Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity.

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.

Chemistry, lung toxicity and mutagenicity of burn pit smoke-related particulate matter.

BACKGROUND: Open burning of anthropogenic sources can release hazardous emissions and has been associated with increased prevalence of cardiopulmonary health outcomes. Exposure to smoke emitted from burn pits in military bases has been linked with respiratory illness among military and civilian personnel returning from war zones. Although the composition of the materials being burned is well studied, the resulting chemistry and potential toxicity of the emissions are not. METHODS: Smoke emission condensates from either flaming or smoldering combustion of five different types of burn pit-related waste: cardboard; plywood; plastic; mixture; and mixture/diesel, were obtained from a laboratory-scale furnace coupled to a multistage cryotrap system. The primary emissions and smoke condensates were analyzed for a standardized suite of chemical species, and the condensates were studied for pulmonary toxicity in female CD-1 mice and mutagenic activity in Salmonella (Ames) mutagenicity assay using the frameshift strain TA98 and the base-substitution strain TA100 with and without metabolic activation (S9 from rat liver). RESULTS: Most of the particles in the smoke emitted from flaming and smoldering combustion were less than 2.5 µm in diameter. Burning of plastic containing wastes (plastic, mixture, or mixture/diesel) emitted larger amounts of particulate matter (PM) compared to other types of waste. On an equal mass basis, the smoke PM from flaming combustion of plastic containing wastes caused more inflammation and lung injury and was more mutagenic than other samples, and the biological responses were associated with elevated polycyclic aromatic hydrocarbon levels. CONCLUSIONS: This study suggests that adverse health effects of burn pit smoke exposure vary depending on waste type and combustion temperature; however, burning plastic at high temperature was the most significant contributor to the toxicity outcomes. These findings will provide a better understanding of the complex chemical and combustion temperature factors that determine toxicity of burn pit smoke and its potential health risks at military bases.

Urinary mutagenicity and oxidative status of wildland firefighters working at prescribed burns in a Midwestern US forest.

OBJECTIVE: Wildland firefighters (WLFFs) experience repeated exposures to wildland fire smoke (WFS). However, studies about WLFFs remain regionally limited. The objective of this study was to assess the effect of WFS exposure on urinary mutagenicity and cell oxidation among WLFFs who work at prescribed burns in the Midwestern USA. METHODS: A total of 120 spot urine samples was collected from 19 firefighters right before (pre-shift), immediately after (post-shift), and the morning (next-morning) following work shifts on prescribed burn days (burn days) and regular workdays (non-burn days). The levels of urinary mutagenicity, 8-isoprostane, malondialdehyde and oxidised guanine species (Ox-GS) were measured. Linear mixed-effect models were used to determine the difference of cross-shift changes in the concentrations of urinary biomarkers. RESULTS: Post-shift levels of creatinine-corrected urinary mutagenicity and 8-isoprostane were non-significantly higher than pre-shift levels (1.16× and 1.64×; p=0.09 and 0.07) on burn days. Creatinine-corrected Ox-GS levels increased significantly in next-morning samples following WFS exposure (1.62×, p=0.03). A significant difference in cross-shift changes between burn and non-burn days was observed in 8-isoprostane (2.64×, p=0.03) and Ox-GS (3.00×, p=0.02). WLFFs who contained the fire (performed holding tasks) had a higher pre-morning to next-morning change in urinary mutagenicity compared with those who were lighting fires during the prescribed burns (1.56×, p=0.03). CONCLUSIONS: Compared with the other regions, WLFFs who worked in Midwestern forests had an elevated urinary mutagenicity and systemic oxidative changes associated with WFS exposure at prescribed burns.

Predictive Analysis Using Chemical-Gene Interaction Networks Consistent with Observed Endocrine Activity and Mutagenicity of U.S. Streams.

