A comparative assessment of Boise, Idaho, ambient air fine particle samples using the plate and microsuspension Salmonella mutagenicity assays

Comparative mutagenic activity of atmospheric particulate matter from limeira, stockholm, and kyoto

Atmospheric particulate matter (PM) organic fractions from urban centers are frequently mutagenic for the Salmonella/microsome assay. This mutagenicity is related to both primary and secondary pollutants, and meteorological conditions have great influence on the secondary pollutant's formation. Our objective was to compare the mutagenicity of atmospheric total suspended particulates (TSP) from three cities with marked different meteorological conditions and TSP concentrations: Limeira (Brazil) with 99.0 μg/m³ , Stockholm (Sweden) with 6.2 μg/m³ , and Kyoto (Japan) with 28.0 μg/m³ . For comparison, we used the same batch of filters, sample extraction method, and Salmonella/microsome testing protocol with 11 strains of Salmonella with and without metabolic activation. Samples were collected during winter and pooled into one single extract representing each city. All samples were mutagenic for all tested strains, except for TA102. Based on the strain's selectivity, nitroarenes, polycyclic aromatic hydrocarbons, and aromatic amines play a predominant role in the mutagenicity of these samples. The mutagenic potencies expressed by mass of extracted organic material (EOM; revertants/μg EOM) were similar (~twofold difference) among the cities, despite differences in meteorological conditions and pollution sources. In contrast, the mutagenic potencies expressed by air volume (rev/m³ ) varied ~20-fold, with Limeira > Kyoto ≈ Stockholm. These results are the first systematic assessment of air mutagenicity from cities on three continents using the same protocols. The results confirm that the mutagenic potency expressed by EOM mass is similar regardless of continent of origin, whereas the mutagenic potency expressed by air volume can vary by orders of magnitude. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

Oxidative stress, DNA damage, and mutagenicity induced by the extractable organic matter of airborne particulates on bacterial models

The biological activity induced by the extractable organic matter (EOM) of size-segregated airborne Particulate Matter (PM) from two urban sites, urban traffic (UT) and urban background (UB), was assessed by using bacterial assays. The Gram-negative Escherichia coli (E. coli) coliform bacterium was used to measure the intracellular formation of Reactive Oxygen Species (ROS) by employing the Nitroblue tetrazolium (NBT) reduction assay and the lipid peroxidation by malondialdehyde (MDA) measurement. To the best of our knowledge, this is the first study using E. coli for assessing the bioactivity of ambient air in term of oxidative mechanism studies. E. coli BL21 cells were further used for DNA damage assessment by employing the reporter (β-galactosidase) gene expression assay. The bacterial strain S. typhimurium TA100 was used to assess the mutagenic potential of PM by employing the well-known mutation assay (Ames test). Four PM size fractions were assessed for bioactivity, specifically the quasi-ultrafine mode (<0.49 μm), the upper accumulation mode (0.49-0.97 μm), the upper fine mode (0.97-3 μm), and the coarse mode (>3.0 μm). The EOM of each PM sample included three organic fractions of successively increased polarity: the non-polar organic fraction (NPOF), the moderately polar organic fraction (MPOF), and the polar organic fraction (POF). The toxicological endpoints induced by each organic fraction were correlated with the concentrations of various organic chemical components determined in previous studies in an attempt to identify the chemical classes involved.

Mutagenicity profile of atmospheric particulate matter in a small urban center subjected to airborne emission from vehicle traffic and sugar cane burning

Atmospheric particulate matter (PM) is genotoxic and recently was classified as carcinogenic to humans by the International Agency for Research on Cancer. PM chemical composition varies depending on source and atmospheric conditions. The Salmonella/microsome assay is the most used mutagenicity test and can identify the major chemical classes responsible for observed mutagenicity. The objective of this work was to characterize the mutagenicity of PM samples from a countryside city, Limeira, Brazil, which is influenced by heavy traffic and sugar cane biomass burning. Six samples of total PM were collected. Air mass backward trajectories were calculated. Organic extracts were assayed using the Salmonella/microsome microsuspension mutagenicity assay using TA98, YG1041, and TA1538, with and without metabolic activation (S9). YG1041 was the most sensitive strain and mutagenicity reached 9,700 revertants per m(3) without metabolic activation. Potency for TA1538 was higher than TA98, indicating that this strain should be considered in air mutagenicity studies. The increased response to YG1041 relative to TA98, and the decreased response with S9, suggests that nitroaromatics are the major contributors. Limeira is among the most mutagenic cities in the world. High mutagenicity in Limeira seems to occur when the air mass from the area of sugarcane production is mixed with air from the region impacted by anthropogenic activities such as traffic. An increase in the formation of nitro-polycyclic aromatic hydrocarbons may result from longer contact time between the aromatic compounds and the atmosphere with high NOx and ozone concentration, although more studies are required to confirm this hypothesis.

