Citation:

DeMarini, D. An Integrated View of Air Mutagenicity. Chinese Environmental Mutagen Society, Shanghai, N/A, CHINA, December 06 - 08, 2017.

Impact/Purpose:

There is only a limited understanding of the mutagenicity of the gas phase of polluted air, but those few studies have indicated that much of it is due to the secondary atmospheric transformation products produced by the action of sunlight on various organic contaminants in air. To examine this in a controlled setting, we generated 12 different atmospheres in a smog chamber containing UV lights to simulate solar irradiation and evaluated the mutagenicity of the gas phase of those atmospheres.

Description:

The mutagenic potency of ambient air particulate material (PM) in the Salmonella mutagenicity assay (revertants/mg PM) varies only ~1 order of magnitude worldwide; however, the mutagenic potency of the air itself (revertants/m3 of air) varies ~5 orders of magnitude (IARC Monograph Vol 109, 2016). Thus, the components and mutagenic potency of PM are somewhat similar worldwide, but the concentration of PM is highly variable. A similar situation may apply to the gas phase of ambient air—i.e., its components may be similar, but the concentrations of the components may vary among air sheds. To explore this, we generated 12 atmospheres in chambers containing UV lights simulating solar radiation and assessed their mutagenicity by exposing plates of Salmonella TA100 minus S9 at the air-agar interface. We produced individual atmospheres with 10 separate air pollutants, all but the last two of which are regulated by the U.S. EPA: benzene, ethylbenzene; toluene; o-, m-, and p-xylene; m-cresol; naphthalene; and 1,3,5- and 1,2,4-trimethylbenzene. We generated 2 atmospheres using complex mixtures: gasoline + α-pinene and gasoline + isoprene. None of the atmospheres were mutagenic without UV light. When the UV lights in the chamber were turned on, then 10 of the 12 atmospheres were direct-acting mutagens; m-cresol and naphthalene atmospheres were not mutagenic. The mutagenic potencies [rev/h/(mgC/m3)] varied less than one order of magnitude (5.7 fold, 2.0-11.4) and correlated (r > 0.8) with the concentrations of a selected few of 104 oxidized reaction products identified. The mutation spectrum of the gasoline atmospheres was 54% C → T and 46% C → A; ambient PM induces 26% C → T and 72% C → A. Reduced concentrations of ethylbenzene, a regulated pollutant, reduced the mutagenicity of the resulting atmosphere, which was due to secondary reaction products not typically measured or regulated. Thus, as with PM, the mutagenicity of the gas phase of ambient air may be composed of a group of atmospheric transformation products, and the variable mutagenicity of the gas phase of air may be due largely to the variable concentrations of those secondary reaction products and not to the presence of unique atmospheric transformation products among different air sheds. [Abstract does not reflect policies of the EPA.]

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