Mutagenicity and DNA adduct formation of PAH, nitro-PAH, and oxy-PAH fractions of atmospheric particulate matter from São Paulo, Brazil.

Urban particulate matter (UPM) contributes to lung cancer incidence. Here, we have studied the mutagenic activity and DNA adduct-forming ability of fractionated UPM extractable organic matter (EOM). UPM was collected with a high-volume sampler in June 2004 at two sites, one at street level adjacent to a roadway and the other inside a park within the urban area of the city of São Paulo, Brazil. UPM was extracted using dichloromethane, and the resulting EOM was separated by HPLC to obtain PAH, nitro-PAH, and oxy-PAH fractions which were tested for mutagenicity with the Salmonella strains TA98 and YG1041 with and without S9 metabolic activation. The PAH fraction from both sites showed negligible mutagenic activity in both strains. The highest mutagenic activity was found for the nitro-PAH fraction using YG1041 without metabolic activation; however, results were comparable for both sites. The nitro-PAH and oxy-PAH fractions were incubated with calf thymus DNA under reductive conditions appropriate for the activation of nitro aromatic compounds, then DNA adduct patterns and levels were determined with thin-layer chromatography (TLC) 32P-postlabeling method using two enrichment procedures-nuclease P1 digestion and butanol extraction. Reductively activated fractions from both sites produced diagonal radioactive zones (DRZ) of putative aromatic DNA adducts on thin layer plates with both enrichment procedures. No such DRZ were observed in control experiments using fractions from unexposed filters or from incubations without activating system. Total adduct levels produced by the nitro-PAH fractions were similar for both sites ranging from 30 to 45 adducts per 10(8) normal nucleotides. In contrast, the DNA binding of reductively activated oxy-PAH fractions was three times higher and the adduct pattern consisted of multiple discrete spots along the diagonal line on the thin layer plates. However, DNA adduct levels were not significantly different between the sampling sites. Both samples presented the same levels of mutagenic activity. The response in the Salmonella assay was typical of nitroaromatics. Although, more mutagenic activity was related to the nitro-PAH fraction in the Salmonella assay, the oxy-PAH fractions showed the highest DNA adduct levels. More studies are needed to elucidate the nature of the genotoxicants occurring in São Paulo atmospheric samples.

Integrated disinfection by-products research: salmonella mutagenicity of water concentrates disinfected by chlorination and ozonation/postchlorination.

Although chemical disinfection of drinking water is a highly protective public health practice, the disinfection process is known to produce toxic contaminants. Epidemiological studies associate chlorinated drinking water with quantitatively increased risks of rectal, kidney, and bladder cancer. One study found a significant exposure-response association between water mutagenicity and relative risk for bladder and kidney cancer. A number of studies found that several types of disinfection processes increase the level of mutagens detected by the Salmonella assay. As part of a comprehensive study to examine chlorinated and ozonated/postchlorinated drinking water for toxicological contaminants, the Salmonella mutagenicity assay was used to screen both volatile and nonvolatile organic components. The assay also compared the use of reverse osmosis and XAD resin procedures for concentrating the nonvolatile components. Companion papers provide the results from other toxicological assays and chemical analysis of the drinking water samples. The volatile components of the ozonated/postchlorinated and chlorinated water samples and a trihalomethane mixture were mutagenic to a Salmonella tester strain transfected with a rat theta-class glutathione S-transferase and predominantly nonmutagenic in the control strain. In this study, the nonvolatile XAD concentrate of the untreated water possessed a low level of mutagenic activity. However, compared to the levels of mutagenicity in the finished water XAD concentrates, the contribution from the settled source water was minimal. The mutagenicity seen in the reverse osmosis concentrates was < 50% of that seen in the XAD concentrates. Overall, mutagenic responses were similar to those observed in other North American studies and provide evidence that the pilot plant produced disinfection by-products similar to that seen in other studies.

A review of the mutagenicity and rodent carcinogenicity of ambient air.

