While household vacuum-cleaner dust represents contamination in several rooms over periods of months or years, interviewer collected dust provides information about contamination that is specific to a given room at a particular time. Two studies found that PBDEs measured in matched samples of interviewer-collected dust and household vacuum cleaner dust were moderately correlated and that household vacuum dust had significantly lower concentrations of PBDEs than interviewer-collected dust. Yet, other investigators have shown that levels of PAHs and PCBs in 40 matched samples of HVS3-sampled and household vacuum cleaner dusts were correlated and that median concentrations from both dust collection methods were similar . Differences in chemical concentrations measured in dust from the two collection methods are likely to be greatest when indoor chemical sources vary from room-to-room within a residence. There is some evidence that a subject’s biological levels of indoor contaminants may be more closely correlated to chemical concentrations measured in dust taken from their household vacuum cleaners than in dust collected from elevated surfaces in their living room . Once residential dust has been collected, it is generally sieved with cut points ranging from 150 µm to 2 mm. Subsequently, the fine dust is extracted with an organic solvent; the extract is chromatographically purified; and specific analytes are detected, typically by gas chromatography-mass spectrometry . This chapter will review global patterns in dust levels of PBDEs, PCBs, PAHs, and nicotine, identify known determinants of these dust levels, and estimate the relative contributions of dust contamination to human intake of these chemicals. This chapter will focus on studies that measured chemicals in residential-dust samples and omit reports of dust concentrations measured in schools, daycare centers, offices, public buildings, automobiles, etc., or in other media,how to dry cannabis such as soils or sediments. Polybrominated diphenyl ethers have been used worldwide as chemical flame retardants to treat textiles and plastics in consumer goods .
Three commercial PBDE mixtures; Penta-BDE, Octa-BDE, and Deca-BDE, have been manufactured. Each mix is comprised of several BDE congeners, but Penta-BDE is predominantly comprised of BDE-47 and BDE-99; Octa-BDE is predominantly comprised of BDE-183, BDE-196, and BDE-197; and Deca-BDE is predominantly comprised of BDE-209 . The European Union banned the use of Penta-BDE and Octa-BDE in 2004 and banned the use of Deca-BDE in 2008 due to concerns for public health. Similarly, PBDE producers in the U.S. phased out production and use of Penta-BDE and OctaBDE in 2004; however, Deca-BDE is still being used in the U.S. . To date, there is no legislation to limit the production or use of PBDEs in Asia . Despite the recent regulation of PBDEs in some countries, these chemicals are likely to persist in the indoor environment due to the ubiquitous presence of PBDE-treated consumer goods which can reside in homes for decades. Globally, PBDE consumption has varied by the quantities and mixtures of PBDEs used. Table 1 shows the regional consumption for three commercial PBDE mixtures reported in 2001 . In 2001, consumption of Penta-BDE, Octa-BDE, and Deca-BDE in the Americas exceeded that of Europe by 47-fold, 2-fold, and 3-fold, respectively. In comparisons between the Americas and Asia, the Americas consumed 47-fold more Penta-BDE but consumed comparable quantities of Octa-BDE and Deca-BDE. Although there is no readily available information regarding the use of PBDEs by country or state, there has likely been substantial regional variation. For example, the U.K. and California have stringent flammability standards that indirectly promote the use of Deca-DBE and Penta-BDE. Several investigators observed that biological PBDE levels in various populations mirror the global patterns in PBDE dust concentrations . Indeed, it is likely that the relatively high levels of PBDEs measured in blood and breast milk from North Americans compared to Europeans are the result of higher dust concentrations of PBDEs in North American residences . Researchers have also measured PBDEs in matched samples of dust and biological material and reported positive associations between subjects’ residential-dust PBDE levels and their corresponding biological levels.
Such associations were observed in geographical regions with both low and high levels of PBDE in dust. In the U.S., concentrations of PBDEs in residential dust were positively correlated with matched levels of PBDEs in serum and breast milk , as well as with various reproductive hormone levels in serum . Likewise, two studies from Europe observed significant relationships between PBDE levels in dust and plasma and one study from Sweden observed an association between PBDE levels in dust and breast milk . In contrast, two studies from the U.S. , two from Europe , and one from Australia were unable to detect positive associations between PBDEs measured in dust and matched biological samples. Two of these studies had only 10 subjects , three did not measure or could not detect BDE-209 in serum, and two observed that dust was a minor contributor to overall PBDE intake . The positive associations observed between PBDE levels in dust and biological samples suggest that dust is an important source of PBDE exposure worldwide. The estimated intake of PBDEs attributed to residential-dust exposure has varied widely within and between regions, but estimates from North America and Asia are generally higher than estimates from Europe .Two studies from Belgium and one from Germany suggest that residential-dust ingestion was likely responsible for less than 3% of overall PBDE exposure in European adults. In contrast, two studies from Canada estimated that dust ingestion contributed 14 and 65% of the total PBDE intake for adults, while two U.S. studies estimated that dust exposure contributed 56 and 82% of adult intake , and an Asian study estimated dust ingestion contributed 79% of adult intake. Based on these estimates, residential dust is expected to be the most important source of PBDE exposure for adults in geographical regions with relatively high PBDE dust levels . Moreover, children worldwide receive an even larger proportion of their total PBDE intake via dust ingestion compared to their adult counterparts due to hand-to-mouth behavior .
