatives must attend to in order to maintain their legitimacy, resource flows, and survival. Whether in pursuit of land tenure for community gardens or other public investments in quality of life, residents and community organizations inevitably bump up against large-scale structural constraints—no matter how much access and influence they have with local decision-makers—as they try to change local policy to meet their goals. In recent decades, American governments at all levels from local to national have been affected by the spread of neoliberal ideology, encouraging a turn toward A city’s civic conventions form an important piece of the organizational environment in which community gardening programs develop and define themselves. Yet what is possible for urban agriculture in any given city is also contingent upon its political-economic context. As urban political ecologists would describe it, ideas about appropriate uses for urban space combine with material flows and conditions, as well as ideas governing the legitimacy of governments themselves, in order to determine the actual production of urban socio-nature . In this regard, the distribution and character of urban agriculture in any city is influenced by local economic pressures, the sources and extent of public resources, and political factors at larger scales such as the laws and activities of state and federal governments. These elements of urban political economy can be seen as the municipal government’s own organizational environment, plant grow table which the government and its representatives must attend to in order to maintain their legitimacy, resource flows, and survival.

Whether in pursuit of land tenure for community gardens or other public investments in quality of life, residents and community organizations inevitably bump up against large-scale structural constraints—no matter how much access and influence they have with local decision-makers—as they try to change local policy to meet their goals. A primary set of structural constraints affecting all three cities is their existence in a market economy. In recent decades, American governments at all levels from local to national have been affected by the spread of neoliberal ideology, encouraging a turn toward privatization and new forms of commodification, reduction in taxes and public services, and government intervention to support market processes through deregulation and “entrepreneurial” initiatives . Local governments differ on many fronts, as reflected in the civic conventions they pay homage to, but in the US context they have all been forced into a fiscal squeeze by the reduction of federal funding, and they have confronted this challenge with the shared goal of increasing property values, the local population, and with them the overall prosperity of their local economy . All three case-cities are participants in a globalizing competition to attract capital and “win” at urban growth, and although they vary in their recent histories of “winning” and “losing” the competition for growth, all three cities show how urban growth machine logic and the political-economic pressures on municipalities influence the ways in which urban agriculture has been legitimized as a long-term land use. One common thread is the commodification of nature that runs concurrently with the commodification of land. In each of the case-cities, urban agriculture advocates have taken a different approach to building an economic argument that bolsters the legitimacy of urban agriculture as a land use.

The commonality—bolstering urban agriculture’s legitimacy with an economic rationale—reflects how pervasively market logic is applied to land use in American cities, while the differences between the cases demonstrate variations in how land is commodified based on the local growth coalition’s status in the competition for capital. By drawing attention to the ways that commodification of nature contributes to the production of uneven urban environments, urban political ecology enhances understanding of growth machine dynamics and their impact on the use value available to residents.In a similar vein, urban political ecologists employ the metaphor of urban metabolism to show how the constant reconfiguration of socio-natural space opens up opportunities for transforming relations of power. Addressing the tension between earlier Marxist and more recent actor-network theory approaches within the field of urban political ecology, Heynen highlights the “egalitarian potential that is embedded within a robust conceptualization of urban metabolism” . According to political ecologists, the tendency of nature to reproduce itself freely runs counter to the private property foundations of capitalism, and urban agriculture holds radical potential as an opportunity for people to produce and consume outside of the market, nourishing non-capitalist material flows . However, because the land on which urban agriculture occurs is commodified, I argue that this radical potential is limited in important ways. Urban growers and the spaces they cultivate do contribute to the creative dynamism of socio-natural circulation: they work to reshape the ecology of cities, sustain bodies left undernourished by the capitalist food system, and promote a wider reimagining of urban relations; however, these material and discursive metabolic flows are still subject to the gravity of capitalist property relations and the mutually reinforcing interests of urban growth coalition members.

