Given the presence of amines in outdoor air that ventilates buildings, amines are also common constituents of indoor air, including airborne particles, and in indoor surface films. Indoor sources of amines, in addition to outdoor-to-indoor transport, include smoking; cooking; anticorrosive agents used in humidification or HVAC units; textiles and textile carpet tiles; and the decomposition of casein-containing building materials. Amines, amino acids, and urea are also known constituents of human skin.These compounds are used as active agents in personal care products, including skin moisturizers. Schmeltz and Hoffmann reviewed amines and amino acids identified in tobacco smoke.Their tabulations included 36 aliphatic amines with one to eight carbons, 40 aromatic amines including many aniline related species, and 16 amino acids. The 16 amino acids are noteworthy, given their relatively low volatility. α-Alanine is the most abundant amino acid. Grimmer et al. measured aromatic amines in mainstream and sidestream cigarette smoke.The identified amines included 2-aminobiphenyl, 1-aminonaphthalene, 2- aminonaphthalene, 4-aminobiphenyl, 2-aminofluorene, 1-aminoanthracene, 9- aminophenanthrene, 2-aminoanthracene, 3-aminofluoranthene, 1-aminopyrene. Per cigarette, sidestream smoke contained about ten times the summed mass of amines as in mainstream smoke. Dolara and co-workers, 406 using a sensitive mass spectrometry method, also measured amines from mainstream and sidestream cigarette smoke. The summed mass of aniline, 2- toluidine, 3-toluidine, 4-toluidine, 2-ethylaniline, 3-ethylaniline, 4-ethylaniline, 2,3- dimethylaniline, 2,4-dimethylaniline, 2,5-dimethylaniline, 2,6-dimethylaniline, 1- naphthylamine, 2-naphthylamine, 2-methyl-1-naphthylamine, 2-aminobiphenyl,3- aminobiphenyl and 4-aminobiphenyl in mainstream smoke was 0.2-1.3 µg/cigarette,indoor garden table while in sidestream smoke the summed mass was 20-30 µg/cigarette. They also measured these and other aromatic amines in homes with and without smoking .
Amines are anticipated to be emitted during the cooking of proteinaceous foods, especially meat. However, neither Rogge et al. nor Schauer et al. mention simple amines in their detailed studies of organic emissions from meat cooking. Certain heterocyclic aromatic amines are known carcinogens, and, consequently, several studies address their occurrence in cooked food products, especially meat, fish, and poultry. However, we have found no studies that have examined the emission of heterocyclic aromatic amines into air during cooking. Chiang et al. targeted aromatic amines in cooking oil fumes.They found that fumes from heated sunflower oil, vegetable oil and refined lard contained 2-naphthylamine and 4-aminobiphenyl.Amines are used as corrosion inhibitors in systems designed to humidify indoor air. Given their volatility, they can be present in the air of rooms that are humidified by such systems. They can also partition to indoor surfaces in the humidified rooms. Early indoor measurements were made by NIOSH investigators responding to employee complaints at a Cornell University museum in Ithaca, NY. At this site, diethylaminoethanol , also known as diethylethanolamine, was used as a corrosion inhibitor at the time of the investigation. Among 14 samples collected by Fannick et al., DEAE was detected in two, at concentrations of 40 and 50 µg/m3 . The investigators proposed that some of the complaints resulted from contact with surfaces onto which DEAE had sorbed. Volent and Baer review the Cornell museum case and other cases in which DEAE has been identified in the air of museums with humidification systems.They state that DEAE can react with acidic pollutants in museum environments to form hygroscopic salts that can accelerate metal corrosion. Edgerton et al. used a trace atmospheric gas analyzer to make continuous measurements of DEAE and cyclohexylamine in a typical steam-humidified room at the Battelle facility in Columbus, OH.At 42% RH, the concentration of DEAE and cyclohexylamine were 0.6 ppb and 0.7 ppb , respectively. At 61% RH, the concentrations were 2.4 ppb for DEAEand 0.8 ppb for cyclohexylamine.