Monitoring of volatile and non-volatile urban air genotoxins using bacteria, human cells and plants

Urban air contains many mutagenic pollutants. This research aimed to investigate the presence of mutagens in the air by short-term mutagenicity tests using bacteria, human cells and plants. Inflorescences of Tradescantia were exposed to air in situ for 6h, once a month from January to May, to monitor volatile compounds and micronuclei frequency was computed. On the same days PM10 was collected continuously for 24h. Half of each filter was extracted with organic solvents and studied by means of the Ames test, using Salmonella typhimurium TA98 and TA100 strains, and the comet assay on human leukocytes. A quarter of each filter was extracted with distilled water in which Tradescantia was exposed. PM10 concentration was particularly high in the winter season (> 50 μg/m(3)). In situ exposure of inflorescences to urban air induced a significant increase in micronuclei frequency at all the sites considered, but only in January (p < 0.01). Aqueous extracts collected in January and February induced genotoxic effects in Tradescantia exposed in the laboratory (p < 0.01). Ames test showed that organic extracts of winter urban air were able to induce genetic mutations in S. typhimurium TA98 strain (± S9), but not in TA100 strain, with a revertants/plate number nine times higher than the negative control. Comet assay showed that winter extracts were more toxic and genotoxic than spring extracts. All the mutagenicity tests performed confirmed that urban air in North Italy in winter contains both volatile and non-volatile genotoxic substances able to induce genetic damage in bacteria, human cells and plants.

Polycyclic aromatic hydrocarbons within airborne particulate matter (PM(2.5)) produced DNA bulky stable adducts in a human lung cell coculture model

To extend current knowledge on the underlying mechanisms of air pollution particulate matter (PM(2.5))-induced human lung toxicity, the metabolic activation of polycyclic aromatic hydrocarbons (PAH) within PM(2.5) and PAH-DNA bulky stable adduct patterns in human alveolar macrophage (AM) and/or human lung epithelial L132 cells in mono- and cocultures were studied. In the coculture system, only human AM were exposed to air pollution PM(2.5), unlike L132 cells. Particles, inorganic fraction and positive controls [i.e. TiO(2), thermally desorbed PM (dPM) and benzo[a]pyrene, B[a]P, respectively] were included in the experimental design. Cytochrome P450 (CYP) 1A1 gene expression, CYP1A1 catalytic activity and PAH-DNA bulky stable adducts were studied after 24, 48 and/or 72 h. Relatively low doses of PAH within PM(2.5) induced CYP1A1 gene expression and CYP1A1 catalytic activity in human AM and, thereafter, PAH-DNA bulky stable adduct formation. Adduct spots in PM(2.5) -exposed human AM were higher than those in dPM-exposed ones, thereby showing the incomplete removal of PAH by thermal desorption. PAH within air pollution PM(2.5) induced CYP1A1 gene expression but not CYP1A1 catalytic activity in L132 cells. However, despite the absence of PAH-DNA bulky stable adduct in L132 cells from human AM/L132 cell cocultures exposed to dPM(2.5) or PM(2.5), reliable quantifiable PAH-DNA bulky stable adducts were observed in L132 cells from human AM/L132 cell coculture exposed to B[a]P. Taken together, these results support the exertion of genotoxicity of highly reactive B[a]P-derived metabolites produced within human AM not only in primary target human AM, but also in secondary target L132 cells.