In a recent U.S. Geological Survey/U.S. Environmental Protection Agency study assessing more than 700 organic compounds in 38 streams, in vitro assays indicated generally low estrogen, androgen, and glucocorticoid receptor activities, with 13 surface waters with 17ß-estradiol-equivalent (E2Eq) activities greater than a 1-ng/L estimated effects-based trigger value for estrogenic effects in male fish. Among the 36 samples assayed for mutagenicity in the Salmonella bioassay (reported here), 25% had low mutagenic activity and 75% were not mutagenic. Endocrine and mutagenic activities of the water samples were well correlated with each other and with the total number and cumulative concentrations of detected chemical contaminants. To test the predictive utility of knowledge-base-leveraging approaches, site-specific predicted chemical-gene (pCGA) and predicted analogous pathway-linked (pPLA) association networks identified in the Comparative Toxicogenomics Database were compared with observed endocrine/mutagenic bioactivities. We evaluated pCGA/pPLA patterns among sites by cluster analysis and principal component analysis and grouped the pPLA into broad mode-of-action classes. Measured E2eq and mutagenic activities correlated well with predicted pathways. The pPLA analysis also revealed correlations with signaling, metabolic, and regulatory groups, suggesting that other effects pathways may be associated with chemical contaminants in these waters and indicating the need for broader bioassay coverage to assess potential adverse impacts.

Urinary mutagenicity and other biomarkers of occupational smoke exposure of wildland firefighters and oxidative stress.

Background: Wildland firefighters conducting prescribed burns are exposed to a complex mixture of pollutants, requiring an integrated measure of exposure. Objective: We used urinary mutagenicity to assess if systemic exposure to mutagens is higher in firefighters after working at prescribed burns versus after non-burn work days. Other biomarkers of exposure and oxidative stress markers were also measured. Methods: Using a repeated measures study design, we collected urine before, immediately after, and the morning after a work shift on prescribed burn and non-burn work days from 12 healthy subjects, and analyzed for malondialdehyde (MDA), 8-isoprostane, 1-hydroxypyrene (OH-pyrene), and mutagenicity in Salmonella YG1041 +S9. Particulate matter (PM2.5) and carbon monoxide (CO) were measured by personal monitoring. Light-absorbing carbon (LAC) of PM2.5 was measured as a surrogate for black carbon exposure. Linear mixed-effect models were used to assess cross-work shift changes in urinary biomarkers. Results: No significant differences occurred in creatinine-adjusted urinary mutagenicity across the work shift between burn days and non-burn days. Firefighters lighting fires had a non-significant, 1.6-fold increase in urinary mutagenicity for burn versus non-burn day exposures. Positive associations were found between cross-work shift changes in creatinine-adjusted urinary mutagenicity and MDA (p = 0.0010), OH-pyrene (p = 0.0001), and mass absorption efficiency which is the LAC/PM2.5 ratio (p = 0.2245), respectively. No significant effect of day type or work task on cross-work shift changes in MDA or 8-isoprostane was observed. Conclusion: Urinary mutagenicity may serve as a suitable measure of occupational smoke exposures among wildland firefighters, especially among those lighting fires for prescribed burns.

Chlorination of Source Water Containing Iodinated X-ray Contrast Media: Mutagenicity and Identification of New Iodinated Disinfection Byproducts.

Iodinated contrast media (ICM) are nonmutagenic agents administered for X-ray imaging of soft tissues. ICM can reach µg/L levels in surface waters because they are administered in high doses, excreted largely unmetabolized, and poorly removed by wastewater treatment. Iodinated disinfection byproducts (I-DBPs) are highly genotoxic and have been reported in disinfected waters containing ICM. We assessed the mutagenicity in Salmonella of extracts of chlorinated source water containing one of four ICM (iopamidol, iopromide, iohexol, and diatrizoate). We quantified 21 regulated and nonregulated DBPs and 11 target I-DBPs and conducted a nontarget, comprehensive broad-screen identification of I-DBPs. We detected one new iodomethane (trichloroiodomethane), three new iodoacids (dichloroiodoacetic acid, chlorodiiodoacetic acid, bromochloroiodoacetic acid), and two new nitrogenous I-DBPs (iodoacetonitrile and chloroiodoacetonitrile). Their formation depended on the presence of iopamidol as the iodine source; identities were confirmed with authentic standards when available. This is the first identification in simulated drinking water of chloroiodoacetonitrile and iodoacetonitrile, the latter of which is highly cytotoxic and genotoxic in mammalian cells. Iopamidol (5 µM) altered the concentrations and relative distribution of several DBP classes, increasing total haloacetonitriles by >10-fold. Chlorination of ICM-containing source water increased I-DBP concentrations but not mutagenicity, indicating that such I-DBPs were either not mutagenic or at concentrations too low to affect mutagenicity.