During humidification, sorption to room surfaces was found to be a major sink for these amines, with reported rates of transfer to surfaces as follows: at 42% RH, 12 µg/s for DEAE and 8 µg/s for cyclohexylamine; at 61% RH, 14 µg/s for DEAE and 11 µg/s for cyclohexylamine. Given the volume of the room and an estimated surface area , the corresponding average deposition velocity for these amines to room surfaces would be ~ 16 m/h, a value that exceeds the likely mass-transport limit. When the humidification system was off, the amines decayed more slowly than would be the case for removal by air exchange, indicating that the amines were desorbing from room surfaces. Although numerous studies have examined the emission of amines from indoor sources, only a few have measured amines in indoor air. The Dolara group measured aromatic amines in outdoor and indoor air at offices and residences in the greater Florence region of Italy.Aniline and 2-toluidine were above the detection limit in all samples. Aniline ranged from 15 ng/m3 in outdoor air to 190 ng/m3 in a hairdresser’s shop with smokers, while 2-toluidine ranged from 2.5 ng/m3 in outdoor air to 17 ng/m3 in a recreation room with smokers. The concentrations of these species were elevated in the office of a nonsmoker adjacent to offices with smokers . Other amines whose average concentrations exceeded 2 ng/m3 in smoking environments included 3- and 4-toluidine and 2,3- 2,4- and 2,5-dimethylaniline. The Dolara group made more extensive measurements of aromatic amine concentrations in indoor and outdoor air in nine homes and 22 non-domestic buildings in Florence, Italy. Five of the homes were occupied by nonsmokers and four by smokers; the non-domestic sampling included both smoking and nonsmoking environments. Researchers focused on ten aromatic amines that they had measured in their earlier study: aniline, the three toluidine isomers , four dimethylaniline isomers , 2-naphtylamine and 4- aminobiphenyl. Excluding aniline, the summed indoor concentrations of nine of these amines were 5-11 ng/m3 in homes with nonsmokers and 15-34 ng/m3 in homes with smokers.
In the non-domestic buildings, summed indoor concentrations of these nine amines were < 20 ng/m3 in environments without smokers and tended to be higher with smoking. Aniline concentrations were commonly larger than the sum of the other nine amines and did not correlate with the concentrations of these other amines. Several of the non-domestic settings had aniline levels > 400 ng/m3 , including a hospital ward and a hospital waiting room. It was apparent that there were indoor aniline sources other than tobacco smoke. Zhu and Aikawa targeted nicotine and seven monoaromatic amines, including aniline, in measurements made in 69 residences in two regions of Canada. Smoking occurred in seven of these homes. Of the targeted compounds, only nicotine and aniline were routinely measured at levels above their detection limits. N-Methylaniline was detected in one home at 23 ng/m3 and was otherwise below its detection limit of 6 ng/m3 . N,N-Dimethylaniline, 2-ethylaniline, and 2- chloroaniline had detection limits of 9-10 ng/m3, while 4-ethylaniline and 2,4-dichloroaniline had detection limits of 20 ng/m3 . None of these amines were detected in any of the homes. Aniline was detected in 26 of the 69 homes, including five of the seven homes with smoking, at concentrations above the detection limit of 7 ng/m3. The highest aniline concentration in a home without smoking was 35 ng/m3 , while the highest level in a home with smoking was 58 ng/m3 . Among the homes in which aniline was successfully measured, without smoking, the mean concentrations in outdoor and indoor air were equal at 11 ng/m3 . The mean aniline concentration was higher in homes with smoking, 34 ng/m3 . In one of the homes, shoe polishing was demonstrated to contribute to indoor aniline concentrations. Akyüz developed an analytical method for measuring amines in air samples and demonstrated the method’s applicability for indoor and outdoor sampling during summer and winter months at six locations in Turkey.The indoor sites included both smoking and nonsmoking areas. In smoking environments,grow rack piperazine was measured at mean concentrations of 8 ng/m3 in summer and 22 ng/m3 in winter. In nonsmoking settings, average concentrations were 5 ng/m3 in summer and 10 ng/m3 in winter. Corresponding averages for aniline were 6 ng/m3 and 21 ng/m3 in smoking environments versus 1 ng/m3 and 4 ng/m3 in nonsmoking environments. Summed across 33 reported species , the mean concentrations for summer sampling were 42 ng/m3 in smoking environments, 20 ng/m3 in nonsmoking environments, and 13 ng/m3 outdoors.