Although ambient air was first shown to be carcinogenic in 1947 and mutagenic in 1975, no overarching review of the subsequent literature has been produced. Recently, Claxton et al. [L.D. Claxton, P.P. Matthews, S.H. Warren, The genotoxicity of ambient outdoor air, a review: Salmonella mutagenicity, Mutat. Res./Rev. Mutat. Res. 567 (2004) 347-399] reviewed the literature on the mutagenicity of urban air in the Salmonella mutagenicity assay. Here, we review the literature on the mutagenicity of urban air in other test systems and review the carcinogenicity of urban air in experimental systems. Urban air was carcinogenic in most of the reports involving rodents. Studies ascribed carcinogenic activity primarily to PAHs, nitroarenes, and other aromatic compounds. Atmospheric conditions, along with the levels and types of pollutants, contributed to the variations in carcinogenic and mutagenic activity of air from different metropolitan areas. The majority of the mutagenesis literature was in the Salmonella assay (50%), with plant systems accounting for most of the rest (31%). The present data give little support to the use of plant systems to compare air mutagenicity among multiple sites or studies. Studies in mice have shown that particulate air pollution causes germ-cell mutations. Air sheds contain similar types and classes of mutagens; however, the levels of these compounds vary considerably among air sheds. Combustion emissions were associated with much of the mutagenicity and carcinogenicity of urban air. Most studies focused on the particulate fraction; thus, additional work is needed on the volatile and semi-volatile fractions, metals, and atmospheric transformation. Smaller particles have greater percentages of extractable organic material and are more mutagenic than larger particles. Although hundreds of genotoxic compounds have been identified in ambient air, only a few (<25) are routinely monitored, emphasizing the value of coupling bioassay with chemistry in the monitoring of air for carcinogenic and mutagenic activities and compounds.

Review of the Salmonella typhimurium mutagenicity of benzidine, benzidine analogues, and benzidine-based dyes.

We have reviewed the mutagenicity of benzidine analogues (including benzidine-based dyes), with a primary emphasis on evaluating results of the Salmonella/microsome mutagenicity assay. Many of these amines are mutagenic in tester strains TA98 and TA100 but require exogenous mammalian activation (S9) for activity. A few amines with halogen or nitro-groups in the structure are direct-acting mutagens. The addition of a sulfonic acid moiety to the molecule of benzidine reduced the mutagenicity of benzidine; whereas, methoxy, chloro, or methyl group additions did not. Complexation with a metal ion also decreased the mutagenicity. A substitution of an alkyl group on the ortho position next to an amine group also influenced the mutagenicity. Most carcinogenic benzidine analogues are mutagenic, and their metabolism to electrophiles that interact with DNA, leading to mutations, plays a central role in their carcinogenesis.

Evaluation of new 2,2'-dimethyl-5,5'-dipropoxybenzidine- and 3,3'-dipropoxybenzidine-based direct dye analogs for mutagenic activity by use of the Salmonella/mammalian mutagenicity assay.

As part of a continuing study aimed at establishing structure-activity relationships and heuristic principles useful for the design of non-genotoxic azo dyes, a series of new direct dyes based on two non-mutagenic benzidine analogs, 2,2'-dimethyl-5,5'-dipropoxybenzidine and 3,3'-dipropoxybenzidine, were evaluated for mutagenic activity in Salmonella typhimurium strains TA98 and TA100. These strains are widely used for mutagenicity screening and have been shown to detect the mutagenic activity of benzidine analogs. While some toxicity was seen with some dyes at high doses, all of the dyes examined were judged non-mutagenic with and without metabolic activation in the standard Salmonella plate-incorporation assay. The results in the standard test are consistent with the properties of the diamines themselves. However, only one of the dyes was non-mutagenic when a reductive-metabolism pre-incubation assay was used. The results of this study suggest that although benzidine analogs are potential replacements for benzidine, there is a need to understand which mutagenic products are produced when reductive metabolism is present. There is also a need to know whether or not metal complexes of these dyes are mutagenic. Such information will allow the development of new non-mutagenic azo dyes.

The mutation spectra of chlorinated drinking water samples using the base-specific TA7000 strains of Salmonella in the microsuspension assay.

