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Mutagenic atmospheres resulting from the photooxidation of aromatic hydrocarbon and NOx mixtures
Riedel, T., D. DeMarini, S. Warren, E. Corse, J. Offenberg, Tad Kleindienst, M. Lewandowski, AND J. Zavala. Mutagenic atmospheres resulting from the photooxidation of aromatic hydrocarbon and NOx mixtures. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 178:164-172, (2018).
With the steady growth in global population and the associated rise in fossil fuel consumption and biomass burning, anthropogenic emissions of NOx (NO + NO2) and hydrocarbons (referred to synonymously as volatile organic compounds/carbon or VOCs) have increased over much of the past century. However, in recent decades, concentrations of VOCs and other criteria pollutants, such as ozone, NOx, SO2, and particulate matter (PM) have generally decreased in most developed countries due to technological developments and regulation.1-2 Likewise, even in rapidly developing countries such as China and India, concentrations of these criteria pollutants have generally stabilized or declined during the past decade, although episodes of extremely poor regional air quality are still frequent and receive global attention.
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 11.4 (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.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
EXPOSURE METHODS & MEASUREMENT DIVISION