For winter sampling, analogous results were 117 ng/m3 for smoking environments, 47 ng/m3 for nonsmoking environments, and 35 ng/m3 outdoors. Based on this small set of studies, we conclude that amines are commonly much more abundant in smoking than nonsmoking locations. In smoking environments, aniline, methylaniline isomers, butylamine, and piperazine dominate, while in the nonsmoking environments, aniline and the alkylamines dominate. Aniline is typically the most abundant amine indoors. The other amines are substantially less abundant. Amines and amino acids that have been measured or are anticipated to occur indoors are listed with some of their key properties in Tables 25 and 26, respectively.Given the reported presence of amino acids in outdoor airborne particles collected at both marine and land-based locations, 385 coupled with outdoor-to-indoor transport of such particles, one can anticipate that amino acids are present in particles indoors. Amino acids are present in sweat; in corneocytes; in skin surface films; and in natural moisturizing factor , which plays an important role keeping the stratum corneum hydrated. Hence, we expect these amino acids to be transferred to surfaces that humans contact, and to surfaces soiled with their squames . However, we found no peer-reviewed publications that report measurements of amino acids in either indoor airborne particles or indoor surface films.Dunstan et al. have reported amino acid levels in sweat collected from male athletes exercising at 32-34 °C. When the subjects began sweating, the net concentration of amino acids in their sweat was almost 10 mM. After 35-40 minutes of exercise, the net concentration in sweat had declined to match the net concentration of amino acids in plasma . That is, the sweat was no longer leaching amino acids from the stratum corneum. This abundance is presumably the lower bound for net amino acid concentration in sweat . In post-exercise sweat, the most abundant amino acids were histidine , serine , ornithine , glycine , and alanine ; total amino acid abundance was 8 mM. How significant are amino acids in sweat for potential accumulation on indoor surfaces? If an occupant transfers 10 ml of sweat to indoor surfaces , then ´ 10-4 moles of total amino acids would also be transferred. If the average molecular weight of the transferred amino acids is 100 g/mol, this equates to 3-10 mg of amino acids being transferred to indoor surfaces — equivalent to the whole-body emissions of ammonia over a period of 1-2 h approximately 5-10 h. The mass of amino acids transferred to clothing is expected to be substantially larger. Amines are the most abundant organic bases in outdoor air. Through acid-base reactions with sulfuric acid, they play key roles in atmospheric nucleation and particle formation. More generally, they can neutralize strong acids in outdoor air. For example, Shen et al. found that amines, emitted during the burning of coal in the Yangtze River Delta region of China, react with nitric and sulfuric acid to form aminium salts . Aminium nitrates were more abundant than aminium sulfates, with average concentrations of methylaminium, dimethylaminium and ethylaminium salts in aerosol particles of 6 ± 3 ng m−3 , 8 ± 5 ng m−3 , and 20 ± 17 ng m−3 , respectively. However, ammonium nitrate and ammonium sulfate tended to be 1000 to 10,000 times more abundant than these aminium salts, indicating the much more important role of ammonia as an atmospheric base. Reviews from the Wexler group discuss amine acid-base chemistry, and much of their discussion is applicable to indoor environments.Ge et al. specifically addresses chemical properties of amines, including Henry’s law constants, acid dissociation constants, vapor pressures, activity coefficients, solubilities, and solid/gas dissociation constants of their aminium salts. Amines contribute to new particle formation, including sulfuric acid nucleation.Reactions with strong acids such as HNO3, HCl and H2SO4 form aminium salts. Reactions with dicarboxylic acids form amides. Amines can also partition from the gas-phase to airborne particles. To have an impact on particle formation in outdoor or indoor environments, an amine must compete with ammonia for strong acids. Typically, outdoor ammonia concentrations are three orders of magnitude larger than outdoor amine concentrations, and indoor ammonia concentrations are even larger than those outdoors.