Mutagenicity and genotoxicity of PM2.5 issued from an urbano-industrialized area of Dunkerque (France)

Epidemiological studies have demonstrated the link between chronic exposure to particulate matter (PM), especially particles with an aerodynamic diameter lesser than 2.5 µm (PM(2.5) ), and lung cancer. Mechanistic investigations focus on the contribution of the various genotoxicants adsorbed onto the particles, and more particularly on polycyclic aromatic hydrocarbons or nitroaromatics. Most of the previous studies dealing with genotoxic and/or mutagenic measurements were performed on organic extracts obtained from PM(2.5) collected in polluted areas. In contrast, we have evaluated genotoxic and mutagenic properties of urbano-industrial PM(2.5) (PM) collected in Dunkerque (France). Thermally desorbed PM(2.5) (dPM) was also comparatively studied. Suspensions of PM and dPM (5-50 µg per plate) were tested in Salmonella tester strains TA98, TA102 and YG1041 ± S9mix. Significant mutagenicity was observed for PM in YG1041 ± S9 mix. In strain TA102 - S9mix, a slight, but not significant dose-response increase was observed, for both PM and dPM. Genotoxic properties of PM and dPM were evaluated by the measurement of (1) 8-OHdG in A549 cells and (2) bulky DNA adducts on A549 cells and on human alveolar macrophages (AMs) in primary culture. A dose-dependant formation of 8-OHdG adducts was observed on A549 cells for PM and dPM, probably mainly attributed to the core of the particles. Bulky DNA adducts were observed only in AMs after exposure to PM and dPM. In conclusion, using relevant exposure models, suspension of PM(2.5) induces a combination of DNA-interaction mechanisms, which could contribute to the induction of lung cancer in exposed populations.

Physical-chemical and microbiological characterization, and mutagenic activity of airborne PM sampled in a biomass-fueled electrical production facility

Biomass combustion is used in heating and electric power generation in many areas of the world. Airborne particulate matter (PM) is released when biomass is brought to a facility, stored, and combusted. Occupational exposure to airborne PM within biomass-fueled facilities may lead to health problems. In March and August of 2006, airborne PM was collected from a biomass-fueled facility located in Denmark. In addition, source-specific PM was generated from straw and wood pellets using a rotating drum. The PM was analyzed for polycyclic aromatic hydrocarbons (PAHs), metals, microbial components, mutagenic activity, and ability to generate highly reactive oxygen species (hROS) in cell-free aqueous suspensions. PM collected from the boiler room and the biomass storage hall had higher levels of mutagenic activity, PAHs and metals, and a higher hROS generating potential than the source specific PM. The mutagenic activity was generally more potent without S9 activation, and on the metabolically enhanced strain YG1041, relative to TA98. Significant correlations were found between mutagenicity on YG1041 (without S9) and PAH concentration and mutagenicity on YG1041 (with S9) and hROS generating ability. PM collected in March was more toxic than PM collected in August. Overall, airborne PM collected from the facility, especially that from the boiler room, were more toxic than PM generated from straw and wood chips. The results suggest that exposure to combustion PM in a biomass-fueled facility, which likely includes PM from biomass combustion as well as internal combustion vehicles, may contribute to an elevated risk of adverse health effects.

Estimation of the contribution of ultrafine particles to lung deposition of particle-bound mutagens in the atmosphere

The present study was performed to estimate the contributions of fine and ultrafine particles to the lung deposition of particle-bound mutagens in the atmosphere. This is the first estimation of the respiratory deposition of atmospheric particle-bound mutagens. Direct and S9-mediated mutagenicity of size-fractionated particulate matter (PM) collected at roadside and suburban sites was determined by the Ames test using Salmonella typhimurium strain TA98. Regional deposition efficiencies in the human respiratory tract of direct and S9-mediated mutagens in each size fraction were calculated using the LUDEP computer-based model. The model calculations showed that about 95% of the lung deposition of inhaled mutagens is caused by fine particles for both roadside and suburban atmospheres. Importantly, ultrafine particles were shown to contribute to the deposition of mutagens in the alveolar region of the lung by as much as 29% (+S9) and 26% (-S9) for the roadside atmosphere and 11% (+S9) and 13% (-S9) for the suburban atmosphere, although ultrafine particles contribute very little to the PM mass concentration. These results indicated that ultrafine particles play an important role as carriers of mutagens into the lung.