Asserting the ongoing relevance of Marxist readings of urban political ecology, I show in this chapter how urban political economy serves as an inescapable force influencing land use policy and the decision-making of elected officials. As noted above, in all three cities I investigated, community garden organizations ultimately succeeded in legitimizing urban agriculture as a land use by building narratives that emphasize the potential economic benefits of growing food on vacant lots, a commonality which demonstrates just how strong urban growth and market logics are as governing principles in US cities. Yet there is more to learn from comparing the commodification of nature across the three cases. The economic rationales for urban agriculture developed along distinct trajectories that illustrate how variations in organizational legitimation strategies, local economic conditions, and state-level political contexts combine in the construction of different discursive frames and physical manifestations of urban nature. Comparatively, the local governments in Milwaukee and Philadelphia have faced more acute financial strain in recent decades than the City of Seattle. Milwaukee and Philadelphia have both struggled in the globalized competition for urban growth, while Seattle has largely succeeded. Compounding the effects of reduced federal funding, capital flight has limited the public resources available for social services and urban agriculture investment in both Milwaukee and Philadelphia. Many of the cascading challenges and social maladies are similar for all cities coping with capital flight, but Milwaukee and Philadelphia have diverged in how they construct the role of land in reversing the city’s fortune. In Milwaukee, land is a lifeline that needs to be reserved for potential property tax revenue, while in Philadelphia, land is a liability that has burdened the city budget and deterred development. In Seattle, where the local growth coalition has been winning in the competition to attract capital and the creative class, land has served as a selling point for the city’s livability. The City of Seattle currently has the most public resources available to invest in its community gardens—but upon close inspection, the benefits still accrue unevenly.In Milwaukee, civic conventions that support bottom-up governance facilitated the communication of resident desires regarding urban agriculture, hydroponic table including access to vacant lots and public resources to improve existing projects. As much as city officials are receptive to resident desires and cognizant of the multiple potential ways that urban agriculture works to meet these desires, the scale of poverty in Milwaukee—and legal limitations imposed by state laws—make it difficult for the municipal government to provide consistent financial support for community gardens and similar resident-led initiatives. Facing a severely constrained budget and compounding social problems caused by capital flight and economic decline, the City of Milwaukee is essentially caught doing triage as it attempts to address pressing social problems and attract new investment to regrow its tax base and the economy. Like many cities in the Midwest, Milwaukee has struggled to maintain its economic base with the decline of American manufacturing. In every decade since 1960, the city’s population has decreased, with the most precipitous contraction between 1970 and 1980 when the city lost 11% of its residents. It was during this time that in Milwaukee, as in many other American cities, community gardening received a surge of attention as a strategy to help residents feed themselves amid rising unemployment and higher food costs. Unemployment and poverty persist as major problems in Milwaukee today; the poverty rate is over 25%, and while the unemployment rate has moderately improved to a little under 7% in 2021, the rate for the city’s Black population is almost twice as high . With the decline of the manufacturing sector and inadequate access to transportation, many in Milwaukee—especially on the Near North Side, with the highest concentration of Black residents—cannot commute to what jobs are available .

