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MUTAGENICITY AND DNA ADDUCT FORMATION OF PAH, NITRO-PAH, AND OXY-PAH FRACTIONS OF ATMOSPHERIC PARTICULATE MATTER FROM SAO PAULO, BRAZIL
Citation:
UMBUZEIRO, G., A. FRANCO, M. H. MARTINS, F. KUMMROW, L. CARVALHO, H. H. SCHMEISER, J. LEYKAUF, M. STIBOROVA, AND L. D. CLAXTON. MUTAGENICITY AND DNA ADDUCT FORMATION OF PAH, NITRO-PAH, AND OXY-PAH FRACTIONS OF ATMOSPHERIC PARTICULATE MATTER FROM SAO PAULO, BRAZIL. MUTATION RESEARCH. Elsevier Science Ltd, New York, NY, 652(1):72-80, (2008).
Impact/Purpose:
We wanted to ascertain the level of genotoxicity responses contributable to emissions taken immediately next to a heavily traveled road and a near roadway site.
Description:
Summary
What is the study?
Near roadway and immediate roadway exposures to transportation emissions gave very similar results in the Salmonella mutagenicity assay and in an assay for DNA adducts indicating that near roadway genotoxicity is not altered significantly over short distances.
Why was it done?
The potential health effects of near roadway exposures to transportation emissions is an emerging concern in many countries. Previous efforts had shown that diesel and other automotive emissions were mutagenic and also had shown that atmospheric transformation altered the mutagenicity. Because Brazil has a high use of ethanol and diesel fuels as the U.S. and other countries may have in the future, we wanted to ascertain the level of genotoxicity responses contributable to emissions taken immediately next to a heavily traveled road and a near roadway site.
What is the impact to the field and the agency?
The organic matter from the airborne particles provided testable amounts of PAH, Nitro-PAH, and Oxy-PAH fractions for mutation analysis and for examining DNA adducts. The PAH fraction from both sites showed negligible Salmonella mutagenic activity. The highest mutagenic activity was found for the Nitro-PAH fraction; however, results were comparable for both sites. Also, DNA adduct levels were not significantly different between the sampling sites. 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.
Abstract
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 were 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 the 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 108 normal nucleotides. In contrast, the DNA binding of reductively-activated Oxy-PAH fractions was 3 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.