Mutation spectra analysis can provide important information about the types of genotoxic compounds that can be present in environmental samples. In this study, we used the TA7000 base-specific Salmonella typhimurium tester strains to characterize water samples from two drinking water treatment plants (DWTPs) in São Paulo, Brazil. Because of the small sample sizes of these environmental samples, the use of the microsuspension protocol was necessary. Acidic extracts of drinking water samples from the two DWTPs gave similar responses in the TA7000 strains and caused primarily CG to AT transversions. It is likely that halogenated disinfection by-products, generated during the chlorination of water, are causing the response seen with the TA7000 strains.

Scientific authorship. Part 1. A window into scientific fraud?

The examination of a single scientific manuscript seldom alerts scientists, reviewers, editors, and scientific administrators to the fabrication and falsification of data and information. This review shows that most documented cases of scientific fraud involve falsification (altering truthful information) and fabrication (inventing information where none previously existed). Plagiarism is much less frequent. The review of published accounts also shows that the publication of scientific papers containing recognizable fraudulent material is very low, probably less than 0.02% and extremely difficult to detect. Because most reported cases of fraud have involved research done at prestigious organizations with distinguished co-authors, and that is published in journals with exacting review processes, it becomes evident that some unscrupulous scientists are adept at fabricating and falsifying data. However, "significant" scientific fraud is detected when scientists repeatedly report results that cannot be independently verified, when colleagues report suspicious behavior, or scientific audits are performed. This review documents and compares many of the better-known cases of scientific fraud. Fraudulent behavior has served as the impetus for the scientific community to develop publication procedures and guidelines that help to guard against not only fraudulent behavior but also against other types of unethical or undesirable behaviors. A companion paper reviews the non-fraudulent issues associated with scientific publication.

Scientific authorship. Part 2. History, recurring issues, practices, and guidelines.

One challenge for most scientists is avoiding and resolving issues that center around authorship and the publishing of scientific manuscripts. While trying to place the research in proper context, impart new knowledge, follow proper guidelines, and publish in the most appropriate journal, the scientist often must deal with multi-collaborator issues like authorship allocation, trust and dependence, and resolution of publication conflicts. Most guidelines regarding publications, commentaries, and editorials have evolved from the ranks of editors in an effort to diminish the issues that faced them as editors. For example, the Ingelfinger rule attempts to prevent duplicate publications of the same study. This paper provides a historical overview of commonly encountered scientific authorship issues, a comparison of opinions on these issues, and the influence of various organizations and guidelines in regards to these issues. For example, a number of organizations provide guidelines for author allocation; however, a comparison shows that these guidelines differ on who should be an author, rules for ordering authors, and the level of responsibility for coauthors. Needs that emerge from this review are (a) a need for more controlled studies on authorship issues, (b) an increased awareness and a buy-in to consensus views by non-editor groups, e.g., managers, authors, reviewers, and scientific societies, and (c) a need for editors to express a greater understanding of authors' dilemmas and to exhibit greater flexibility. Also needed are occasions (e.g., an international congress) when editors and others (managers, authors, etc.) can directly exchange views, develop consensus approaches and solutions, and seek agreement on how to resolve authorship issues. Open dialogue is healthy, and it is essential for scientific integrity to be protected so that younger scientists can confidently follow the lead of their predecessors.

Mutagenicity evaluation of the commercial product CI Disperse Blue 291 using different protocols of the Salmonella assay.

Textile dyes can enter the water ecosystem through wastewater discharges potentially exposing humans through the consumption of water and food. The commercial disperse dye product CI Disperse Blue 291 containing the aminoazobenzene 2-[(2-bromo-4,6-dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide (CAS registry no. 56548-64-2) was tested for mutagenic activity in the Salmonella assay. We used strains with different levels of nitroreductase and O-acetyltransferase (i.e., TA98DNP6, YG1024, and YG1041) that are relevant enzymes in the activation of nitrocompounds by the intestinal microflora. The commercial product tested also was mutagenic for TA1537, TA1538, TA98 and TA100. Presence of the pKM101 plasmid and the addition of S9 enhanced the mutagenic response. Specialized strains showed that both nitroreductase and O-acetyltransferase are important in activation of the product. The highest potency obtained was 240 revertants per microgram for YG1041 in the presence of S9. Besides being able to cause frameshift mutations (hisd3052), the dye was able to cause all types of base pair substitution with a preference for TA to AT; CG to TA and CG to AT changes. With these results clearly showing that the bacterial nitroreductase and O-acetyltransferase metabolites of this compound are mutagenic, there is a need to test this dye using in vivo systems to verify possible adverse effects of this product in mammalian tissues.