High unemployment and concentrated poverty have brought on a host of problems including food insecurity, poor health outcomes, crime, and housing instability .Because urban agriculture has been legitimized as a land use and city leaders appreciate potential benefits that the gardens provide, officials have helped gardeners find funding where possible. In addition to the funding from CIP grants described in chapter 3, the Common Council has allocated over $600,000 for beautification and food access initiatives in recent years, some of which has been used to support community gardens. Given the city’s dire fiscal situation, such an amount of money that indicates the impact that urban agriculture organizations have made on the city’s priorities. Without the resources to provide more from the municipal budget, supportive city officials have partnered with other organizations in the region to leverage additional funding for Milwaukee’s community gardens and other green spaces. One source of funding is directly tied to the notion of urban agriculture as a source of employment. In partnership with the county’s federally funded workforce development office, Employ Milwaukee, the City of Milwaukee runs a summer youth employment program called Earn & Learn. Employ Milwaukee pays the wages for young people ages 14-24 who work for local government, nonprofit, and faith-based organizations and gain marketable skills in the process . Groundwork Milwaukee and some individual community gardens participate in Earn & Learn, employing youth to maintain gardens and other green spaces or to prepare and sell food from local urban farms. The organizations could not afford to pay the youth from their own budgets, but they are able to supervise them and provide job training that is considered a valuable workforce development experience by the county, the federal government, and the corporate and philanthropic donors that support Earn & Learn. As governments have reduced their own budgets and the scope of social service provision, the Earn & Learn program is typical of the kind of public-private partnerships that are expanding as the public sector becomes increasingly reliant on nonprofits to fulfill a public service. Furthermore, the fact that “workforce development” is considered a public service at all demonstrates the restructuring of relationships between the public, private and third sectors that has occurred through the influence of neoliberal ideology. With limited resources for the public services of food provision, urban beautification, and community programming, the City of Milwaukee seems to be doing what it can to support these areas as an ancillary benefit of the Earn & Learn workforce training, which is ultimately funded to benefit the private sector. The City of Milwaukee has found another financially motivated partner to support community gardens and other open space investments in the Milwaukee Metropolitan Sewer District . Like 850 other municipalities in the US, Milwaukee uses a combined sewer system which drains storm water along with sewage and industrial wastewater, creating the risk for sewer overflows during heavy rainfall that presents a “priority water pollution concern” for the federal government . Due to climate change, the Great Lakes region is facing an increased likelihood of heavy rainfall events—and therefore more frequent combined sewer overflows . Because of the potential for being fined by the Environmental Protection Agency when overflows occur, local water utilities with combined sewer systems, especially those in the Great Lakes region, have a serious financial interest in increasing their capacity for storm water management. Working in partnership with the City of Milwaukee, the MMSD and the Fund for Lake Michigan have invested billions of dollars to expand both “grey” and “green” infrastructure for storm water management—not only increasing the capacity of pipes and underground storage tanks, but also adding trees and bioswales and preserving open spaces so that more rainwater can be absorbed into the ground rather than flowing into the sewer system.

When civic conventions are built into the local governance infrastructure, such as the mandates of various agencies or the procedures for urban planning, these formalized conventions are an aspect of the local political opportunity structure. That is, civic conventions involve legal and institutional arrangements that can present openings for social movements to pursue particular policies or decisions . Civic conventions in the form of policy infrastructure create important leverage points for organizations to apply political pressure, while conventions in the form of ideas are important to movement formation and mobilization. Civic conventions are not uniform across the three cities I investigated, yet as this chapter will demonstrate, these features of the local context have played a role in shaping the nature of mobilization to support urban agriculture in all three cases. The political opportunity structure in Milwaukee supported efforts to legitimate gardens through insider strategies to craft and enact supportive policy, while the discursive opportunity structure seemed to suggest less need or opening for widespread mobilization. Philadelphia’s civic conventions created essentially the opposite opportunity structure, in which advocates have successfully organized to build pressure from the outside with narratives about the injustice and inefficiency of the city’s existing policies. In Seattle, both the discursive and political opportunity structures supported the gardeners’ efforts to preserve their sites; periods of both insider and outsider strategies have contributed to the robust, secure, seedling grow rack and thoroughly institutionalized network of gardens Seattle has today.The civic conventions in Milwaukee include a tradition of bottom-up governance that has translated from ideas to infrastructure over time.

As a result, urban agriculture organizations have enjoyed a political opportunity structure favorable to voicing their interests directly to city officials, securing policy improvements and some public resources for their projects, without having to depart from their legitimized role as community benefit organizations. However, as Chapter 4 will explain, public resources in Milwaukee are severely constrained, meaning the city government has ultimately been unable to invest much in garden development or preservation, no matter how legitimate they consider urban agriculture to be. Additionally, the local civic conventions foster an expectation of bottom-up engagement while assuming good governance overall; these civic conventions do not broadly extend to an expectation that citizens should engage in ongoing activism and social movement activities to pressure their government for accountability. In other words, the discursive opportunity structure is less favorable to mobilization in defense of threatened gardens. Overall, Milwaukee’s civic conventions have created opportunities for community-based organizations to use insider advocacy strategies through the existing infrastructure for bottom-up governance, without presenting as much opportunity for organizations to organize a robust social movement to pressure city officials for longer-term garden tenure or greater community control over land use. Historically, Milwaukee was the center of “sewer socialism,” a political movement organized around public investments in physical infrastructure. Between 1910 and 1960, the Socialist Party was highly successful in Milwaukee politics, winning public support in large part because of honest-government platforms and improvements that Socialist officials achieved in sanitation, water and energy systems, and community parks—including the preservation of the Milwaukee lakefront for perpetual public access .