Photochemical Conversion of Surrogate Emissions for Use in Toxicological Studies: Role of Particulate- and Gas-Phase Products.

The production of photochemical atmospheres under controlled conditions in an irradiation chamber permits the manipulation of parameters that influence the resulting air-pollutant chemistry and potential biological effects. To date, no studies have examined how contrasting atmospheres with a similar Air Quality Health Index (AQHI), but with differing ratios of criteria air pollutants, might differentially affect health end points. Here, we produced two atmospheres with similar AQHIs based on the final concentrations of ozone, nitrogen dioxide, and particulate matter (PM2.5). One simulated atmosphere (SA-PM) generated from irradiation of ∼23 ppmC gasoline, 5 ppmC α-pinene, 529 ppb NO, and 3 µg m-3 (NH4)2SO4 as a seed resulted in an average of 976 µg m-3 PM2.5, 326 ppb NO2, and 141 ppb O3 (AQHI 97.7). The other atmosphere (SA-O3) generated from 8 ppmC gasoline, 5 ppmC isoprene, 874 ppb NO, and 2 µg m-3 (NH4)2SO4 resulted in an average of 55 µg m-3 PM2.5, 643 ppb NO2, and 430 ppb O3 (AQHI of 99.8). Chemical speciation by gas chromatography showed that photo-oxidation degraded the organic precursors and promoted the de novo formation of secondary reaction products such as formaldehyde and acrolein. Further work in accompanying papers describe toxicological outcomes from the two distinct photochemical atmospheres.

Evaluation of an Air Quality Health Index for Predicting the Mutagenicity of Simulated Atmospheres.

No study has evaluated the mutagenicity of atmospheres with a calculated air quality health index (AQHI). Thus, we generated in a UV-light-containing reaction chamber two simulated atmospheres (SAs) with similar AQHIs but different proportions of criteria pollutants and evaluated them for mutagenicity in three Salmonella strains at the air-agar interface. We continuously injected into the chamber gasoline, nitric oxide, and ammonium sulfate, as well as either α-pinene to produce SA-PM, which had a high concentration of particulate matter (PM): 119 ppb ozone (O3), 321 ppb NO2, and 1007 µg/m3 PM2.5; or isoprene to produce SA-O3, which had a high ozone (O3) concentration: 415 ppb O3, 633 ppb NO2, and 55 µg/m3 PM2.5. Neither PM2.5 extracts, NO2, or O3 alone, nor nonphoto-oxidized mixtures were mutagenic or cytotoxic. Both photo-oxidized atmospheres were largely direct-acting base-substitution mutagens with similar mutagenic potencies in TA100 and TA104. The mutagenic potencies [(revertants/h)/(mgC/m3)] of SA-PM (4.3 ± 0.4) and SA-O3 (9.5 ± 1.3) in TA100 were significantly different ( P < 0.0001), but the mutation spectra were not ( P = 0.16), being ∼54% C → T and ∼46% C → A. Thus, the AQHI may have some predictive value for the mutagenicity of the gas phase of air.

Mutagenic atmospheres resulting from the photooxidation of aromatic hydrocarbon and NOx mixtures.