The contribution of azo dyes to the mutagenic activity of the Cristais River.

To verify whether dyes emitted within the discharge of a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, Sao Paulo, Brazil, we chemically characterized the following mutagenic samples: the treated industrial effluent, raw and treated water, and the sludge produced by a Drinking Water Treatment Plant (DWTP) located approximately 6 km from the industrial discharge. Considering that 20% of the dyes used for coloring activities might be lost to wastewaters and knowing that several dyes have mutagenic activity, we decided to analyze the samples for the presence of dyes. Thin layer chromatographic analysis indicated the presence of three prevalent dyes in all samples, except for the drinking water. This combination of dyes corresponded to a commercial product used by the industry, and it tested positive in the Salmonella assay. The structures of the dye components were determined using proton magnetic resonance and mass spectrometric (MS) methods, and the dyes were tested for mutagenicity. The blue component was identified as the C.I. Disperse Blue 373, the violet as C.I. Disperse Violet 93, and the orange as C.I. Disperse Orange 37. The dyes showed mutagenic responses of 6300, 4600, and 280 revertants/microg for YG1041 with S9 respectively. A bioassay-directed fractionation/chemical analysis showed that the C.I. Disperse Blue 373 contributed 55% of the mutagenic activity of the DWTP sludge. We showed that these dyes contributed to the mutagenic activity found in the Cristais River environmental samples analyzed and are indirectly affecting the quality of the related drinking water. Therefore, we believe that this type of discharge should be more thoroughly characterized chemically and toxicologically. Additionally, human and ecological risks associated with the release of dye processing plant effluents should be more fully investigated, especially where the resultant water is taken for human consumption.

Biodegradation of simple chemical mixtures in soil.

Exogenous microorganisms often are used to enhance bioremediation. This study compared the capabilities of two exogenous microbial cultures and an indigenous population to detoxify a Weswood silt loam soil amended with a simple chemical mixture. The first three treatments were unamended soils inoculated with either indigenous microorganisms, Pseudomonas aeruginosa, or Phanerochaete sordida. Three additional treatments consisted of soil amended with benzo[a]pyrene, pentachlorophenol, and 2,4,6-trinitrotoluene, which were inoculated with either indigenous microorganisms, P. aeruginosa, or P. sordida. Samples were collected from the soils at several time points from 0 through 540 or 720 d, sequentially extracted with methylene chloride and methanol, and analyzed for genotoxicity (using the Salmonella/microsome assay) and chemical degradation. Although the indigenous microorganisms were effective for removal of benzo[a]pyrene, the Pseudomonas bacteria exhibited slightly greater removal rates for 2,4,6,-trinitrotoluene. The fungal cultures were significantly more effective at degrading pentachlorophenol. The day 540 extracts from all model chemical-amended treatments were genotoxic. In most cases, the day 540 extracts were more genotoxic than the day 0 extracts. The results suggest that, under appropriate conditions, enriched cultures of microorganisms may have an increased capacity to degrade individual chemicals. However, the products of degradation in some cases might be more genotoxic than the parent compounds.

The history, genotoxicity and carcinogenicity of carbon-based fuels and their emissions: part 4 - alternative fuels.

Much progress has been made in reducing the pollutants emitted from various combustors (including diesel engines and power plants) by the use of alternative fuels; however, much more progress is needed. Not only must researchers improve fuels and combustors, but also there is a need to improve the toxicology testing and analytical chemistry methods associated with these complex mixtures. Emissions from many alternative carbonaceous fuels are mutagenic and carcinogenic. Depending on their source and derivation, alternative carbonaceous fuels before combustion may or may not be genotoxic; however, in order to know their genotoxicity, appropriate chemical analysis and/or bioassay must be performed. Newly developed fuels and combustors must be tested to determine if they provide a public health advantage over existing technologies - including what tradeoffs can be expected (e.g., decreasing levels of PAHs versus increasing levels of NOx and possibly nitroarenes in ambient air). Another need is to improve exposure estimations which presently are a weak link in doing risk analyses.