Unlike Socialist Party politics elsewhere, Milwaukee’s Socialist movement was less ideological and more pragmatic. The civic conventions that developed in Milwaukee as a legacy of this era include ideas about good governance, but not as much identification with confrontational “usvs.-them” politics as may be expected for a city with a strong Socialist history. Nevertheless, an ethic of straightforward and transparent policy making in the interest of the general public has endured from the days of sewer socialism, contributing to the development of some bottom-up governance infrastructure. One notable element of the city’s governance infrastructure that serves to actualize resident ideas is the Community Improvement Projects program administered by the Neighborhood Improvement Development Corporation. Through this program, the city provides matching grants of up to $4,000 for resident-proposed projects that “stimulate resident engagement and support sustainable projects within a small geographic area” . Community gardens across the city have won these grants to support garden improvements, increasing the legitimacy of these sites because of the city’s endorsement and financial backing as represented by the CIP award. In recent years, particularly through its Department of Community Development, the City of Milwaukee has paid attention to residents’ ideas and priorities and has brought them into consideration in their urban planning. In 2012 and 2013, the Barrett administration conducted a survey and outreach meetings with residents to develop a sustainability plan for the city. One interviewee stressed that the prevalence of food in public opinion was unexpected: “when surveys have been taken over the years around Milwaukee, and there are issues around sustainability, I think the City people were shocked how much food came up” .

The ReFresh MKE Plan produced in 2013 showed that residents identified “empty lots and abandoned buildings” and “access to healthy food” as two of the city’s greatest sustainability challenges . Furthermore, “Fresh local food” was the single most common response given for “ideas that you think Milwaukee should focus on in its Sustainability Plan.” At the same time as ReFresh MKE was being drafted, the Department of Community Development was compiling a Vacant Lot Handbook with ideas for how residents could work with the city to repurpose unused land, based on examples of existing neighborhood projects that residents had initiated—including community gardens. As they developed these plans with attention to resident activities and priorities, city officials gained appreciation for the potential for urban agriculture to address important public needs. Thus, urban agriculture increased its legitimacy in the eyes of city officials as a tool to address public priorities developed from the bottom up. Adhering to civic conventions supporting governance in the public interest, Milwaukee city officials have been receptive to many proposals related to urban agriculture. The Common Council has approved land transfers to some formally organized community gardens located on unbuildable lots or in the city’s most economically depressed neighborhoods. When Will Allen, a local celebrity and nationally renowned director of Growing Power, sought to build a 5-story vertical farm and urban agriculture center, the city’s planners and Common Council worked with him to make necessary changes to the zoning code. The Common Council also approved a $250,000 forgivable loan for the expansion of Sweet Water Organics, an aquaponics business that hoped to scale up its operations and create more urban agriculture jobs. In 2012, in pursuit of a $5 million award in the Bloomberg Mayors Challenge, a competition to support innovative ideas for city improvement, the Barrett administration sketched out a proposal around addressing foreclosed properties while growing the local food system. When they made it to the semi-final round of the challenge, the administration set up a website to receive project ideas from Milwaukee residents, and then held a public forum to hear presentations for the top ten ideas. In all of these situations, greenhouse growing racks the city showed its interest in urban agriculture and openness to advocates’ proposals for new initiatives. Demonstrating the favorable political opportunity structure for garden advocates in Milwaukee, the city government has also been amenable to broader policy changes that facilitate urban agriculture. In 2010 the Common Council and city planners collaborated with the Milwaukee Food Council to revise the city’s zoning policy in a way that would permit urban agriculture in almost all parts of the city. With government officials so receptive to advocates’ input, the leaders of urban agriculture organizations my not have felt it necessary to mobilize the public around preserving community gardens, as doing so would potentially step outside the city’s civic conventions. While ideas about good governance are widely shared, they largely assume that the city officials will act in the public interest without needing constant vigilance and the pressure from grassroots mobilization and protest. Ideas about the value and need for active civic participation are not as widespread in Milwaukee as, for example, I found them to be in my investigation of Seattle. Over the history of the Milwaukee Urban Gardens / MKE Grows program, gardeners have been asked at a few moments to call or write to their Aldermen or to attend a particular public hearing. However, at no point did the program or other advocates in the city appear to sustain any outsider political strategies, as has occurred in both Seattle and Philadelphia.