Although many volatile organic compounds (VOCs) are regulated to limit air pollution and the consequent health effects, the photooxidation products generally are not. Thus, we examined the mutagenicity in Salmonella TA100 of photochemical atmospheres generated in a steady-state atmospheric simulation chamber by irradiating mixtures of single aromatic VOCs, NOx, and ammonium sulfate seed aerosol in air. The 10 VOCs examined were benzene; toluene; ethylbenzene; o-, m-, and p-xylene; 1,2,4- and 1,3,5-trimethylbenzene; m-cresol; and naphthalene. Salmonella were exposed at the air-agar interface to the generated atmospheres for 1, 2, 4, 8, or 16 h. Dark-control exposures produced non-mutagenic atmospheres, illustrating that the gas-phase precursor VOCs were not mutagenic at the concentrations tested. Under irradiation, all but m-cresol and naphthalene produced mutagenic atmospheres, with potencies ranging from 2.0 (p-xylene) to 10.4 (ethylbenzene) revertants m3 mgC-1 h-1. The mutagenicity was due exclusively to direct-acting late-generation products of the photooxidation reactions. Gas-phase chemical analysis showed that a number of oxidized organic chemical species enhanced during the irradiated exposure experiments correlated (r ≥ 0.81) with the mutagenic potencies of the atmospheres. Molecular formulas assigned to these species indicated that they likely contained peroxy acid, aldehyde, alcohol, and other functionalities.

Progressive Increase in Disinfection Byproducts and Mutagenicity from Source to Tap to Swimming Pool and Spa Water: Impact of Human Inputs.

Pools and spas are enjoyed throughout the world for exercise and relaxation. However, there are no previous studies on mutagenicity of disinfected spa (hot tub) waters or comprehensive identification of disinfection byproducts (DBPs) formed in spas. Using 28 water samples from seven sites, we report the first integrated mutagenicity and comprehensive analytical chemistry of spas treated with chlorine, bromine, or ozone, along with pools treated with these same disinfectants. Gas chromatography (GC) with high-resolution mass spectrometry, membrane-introduction mass spectrometry, and GC-electron capture detection were used to comprehensively identify and quantify DBPs and other contaminants. Mutagenicity was assessed by the Salmonella mutagenicity assay. More than 100 DBPs were identified, including a new class of DBPs, bromoimidazoles. Organic extracts of brominated pool/spa waters were 1.8× more mutagenic than chlorinated ones; spa waters were 1.7× more mutagenic than pools. Pool and spa samples were 2.4 and 4.1× more mutagenic, respectively, than corresponding tap waters. The concentration of the sum of 21 DBPs measured quantitatively increased from finished to tap to pool to spa; and mutagenic potency increased from finished/tap to pools to spas. Mutagenic potencies of samples from a chlorinated site correlated best with brominated haloacetic acid concentrations (Br-HAAs) (r = 0.98) and nitrogen-containing DBPs (N-DBPs) (r = 0.97) and the least with Br-trihalomethanes (r = 0.29) and Br-N-DBPs (r = 0.04). The mutagenic potencies of samples from a brominated site correlated best (r = 0.82) with the concentrations of the nine HAAs, Br-HAAs, and Br-DBPs. Human use increased significantly the DBP concentrations and mutagenic potencies for most pools and spas. These data provide evidence that human precursors can increase mutagenic potencies of pools and spas and that this increase is associated with increased DBP concentrations.

DNA adducts induced by in vitro activation of extracts of diesel and biodiesel exhaust particles.

