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DNA adducts induced by in vitro activation of extracts of diesel and biodiesel exhaust particles
Ross, J., G. Nelson, E. Mutlu, S. Warren, Ian Gilmour, AND D. DeMarini. DNA adducts induced by in vitro activation of extracts of diesel and biodiesel exhaust particles. INHALATION TOXICOLOGY. Informa Healthcare USA, New York, NY, 27(11):576-584, (2015).
Summary: This study examines the relative DNA adduction potential of exhaust particles produced when petroleum diesel, soy-based biodiesel, or petroleum diesel/biodiesel blend are combusted. The results indicated that the extractable organic material on each type of exhaust particle contains a variety of genotoxic species capable of forming DNA adducts, and that the DNA adducts formed correlate strongly with mutagenicity in Salmonella. Importantly, the lowest levels of DNA adduction potential were observed in particles from combustion of a 20% biodiesel:80% petroleum diesel blend, which is the typically available biodiesel fuel in the US. Why this study was performed: This research was conducted under Task 207, Relationships between the potency of different atmospheric smog mixtures on health; ACE Program Project NMP-1 The overall goal of this research task is to develop an integrated trans-disciplinary team encompassing expertise in fossil fuel combustion technology, atmospheric science and chemistry, climatology, and assessment of health and ecological effects to study the effects of atmospheric processing on source mixtures on adverse health risk. What is the impact to the field and the Agency? This study is the first to report DNA adduct emission factors that allow direct comparison of the relative genotoxic potential of petroleum diesel, biodiesel, and biodiesel/petroleum diesel blends on the basis of either mass of particulate produced or MJ of energy consumed. This study showed that both petroleum diesel and soy biodiesel emissions induced DNA damage in the form of presumptive PAH and nitro-PAH DNA adducts, and that such damage correlates with mutagenicity in Salmonella and is a key event in the initiation of chemical carcinogenesis by diesel exhausts. A 20% biodiesel/80% petroleum diesel blend , representative of the commercially available soy biodiesel fuel used commonly in the US, produced the lowest DNA adduct emission factor, which was approximately half that of petroleum diesel. This finding suggests that wider adoption of biodiesel may reduce the risk of adverse health effects mediated by the formation of DNA damage, including atherosclerosis and cancer.
AbstractContext: 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 32P-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 MJth energy consumed were B100 > B0 > B20. Conclusions: Soy biodiesel emissions induced DNA damage in the form of presumptive PAH and nitro-PAH DNA adducts, which 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.