A preliminary characterization of the mutagenicity of atmospheric particulate matter collected during sugar cane harvesting using the Salmonella/microsome microsuspension assay

During sugar cane harvesting season, which occurs from May to November of each year, the crops are burnt, cut, and transported to the mills. There are reports showing that mutagenic activity and PAH content increase during harvesting season in some areas of São Paulo State in comparison with nonharvesting periods. The objective of this work was to preliminarily characterize the mutagenic activity of the total organic extracts as well as corresponding organic fractions of airborne particulate matter (PM) collected twice from two cities, Araraquara (ARQ) and Piracicaba (PRB), during sugar cane harvesting season using the Salmonella/microsome microssuspension assay. One sample collected in São Paulo metropolitan area was also included. The mutagenicity of the total extracts ranged from 55 to 320 revertants per cubic meter without the addition of S9 and from not detected to 57 revertants per cubic meter in the presence of S9 in areas with sugar cane plantations. Of the three fractions analyzed, the most polar ones (nitro and oxy) were the most potent. A comparison of the response of TA98 with YG1041 and the increased potencies without S9 indicated that nitro compounds are causing the observed effect. More studies are necessary to verify the sources of the mutagenic activity such as burning of vegetal biomass and combustion of heavy duty vehicles used to transport the sugar cane to the mills. The Salmonella/microsome assay can be an important tool to monitor the atmosphere for mutagenicity during sugar cane harvesting season.

Woodsmoke health effects: a review

The sentiment that woodsmoke, being a natural substance, must be benign to humans is still sometimes heard. It is now well established, however, that wood-burning stoves and fireplaces as well as wildland and agricultural fires emit significant quantities of known health-damaging pollutants, including several carcinogenic compounds. Two of the principal gaseous pollutants in woodsmoke, CO and NOx, add to the atmospheric levels of these regulated gases emitted by other combustion sources. Health impacts of exposures to these gases and some of the other woodsmoke constituents (e.g., benzene) are well characterized in thousands of publications. As these gases are indistinguishable no matter where they come from, there is no urgent need to examine their particular health implications in woodsmoke. With this as the backdrop, this review approaches the issue of why woodsmoke may be a special case requiring separate health evaluation through two questions. The first question we address is whether woodsmoke should be regulated and/or managed separately, even though some of its separate constituents are already regulated in many jurisdictions. The second question we address is whether woodsmoke particles pose different levels of risk than other ambient particles of similar size. To address these two key questions, we examine several topics: the chemical and physical nature of woodsmoke; the exposures and epidemiology of smoke from wildland fires and agricultural burning, and related controlled human laboratory exposures to biomass smoke; the epidemiology of outdoor and indoor woodsmoke exposures from residential woodburning in developed countries; and the toxicology of woodsmoke, based on animal exposures and laboratory tests. In addition, a short summary of the exposures and health effects of biomass smoke in developing countries is provided as an additional line of evidence. In the concluding section, we return to the two key issues above to summarize (1) what is currently known about the health effects of inhaled woodsmoke at exposure levels experienced in developed countries, and (2) whether there exists sufficient reason to believe that woodsmoke particles are sufficiently different to warrant separate treatment from other regulated particles. In addition, we provide recommendations for additional woodsmoke research.

Genotoxicity of organic extracts of urban airborne particulate matter: an assessment within a personal exposure study

Airborne particulate matter, PM(10) and PM(2.5), are associated with a range of health effects including lung cancer. Their complex organic fraction contains genotoxic and carcinogenic compounds such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives. This study evaluates the genotoxicity of the PM(10) and PM(2.5) organic extracts that were sampled in the framework of a personal exposure study in three French metropolitan areas (Paris, Rouen and Strasbourg), using the comet assay, performed on HeLa S3 cells. In each city, 60-90 non-smoking volunteers composed of two groups of equal size (adults and children) carried the personal Harvard Chempass multi-pollutant sampler during 48h along two different seasons ('hot' and 'cold'). Volunteers were selected so as to live (home and work/school) in 3 different urban sectors contrasted in terms of air pollution within each city (one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment). Genotoxic effects are stronger for PM(2.5) extracts than for PM(10), and greater in winter than in summer. Fine particles collected by subjects living within the traffic proximity sector present the strongest genotoxic responses, especially in the Paris metropolitan area. This work confirms the genotoxic potency of particulate matter (PM(10) and PM(2.5)) organic extracts to which urban populations are exposed.