The history, genotoxicity, and carcinogenicity of carbon-based fuels and their emissions: part 5. Summary, comparisons, and conclusions.

As seen through the previous reviews, each carbonaceous source of energy is associated with genotoxic and carcinogenic health risks; however, energy use is central to human society and provides many health benefits. These reviews examined the genotoxicity of carbonaceous sources of energy, focusing on the impacts due to the combustion of fuels and biomass. In previous reviews, information and data were used to examine occupational, industrial, household, and general environmental pollution as well as laboratory research. In this final summation, the effort is not only to summarize the previous reviews but to provide additional information to support any final conclusions. Included in the final observations are: (1) emissions from combusted carbonaceous fuels are very likely to include genotoxicants and/or carcinogens, and, as such, they can considerably increase the risk of adverse health effects in exposed humans, (2) environmental transformation is likely to increase genotoxicity of emissions, and (3) the world's poor households have an increased health risk because they have limited access to clean fuels and electricity. Because carbonaceous fuel emissions are highly complex, risk assessments are difficult; however, decision makers have many toxicological approaches for evaluating emissions. Although energy efficiency brings many benefits, it also involves health risks, as do renewable energy systems, if not managed carefully. The reviews do not examine climate change or non-carbonaceous fuels (e.g., nuclear fuels). Because these are not papers about the risk assessment or regulation of pollutants from carbon-based fuels, the discussions of regulations were to place research, concerns, and actions into a historical reference for the reader.

The history, genotoxicity, and carcinogenicity of carbon-based fuels and their emissions. Part 3: diesel and gasoline.

Within this review the genotoxicity of diesel and gasoline fuels and emissions is placed in an historical context. New technologies have changed the composition of transportation methods considerably, reducing emissions of many of the components of health concern. The similarity of modern diesel and gasoline fuels and emissions to other carbonaceous fuels and emissions is striking. Recently an International Agency for Research on Cancer (IARC) Working Group concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust (Group 1). In addition, the Working Group found that diesel exhaust has "a positive association (limited evidence) with an increased risk of bladder cancer." Like most other carbonaceous fuel emissions, diesel and gasoline exhausts contain toxic levels of respirable particles (PM <2.5µm) and polycyclic aromatic hydrocarbons. However, the level of toxic components in exhausts from diesel and gasoline emissions has declined in certain regions over time because of changes in engine design, the development of better aftertreatment devices (e.g., catalysts), increased fuel economy, changes in the fuels and additives used, and greater regulation. Additional research and better exposure assessments are needed so that decision makers and the public can decide to what extent diesel and gasoline engines should be replaced.

Survey of the mutagenicity of surface water, sediments, and drinking water from the Penobscot Indian Nation.

U.S. Environmental Protection Agency (US EPA) Regional Applied Research Effort (RARE) projects address the effects of environmental pollutants in a particular region on the health of the population in that region. This report is part of a RARE project that addresses this for the Penobscot Indian Nation (PIN), Penobscot Island, Maine, U.S., where the Penobscot River has had fish advisories for many years due to high levels of mercury. We used the Salmonella mutagenicity assay with strains TA100, TA98, YG1041, and YG1042 with and without metabolic activation to assess the mutagenic potencies of organic extracts of the Penobscot River water and sediment, as well as drinking-water samples, all collected by the PIN Department of Natural Resources. The source water for the PIN drinking water is gravel-packed groundwater wells adjacent to the Penobscot River. Most samples of all extracts were either not mutagenic or had low to moderate mutagenic potencies. The average mutagenic potencies (revertants/L-equivalent) were 337 for the drinking-water extracts and 177 for the river-water extracts; the average mutagenic potency for the river-sediment extracts was 244 revertants(g-equivalent)(-1). This part of the RARE project showed that extracts of the Penobscot River water and sediments and Penobscot drinking water have little to no mutagenic activity that might be due to the classes of compounds that the Salmonella mutagenicity assay detects, such as polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (nitroarenes), and aromatic amines. This study is the first to examine the mutagenicity of environmental samples from a tribal nation in the U.S.