CONTEXT: Biodiesel and biodiesel-blend fuels offer a renewable alternative to petroleum diesel, but few data are available concerning the carcinogenic potential of biodiesel exhausts. OBJECTIVES: We compared the formation of covalent DNA adducts by the in vitro metabolic activation of organic extracts of diesel-exhaust particles (DEP) from petroleum diesel and soy biodiesel and correlated DNA adduct levels and mutagenicity in Salmonella TA100. METHODS: We examined two different DEP from petroleum diesel (C-DEP and B0), one from soy bean oil biodiesel (B100) and one from combustion of a blend of 20% B100 and 80% B0 (B20) for in vitro DNA adduct-forming potential under oxidative or nitroreductive conditions in the presence of calf thymus DNA as well as in vivo in Salmonella TA100. The modified DNA was hydrolyzed and analyzed by (32)P-postlabeling using either butanol extraction or nuclease P1 pre-enrichment. RESULTS: Multiple DNA adducts were produced with chromatographic mobilities consistent with PAH and nitro-PAH adducts. The types and quantities of DNA adducts produced by the two independent petroleum diesel DEP were similar, with both polycyclic aromatic hydrocarbon (PAH)- and nitro-PAH-derived adducts formed. Relative potencies for S9-mediated DNA adduct formation, either per mass of particulate or per MJ(th) energy consumed were B100 > B0 > B20. CONCLUSIONS: Soy biodiesel emissions induced DNA damage in the form of presumptive PAH and nitro-PAH DNA adducts that correlated with mutagenicity in Salmonella. B20 is the soy biodiesel used most commonly in the US, and it produced the lowest DNA adduct-emission factor, ∼50% that of petroleum diesel.

Health effects of soy-biodiesel emissions: bioassay-directed fractionation for mutagenicity.

CONTEXT: Soy biodiesel is the predominant biodiesel in the USA, but there is little understanding of the classes of chemicals responsible for the mutagenicity of its emissions. OBJECTIVE: We determined some of the chemical classes responsible for the mutagenicity of the particulate matter (PM) of the emissions from petroleum diesel (B0) and biodiesel containing increasing concentrations of soy methyl esters (B20, B50, and B100). MATERIALS AND METHODS: We subjected organic extracts of the PM to bioassay-directed fractionation by sequential elution on silica gel with solvents of increasing polarity to produce four fractions per fuel. We injected these onto high performance liquid chromatography to produce 62 sub-fractions per fraction based on chemical polarity and evaluated all fractions and sub-fractions for mutagenicity in Salmonella. We correlated the results with the concentrations of 32 polycyclic aromatic hydrocarbons (PAHs) in the fractions. RESULTS: The mutagenicity-emission factors of the fractions generally decreased with increasing concentrations of soy in the fuel. Despite the different chemical compositions of the fuels, the extractable organics of all four emissions had similar features: ∼60% of the mass was nonpolar, non-mutagenic compounds; most of the PAHs were polar; and most of the mutagenicity was due to weakly polar and polar compounds. Some of the mutagenicity of B20 was due to highly polar compounds. CONCLUSIONS: The PM from soy biodiesel emissions was less mutagenic than that from petroleum diesel, and this reduction was associated with reduced concentrations of various weakly polar, polar, and highly polar mutagens, including PAHs, aromatic amines, nitroarenes, and oxy-PAHs.

Health effects of soy-biodiesel emissions: mutagenicity-emission factors.

CONTEXT: Soy biodiesel is the predominant biodiesel fuel used in the USA, but only a few, frequently conflicting studies have examined the potential health effects of its emissions. OBJECTIVE: We combusted petroleum diesel (B0) and fuels with increasing percentages of soy methyl esters (B20, B50 and B100) and determined the mutagenicity-emission factors expressed as revertants/megajoule of thermal energy consumed (rev/MJ(th)). MATERIALS AND METHODS: We combusted each fuel in replicate in a small (4.3-kW) diesel engine without emission controls at a constant load, extracted organics from the particles with dichloromethane, determined the percentage of extractable organic material (EOM), and evaluated these extracts for mutagenicity in 16 strains/S9 combinations of Salmonella. RESULTS: Mutagenic potencies of the EOM did not differ significantly between replicate experiments for B0 and B100 but did for B20 and B50. B0 had the highest rev/MJ(th), and those of B20 and B100 were 50% and ∼85% lower, respectively, in strains that detect mutagenicity due to polycyclic aromatic hydrocarbons (PAHs), nitroarenes, aromatic amines or oxidative mutagens. For all strains, the rev/MJ(th) decreased with increasing biodiesel in the fuel. The emission factor for the 16 EPA Priority PAHs correlated strongly (r(2 )= 0.69) with the mutagenicity-emission factor in strain TA100 + S9, which detects PAHs. CONCLUSIONS: Under a constant load, soy-biodiesel emissions were 50-85% less mutagenic than those of petroleum diesel. Without additional emission controls, petroleum and biodiesel fuels had mutagenicity-emission factors between those of large utility-scale combustors (e.g. natural gas, coal, or oil) and inefficient open-burning (e.g. residential wood fireplaces).