Toxicological assessment of ambient and traffic-related particulate matter: a review of recent studies

Particulate air pollution (PM) is an important environmental health risk factor for many different diseases. This is indicated by numerous epidemiological studies on associations between PM exposure and occurrence of acute respiratory infections, lung cancer and chronic respiratory and cardiovascular diseases. The biological mechanisms behind these associations are not fully understood, but the results of in vitro toxicological research have shown that PM induces several types of adverse cellular effects, including cytotoxicity, mutagenicity, DNA damage and stimulation of proinflammatory cytokine production. Because traffic is an important source of PM emission, it seems obvious that traffic intensity has an important impact on both quantitative and qualitative aspects of ambient PM, including its chemical, physical and toxicological characteristics. In this review, the results are summarized of the most recent studies investigating physical and chemical characteristics of ambient and traffic-related PM in relation to its toxicological activity. This evaluation shows that, in general, the smaller PM size fractions (<PM(10)) have the highest toxicity, contain higher concentrations of extractable organic matter (comprising a wide spectrum of chemical substances), and possess a relatively high radical-generating capacity. Also, associations between chemical characteristics and PM toxicity tend to be stronger for the smaller PM size fractions. Most importantly, traffic intensity does not always explain local differences in PM toxicity, and these differences are not necessarily related to PM mass concentrations. This implies that PM regulatory strategies should take PM-size fractions smaller than PM(10) into account. Therefore, future research should aim at establishing the relationship between toxicity of these smaller fractions in relation to their specific sources.

Analysis of mutagenic activity of airborne particulate matter, standard reference materials and reference compounds using base pair-specific Salmonella typhimurium tester strains

The mutagenicity profiles of organic extracts of airborne dust samples from Mannheim, Germany, and two standard reference materials (SRM) as well as eight compounds with different chemical properties were investigated using tester strains Salmonella typhimurium TA700x (Ames II Assay). Each strain of this series carries a unique missense mutation in the histidine operon and is reverted by only one specific base substitution out of six possible changes. Mutation patterns of eight compounds with different modes of genotoxic action reveal significant differences. Samples of airborne particulate matter (APM) from an industrialized town in Germany (Mannheim) were collected for five consecutive days once a month for 1 year using an automatic high-volume air sampler. Samples taken from Monday to Friday were Soxhlet-extracted and prepared according to standard methods. Although the threshold limit for the least active strains is not triggered by all samples, it can be concluded that mutation patterns of the samples do not vary between different seasons. Standard reference materials (SRMs) were prepared and tested using the same methods. SRMs and APM samples from Mannheim reveal similar mutagenicity profiles in TA700x strains. The comparison of the mutagenicity profiles of air dust extracts from Mannheim and the SRMs, respectively, with reference compounds investigated so far shows some similarities although the patterns do not fit perfectly. Mutagenicity profiles of TA700x-activity of nitro-aromatic compounds published so far are similar to those of APM collected in Mannheim, Germany, as well as to standard reference materials 1648 and 1649.

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.

Genotoxicity of PM10 and extracted organics collected in an industrial, urban and rural area in Flanders, Belgium

The variation in the genotoxic potency of PM10 in vitro in relation to the particle source type was investigated. Particles were collected at one urban, one rural, and one industrial site in Flanders. Genotoxicity was assessed using four different in vitro test systems exposed to PM10 in suspension and to the organic extracts of PM10. Two of these systems were bacterial assays: the Salmonella mutagenicity test and the Vitotox test. In addition, the Comet assay and Micronucleus test were performed using human blood cells. Results show that exposure to PM10 and the organic extracts from both urban and industrial areas causes significant genetic damage. The Salmonella mutagenicity test was most suitable for the screening of PM10 and the organic extracts; the Micronucleus test was most suitable only for the screening of organic extracts, and original particles were toxic for the exposed lymphocytes. Clear dose-response curves were not established in the Comet and Vitotox assay, and organic extracts were apparently toxic in the latter. The total polycyclic aromatic hydrocarbon content of the organic extracts, as measured with GC/MS, ranged between 1 and 6 ng/m3. Results obtained in this study suggest that PM10 causes DNA damage and mutations. The use of biological tests for the screening of air samples is useful to complement air quality control by chemical measurements.