Out of the three cities, Milwaukee interviews and archival materials demonstrated the least engagement with neighborhood associations or citizen advisory committees. In my qualitative analysis of in-depth interviews and community documents, codes for civic participation, citizen voice, organizing and mobilization, and political pressure or influence were also the least frequent in Milwaukee documents and interviews, while the code for assumed city support had its highest frequency in Milwaukee. As mentioned above, the city sold some land in its inventory to community gardening groups; this happened between 2013 and 2017, with very little public engagement. In the six Common Council meetings where these land sales were approved, the only people who showed up to speak were the purchasers themselves and Yves LaPierre, an official from the Department of Community Development’s real estate division who manages the city’s garden leases. Apparently, LaPierre’s presence alongside the purchasers served to confer adequate legitimacy on the transaction for it to win council approval. Additional supporters of the purchasing organization, community gardeners or other urban agriculture advocates did not participate in any of the hearings. Their absence aligns with the city’s civic conventions that suggest grassroots political pressure is not a normative aspect of the local public’s civic expectations or repertoire. Indeed, the city has acted favorably toward urban agriculture without much public pressure. With Will Allen forming personal relationships with Mayor Barrett and other city officials and bringing a national spotlight to Milwaukee as a place using urban agriculture to improve people’s lives, government support for urban agriculture appears to have been greater than for other types of resident-driven activity. The city’s multi-million-dollar HOME GR/OWN program demonstrates a belief in the potential of urban agriculture as a community investment. This “catalytic project,” designed to meet goals in the ReFresh MKE sustainability plan, leverages public funds, land and staffing along with private investments and philanthropic support specifically to repurpose vacant lots and help people grow food. In Milwaukee, the prestigious national awards that Will Allen has won for his innovations in urban agriculture have helped to bring urban agriculture additional legitimacy along with that accrued due to the city’s baseline receptivity to resident interests. City officials have come to appreciate how urban agriculture could be used to define the city, attract outside funding, and build the local economy. However, this appreciation has its limits. As Chapter 4 will illustrate, city officials are loath to remove potentially developable properties from the tax rolls by transferring ownership to a tax-exempt organization. Eight out of my 18 interviewees, both garden advocates and city officials, stated this as if it were a matter of fact. One garden program leader, recounting a time when they were previously told to move their garden from a city-owned lot, explained that the city was prioritizing a potential development over the garden “because the city of course is looking at their tax base. And being a nonprofit, whether we purchase the land or whether we’re leasing the land, the city’s not making any money that way” . Like other interviewees from Milwaukee, this program leader took for granted that the city’s primary interest in land use decisions is tax revenue. Widely recognizing the limits to the city’s appreciation for urban agriculture, garden advocates in Milwaukee have rarely mobilized to resist garden removal. Both before and after MUG was established, when particular gardens have faced development threats, the more common reaction has been a sense of inevitability. Thus, while government support for urban agriculture is often assumed in Milwaukee, the people involved in urban agriculture projects understand that support only extends so far. In line with the city’s civic conventions, advocates have used the political opportunity structures available to them, such as Community Improvement Projects funding and the Barrett administration’s receptivity to citizens’ ideas about urban agriculture, to advance pragmatic policies to improve residents’ lives through urban agriculture. However, Milwaukee’s discursive opportunity structure does not support more confrontational strategies or radical, redistributive demands.