Urinary mutagenicity and bladder cancer risk in northern New England.

The etiology of bladder cancer among never smokers without occupational or environmental exposure to established urothelial carcinogens remains unclear. Urinary mutagenicity is an integrative measure that reflects recent exposure to genotoxic agents. Here, we investigated its potential association with bladder cancer in rural northern New England. We analyzed 156 bladder cancer cases and 247 cancer-free controls from a large population-based case-control study conducted in Maine, New Hampshire, and Vermont. Overnight urine samples were deconjugated enzymatically and the extracted organics were assessed for mutagenicity using the plate-incorporation Ames assay with the Salmonella frameshift strain YG1041 + S9. Logistic regression was used to estimate the odds ratios (OR) and 95% confidence intervals (CI) of bladder cancer in relation to having mutagenic versus nonmutagenic urine, adjusted for age, sex, and state, and stratified by smoking status (never, former, and current). We found evidence for an association between having mutagenic urine and increased bladder cancer risk among never smokers (OR = 3.8, 95% CI: 1.3-11.2) but not among former or current smokers. Risk could not be estimated among current smokers because nearly all cases and controls had mutagenic urine. Urinary mutagenicity among never-smoking controls could not be explained by recent exposure to established occupational and environmental mutagenic bladder carcinogens evaluated in our study. Our findings suggest that among never smokers, urinary mutagenicity potentially reflects genotoxic exposure profiles relevant to bladder carcinogenesis. Future studies are needed to replicate our findings and identify compounds and their sources that influence bladder cancer risk.

Genotoxicity biomarkers associated with exposure to traffic and near-road atmospheres: a review.

Diesel and gasoline emissions, which are the primary components of traffic exhaust, are known or possible human carcinogens, respectively, and working or living near high-traffic roads is associated with various health effects, including cancer. To help understand the mechanistic basis for this observation, the present article reviews 63 studies on genotoxicity biomarkers in traffic-exposed subjects, with office workers being the typical control subjects. The six primary biomarkers used in these studies were the traditional cytogenetic end points, chromosome aberrations (CAs), micronucleus (MN) and sister chromatid exchange, and the standard molecular end points for DNA damage, (32)P-postlabeling, the comet assay and urinary 8-hydroxydeoxyguanosine. These six assays accounted for 74 of the 87 biomarker assessments reported in the studies; all six effectively distinguished traffic-exposed from control populations, giving an average 89% positive results among exposed versus control subjects. In addition, three genomic biomarkers effectively distinguished between the exposed and control populations; these assays measured changes in gene expression, leukocyte telomere length and DNA methylation. Nearly half of all of the studies included exposure assessments involving blood (primarily protein adducts), urine (primarily 1-hydroxypyrene) or air (primarily polycyclic aromatic hydrocarbons); these assays distinguished the exposed from the control subjects for the vast majority of the studies. All but three of the 63 reports were environmental studies that investigated 18 general exposure categories, such as traffic police and automobile/bus mechanics. The studies were performed in 20 countries; however, nearly all of the environmental studies were performed in Europe and Asia, with only one each from Africa, North America and South America. Given that several of the biomarkers are associated with increased cancer risk, including CAs, MNs and altered telomere length, the data reviewed here provide strong mechanistic support for the ability of chronic exposure to traffic exhaust to increase cancer risk.

Harnessing genomics to identify environmental determinants of heritable disease.