Genotoxic and mutagenic activity of environmental air samples in Flanders, Belgium

Atmospheric pollution is assumed to play a role in the incidence of respiratory diseases and cancers. Airborne particles are able to penetrate deep into the lung and are composed of complex chemical mixtures, including mutagens and carcinogens such as polycyclic aromatic compounds (PACs). The present study reports mutagenic and genotoxic activities associated with ambient air collected near a busy street in Borgerhout, at an industrial site in Hoboken and in Peer, a rural community 70 km east of Antwerp in Flanders, Belgium. Airborne particulates (PM10) and semi-volatile organic compounds were sampled during winter and summer. Samples were collected with a high-volume sampler using quartz filters (QF) and polyurethane foam (PUF) cartridges. The mutagenic and genotoxic activity of the organic extracts was determined using the Salmonella test/standard plate-incorporation assay and the Vitotox assay. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC). The mutagenicity assay, using Salmonella typhimurium strain TA98, demonstrated direct mutagenicity of up to 58 revertants/m3 for the QF extracts and low or no mutagenic activity in the PUF extracts. Metabolic activation of the samples resulted in high indirect mutagenicity for both QF and PUF extracts: up to 96 revertants/m3 were found in QF samples and 62 revertants/m3 in PUF samples. Genotoxic effects of the filter extracts were assessed with the Vitotox assay: some direct genotoxic effects were noted, i.e. without metabolic activation, but almost no effects were observed after metabolic activation. Without activation, most PUF extracts were bacteriotoxic. With metabolic activation this toxicity disappeared, but genotoxic effects were not observed. Statistical analysis showed that the observed biological effects correlated well with the PAH concentrations.

Mutagenic activity as a parameter to assess ambient air quality for protection of the environment and human health

Atmospheric pollution has significant effects on maintaining the integrity of ecosystems and on the population's quality of life. Epidemiological studies have clearly associated related health problems, especially respiratory diseases, with exposure to air pollution. Organic compounds adsorbed to the airborne particulate matter are mutagenic in the Salmonella/microsome assay, and a considerable number of them are known to be carcinogenic to rodents. Studies performed at four sites within the urban area of Porto Alegre, capital of the state of Rio Grande do Sul, identified higher mutagenic activity at the sites with heavier vehicle traffic in assays without and with metabolic activation. The responses varied at different seasons of the year, and the highest revertants per cubic meter (rev/m(3)) values were observed in spring for moderately polar compounds, and in summer for non-polar ones. A pilot study was also performed in the region under the influence of a industrial petrochemical area. Most of the sites studied within the industrial area, as compared to others sampled in the nearby environment, presented higher levels of mutagenic activity independent of total suspended particulates (TSP) concentration in the sample. In the urban and industrial regions, the observed mutagenic activities were strongly associated with the presence of polycyclic aromatic hydrocarbons (PAHs). The responses observed in the TA98NR and TA98/1,8-DNP(6) strains suggest the activity of nitrocompounds in both studies. The Salmonella/microsome assay is a sensitive method to define areas contaminated by these compounds, even in samples with TSP values that are consistent with the legal environmental quality standards.

Mutagenic activity of airborne particulate matter as an indicative measure of atmospheric pollution

Mutagenic activity of organic extracts of airborne particulate matter at four different sites within the urban area of the city of Porto Alegre, Brazil, was investigated using the Salmonella/microsome assay, with the Kado microsuspension method. The extracts were obtained by sonication, sequentially extracted according to polarity, with cyclohexane (CX) and dichloromethane (DCM) solvents. The different fractions were tested for mutagenicity with the Salmonella typhimurium strains TA98, TA98NR and TA98/1,8-DNP6, without S9 mix metabolic activation. A positive frameshift mutagenic response was observed for non-polar (CX) and/or moderately polar (DCM) compounds at the different sites. The responses varied at different seasons of the year, and the highest revertants per m3 (rev/m3) values were observed at the site subject to the strongest influence of automotive vehicles (site 3) in spring (17.13 rev/m3) in DCM fractions, and in summer (13.01 rev/m3) in CX fractions. The responses observed for the TA98NR and TA98/1,8-DNP6 strains suggest the contribution of nitrocompounds to the mutagenic activity observed. Although there appears to be an indicative association between the increased mass per unit volume of air (TSP) and the mutagenicity of organic extracts of airborne particulate matter in the present study, the Salmonella/microsome assay was a sensitive method to define areas contaminated by genotoxic compounds, even in samples that present TPS values acceptable by the environmental quality standards established by law.