Mutagens in contaminated soil: a review.

The intentional and accidental discharges of toxic pollutants into the lithosphere results in soil contamination. In some cases (e.g., wood preserving wastes, coal-tar, airborne combustion by-products), the contaminated soil constitutes a genotoxic hazard. This work is a comprehensive review of published information on soil mutagenicity. In total, 1312 assessments of genotoxic activity from 118 works were examined. The majority of the assessments (37.6%) employed the Salmonella mutagenicity test with strains TA98 and/or TA100. An additional 37.6% of the assessments employed a variety of plant species (e.g., Tradescantia clone 4430, Vicia faba, Zea mays, Allium cepa) to assess mutagenic activity. The compiled data on Salmonella mutagenicity indicates significant differences (p<0.0001) in mean potency (revertents per gram dry weight) between industrial, urban, and rural/agricultural sites. Additional analyses showed significant empirical relationships between S9-activated TA98 mutagenicity and soil polycyclic aromatic hydrocarbon (PAH) concentration (r2=0.19 to 0.25, p<0.0001), and between direct-acting TA98 mutagenicity and soil dinitropyrene (DNP) concentration (r2=0.87, p<0.0001). The plant assay data revealed excellent response ranges and significant differences between heavily contaminated, industrial, rural/agricultural, and reference sites, for the anaphase aberration in Allium cepa (direct soil contact) and the waxy locus mutation assay in Zea mays (direct soil contact). The Tradescantia assays appeared to be less responsive, particularly for exposures to aqueous soil leachates. Additional data analyses showed empirical relationships between anaphase aberrations in Allium, or mutations in Arabidopsis, and the 137Cs contamination of soils. Induction of micronuclei in Tradescantia is significantly related to the soil concentration of several metals (e.g., Sb, Cu, Cr, As, Pb, Cd, Ni, Zn). Review of published remediation exercises showed effective removal of genotoxic petrochemical wastes within one year. Remediation of more refractory genotoxic material (e.g., explosives, creosote) frequently showed increases in mutagenic hazard that remained for extended periods. Despite substantial contamination and mutagenic hazards, the risk of adverse effect (e.g., mutation, cancer) in humans or terrestrial biota is difficult to quantify.

Developing azo and formazan dyes based on environmental considerations: Salmonella mutagenicity.

In previous papers, the synthesis and chemical properties of iron-complexed azo and formazan dyes were reported. It was shown that in certain cases iron could be substituted for the traditionally used metals such as chromium and cobalt, without having an adverse effect on dye stability. While these results suggested that the iron analogs were potential replacements for the commercially used chromium and cobalt prototypes, characterization of potentially adverse environmental effects of the new dyes was deemed an essential step in their further development. The present paper provides results from using the Salmonella/mammalian microsome assay to determine the mutagenicity of some important commercial metal complexed dyes, their unmetallized forms, and the corresponding iron-complexed analogs. The study compared the mutagenic properties of six unmetallized azo dyes, six commercial cobalt- or chromium-complexed azo dyes, six iron-complexed azo dyes, six unmetallized formazan dyes, and six iron-complexed formazan dyes. The results of this study suggest that the mutagenicity of the unmetallized dye precursors plays a role in determining the mutagenicity of the iron-complexes. For the monoazo dye containing a nitro group, metal complex formation using iron or chromium decreased or removed mutagenicity in TA100; however, little reduction in mutagenicity was noted in TA98. For the formazan dye containing a nitro group, metal-complex formation using iron increased mutagenicity. Results varied for metal-complexes of azo and formazan dyes without nitro groups, but in general, the metal-complexed dyes based on mutagenic ligands were also mutagenic, while those dyes based on nonmutagenic ligands were nonmutagenic.

The genotoxicity of ambient outdoor air, a review: Salmonella mutagenicity.