Next-generation sequencing technologies can now be used to directly measure heritable de novo DNA sequence mutations in humans. However, these techniques have not been used to examine environmental factors that induce such mutations and their associated diseases. To address this issue, a working group on environmentally induced germline mutation analysis (ENIGMA) met in October 2011 to propose the necessary foundational studies, which include sequencing of parent-offspring trios from highly exposed human populations, and controlled dose-response experiments in animals. These studies will establish background levels of variability in germline mutation rates and identify environmental agents that influence these rates and heritable disease. Guidance for the types of exposures to examine come from rodent studies that have identified agents such as cancer chemotherapeutic drugs, ionizing radiation, cigarette smoke, and air pollution as germ-cell mutagens. Research is urgently needed to establish the health consequences of parental exposures on subsequent generations.

Analysis of chemical structures and mutations detected by Salmonella TA98 and TA100.

As part of an analysis performed under the auspices of the International Workshop on Genotoxicity Testing (IWGT) in 2017, we and others showed that Salmonella frameshift strain TA98 and base-substitution strain TA100 together + /- S9 detected 93% of the mutagens detected by all the bacterial strains recommended by OECD TG471 (Williams et al., Mutation Res. 848:503081, 2019). We have extended this analysis by identifying the numbers and chemical classes of chemicals detected by these two strains either alone or in combination, including the role of S9. Using the Leadscope 2021 SAR Genetox database containing > 21,900 compounds, our dataset containing 7170 compounds tested in both TA98 and TA100. Together, TA98 and TA100 detected 94% (3733/3981) of the mutagens detected using all the TG471-recommended bacterial strains; 39% were mutagenic in one or both strains. TA100 detected 77% of all of these mutagens and TA98 70%. Considering the overlap of detection by both strains, 12% of these mutagens were detected only by TA98 and 19% only by TA100. In the absence of S9, sensitivity dropped by 31% for TA98 and 29% for TA100. Overall, 32% of the mutagens required S9 for detection by either strain; 9% were detected only without S9. Using the 2021 Leadscope Genetox Expert Alerts, TA100 detected 18 mutagenic alerting chemical classes with better sensitivity than TA98, whereas TA98 detected 10 classes better than TA100. TA100 detected more chemical classes than did TA98, especially hydrazines, azides, various di- and tri-halides, various nitrosamines, epoxides, aziridines, difurans, and half-mustards; TA98 especially detected polycyclic primary amines, various aromatic amines, polycyclic aromatic hydrocarbons, triazines, and dibenzo-furans. Model compounds with these structures induce primarily G to T mutations in TA100 and/or a hotspot GC deletion in TA98. Both TA98 and TA100 + /- S9 are needed for adequate mutagenicity screening with the Salmonella (Ames) assay.

Mutagenicity of the organic fraction of World Trade Center dust.

Most studies of the health effects and chemical characterization of the dust resulting from the catastrophic collapse of the World Trade Center (WTC) on September 11, 2001, have focused on the large inorganic fraction of the dust; however, chemical analyses have identified mutagens and carcinogens in the smaller organic fraction. Here, we determined the mutagenicity of the organic fraction of WTC dust in Salmonella. Only 0.74% of the mass of the particulate matter (PM) <53 µm in diameter was extractable organic matter (EOM). Because the EOM was 10 times more mutagenic in TA100 +S9 than in TA98 +S9 and was negative in TA98 -S9, we inferred, respectively, that polycyclic aromatic hydrocarbons (PAHs) played a role in the mutagenicity and not nitroarenes. In TA98 +S9, the mutagenic potency of the EOM (0.1 revertant/µg EOM) was within the range of EOMs from air and combustion emissions. However, the EOM-based mutagenic potency of the particles (0.0007 revertants/µg PM) was 1-2 orders of magnitude lower than values from a review of 50 combustion emissions and various air samples. We calculated that 37 PAHs analyzed previously in WTC EOM were 5.4% of the EOM mass and 0.04% of the PM mass; some air contained 0.3 µg WTC EOM/m3 (0.02 µg PAHs/m3 ). Populations exposed to WTC dust have elevated levels of prostate and thyroid cancer but not lung cancer. Our data support earlier estimates that PAH-associated cancer risk among this population, for example, PAH-associated lung cancer, was unlikely to be significantly elevated relative to background PAH exposures.