In summary, the available literature indicates that residential dust is an important contributor to PBDE intake in regions with heavy use of PBDEs. This suggests that levels of PBDEs in residential dust can be useful surrogates of total PBDE exposures in epidemiological studies.PBDEs have been incorporated into a myriad of household goods, including televisions, computers, and various other electric appliances as well as drapes, carpet, and furniture containing foam . PBDEs can be transferred from household items to indoor dust either as miniature fragments of foam or textiles via abrasion and weathering or following vaporization of PBDEs from hot surfaces in electronics with subsequent adsorption on dust particles . Few studies have successfully detected significant associations between levels of PBDEs in residential dust and the number of potentially PBDE-treated items in residences. In fact, of 14 studies that inventoried the number of foam-containing pieces of furniture, the number of electronic devices, and/or the typical use of electronic devices in study residences , only Suzuki et al. reported significant associations between these covariates and PBDE levels in dust. These authors reported significant correlations between total electrical appliance usage and dust concentrations of BDEs across 19 residences and 3 office buildings . One possible explanation for the paucity of positive associations is the wide range of bromination levels in similar consumer products . Allen et al. used X-ray fluorescence to identify bromine-containing household goods and illustrated that by excluding furniture without bromine from counts of PBDE-treated items, it was possible to measure a positive association between the number of electronic items and Deca-BDE congeners as well as between the number of foam containing furniture items and Penta-BDE congeners. Authors have examined other household characteristics ,best way to dry cannabis but have identified few determinants of PBDE dust levels . Stapleton et al. found a significant negative correlation between the residence square footage and the contribution of BDE-209 to the total PBDE dust concentrations. Similarly, de Wit et al. reported that median dust concentrations of BDE-209 were higher in apartments than in houses. In addition, Zota et al. found that dust collected from residences in a low-income community in California had higher PBDE levels than dust collected from residences in a more affluent California community. Because of their non-flammability and electrical insulation properties, polychlorinated biphenyls were used as coolants and lubricants in transformers, capacitors, and other electrical equipment and in a host of consumer products, including fluorescent lights, televisions, and refrigerators .
Due to concerns for human health, PCB production and use were restricted by various international regulations beginning in the 1970s . Still, because of the widespread use of PCBs, their persistence in the environment, and their bio-accumulation through the food chain, these chemicals are still ubiquitous in residences around the world. Three estimates of global PCB manufacture indicate that cumulative world-wide PCB production topped 1 million metric tons in 1980 and reached somewhere between 1.3 – 1.5 million metric tons by the time PCBs were entirely phased out of production in 1993 . Historically, the countries that have manufactured the most PCBs are the U.S., Russia, Germany, France, the U.K., and Japan, which produced 642, 174, 159, 135, 67, and 59 thousand metric tons of PCBs, respectively, by 1993 . Likewise, many of these nations were also major consumers of PCBs; with the U.S. consuming the largest portion of the world’s PCBs, followed by Russia , Germany , Japan , and France . The worldwide restriction of PCB production was implemented at different times in various countries. In 1973, member countries of the Organization for Economic Cooperation and Development , restricted production of PCBs to certain applications . Japan and the U.K. banned production of PCBs in 1972 and 1978, respectively, and in 1976, the U.S. congress passed the Toxic Substances Control Act, which phased out all U.S. production of PCBs by 1979 . In the 1980s, limited PCB production continued in Germany and France ; but a more stringent OECD decision in 1987 led to the cessation of all production, import, export, or sale of PCBs from these countries as well . Russia was the last major producer to phase-out PCB production . Recently, investigators have reported high concentrations of PCBs in dust associated with certain construction materials, such as caulking and wood floor finish , as well as with a PCB-contaminated fluorescent light ballast and a PCB-contaminated carpet pad . The prevalence of these particular PCB sources in residences is unknown; however, they are unlikely to be relevant in most homes. Ratios of indoor to outdoor PCB concentrations suggest that indoor PCB sources contribute substantially to PCB dust levels ; yet, investigators have had little success identifying demographics, household characteristics, or typical household items that have an impact on PCB dust concentrations . Two studies from the U.S. have found evidence that dust from older homes or older floors is more likely to contain high levels of PCBs . Colt et al. reported that, in multi-variable linear regression models, the age of the residence was associated with total PCB dust concentrations , with the highest levels found in residences built before 1960 and the lowest in residences built after 1980. Similarly, in the largest analysis of PCB determinants, Lee et al. reported that PCB concentrations were significantly associated with floor age in dust from 764 Michigan residences. Additionally, Lee et al. identified several factors that were associated with increased concentrations of PCBs in dust, including the presence of high-pile carpet, the presence of a vegetable or flower gardens, and elevated PCB concentrations in outdoor soil. In contrast, having a dog at the residence and increased dust loading , were associated with decreased concentrations of PCBs . Still, even the most comprehensive multi-variable model only explained 37% of the variability of PCB concentrations in residential dust . Polycyclic aromatic hydrocarbons are molecules with two or more fused aromatic rings that are formed as products of incomplete combustion. Humans are exposed to PAHs from a variety of indoor sources including cigarette smoke, wood burning fireplaces, gas appliances, and charred foods, as well as to outdoor sources, including vehicle exhaust and treatment of pavement with coal-tar-based sealants . Seven PAHs that have been classified by the U.S.