Mutagens in urban air pollution come from anthropogenic sources (especially combustion sources) and are products of airborne chemical reactions. Bacterial mutation tests have been used for large, multi-site, and/or time series studies, for bioassay-directed fractionation studies, for identifying the presence of specific classes of mutagens, and for doing site- or source-comparisons for relative levels of airborne mutagens. Early research recognized that although carcinogenic PAHs were present in air samples they could not account for the majority of the mutagenic activity detected. The mutagenicity of airborne particulate organics is due to at least 500 identified compounds from varying chemical classes. Bioassay-directed fractionation studies for identifying toxicants are difficult to compare because they do not identify all of the mutagens present, and both the analytical and bioassay protocols vary from study to study. However, these studies show that the majority of mutagenicity is usually associated with moderately polar/highly polar classes of compounds that tend to contain nitroaromatic compounds, aromatic amines, and aromatic ketones. Smog chamber studies have shown that mutagenic aliphatic and aromatic nitrogen-containing compounds are produced in the atmosphere when organic compounds (even non-mutagenic compounds) are exposed to nitrogen oxides and sunlight. Reactions that occur in the atmosphere, therefore, can have a profound effect on the genotoxic burden of ambient air. This review illustrates that the mutagenesis protocol and tester strains should be selected based on the design and purpose of the study and that the correlation with animal cancer bioassay results depends upon chemical class. Future emphasis needs to be placed on volatile and semi-volatile genotoxicants, and on multi-national studies that identify, quantify, and apportion mutagenicity. Initial efforts at replacing the Salmonella assay for ambient air studies with some emerging technology should be initiated.

Investigating the sources of the mutagenic activity found in a river using the Salmonella assay and different water extraction procedures.

In the routine São Paulo state (Brazil) surface water quality-monitoring program, which includes the Salmonella microsome mutagenicity assay as one of its parameters, a river where water is taken and treated for drinking water purposes has repeatedly shown mutagenic activity. A textile dyeing facility employing azo-type dyes was the only identifiable source of mutagenic compounds. We extracted the river and drinking water samples with XAD4 at neutral and acidic pH and with blue rayon, which selectively adsorbs polycyclic compounds. We tested the industrial effluent, raw, and treated water and sediment samples with YG1041 and YG1042 and compared the results with the TA98 and TA100 strains. The elevated mutagenicity detected with YG-strains suggested that nitroaromatics and/or aromatic amines were causing the mutagenicity detected in the samples analyzed. Positive responses for the blue rayon extracts indicated that mutagenic polycyclic compounds were present in the water samples analyzed. The mutagen or mixture of mutagens present in the effluent and water samples cause mainly frameshift mutations and are positive with and without metabolic activation. The Salmonella assay combined with different extraction procedures proved to be very useful in the identification of the origin of the pollution and in the identification of the classes of chemical compounds causing the mutagenic activity in the river analyzed.

The history, genotoxicity, and carcinogenicity of carbon-based fuels and their emissions. Part 2: solid fuels.

The combustion of solid fuels (like wood, animal dung, and coal) usually involves elevated temperatures and altered pressures and genotoxicants (e.g., PAHs) are likely to form. These substances are carcinogenic in experimental animals, and epidemiological studies implicate these fuels (especially their emissions) as carcinogens in man. Globally, ∼50% of all households and ∼90% of all rural households use solid fuels for cooking or heating and these fuels often are burnt in simple stoves with very incomplete combustion. Exposed women and children often exhibit low birth weight, increased infant and perinatal mortality, head and neck cancer, and lung cancer although few studies have measured exposure directly. Today, households that cannot meet the expense of fuels like kerosene, liquefied petroleum gas, and electricity resort to collecting wood, agricultural residue, and animal dung to use as household fuels. In the more developed countries, solid fuels are often used for electric power generation providing more than half of the electricity generated in the United States. The world's coal reserves, which equal approximately one exagram, equal ∼1 trillion barrels of crude oil (comparable to all the world's known oil reserves) and could last for 600 years. Studies show that the PAHs that are identified in solid fuel emissions react with NO2 to form direct-acting mutagens. In summary, many of the measured genotoxicants found in both the indoor and electricity-generating combustors are the same; therefore, the severity of the health effects vary with exposure and with the health status of the exposed population.