Citation:

Zavala, J., T. Riedel, M. Lewandowski, J. Krug, S. Warren, Todd Krantz, C. King, S. Gavett, Bill Lonneman, Tad Kleindienst, M. Meier, M. Higuchi, Ian Gilmour, AND D. DeMarini. The Concentrations but Not the Components of Particulate Material and Atmospheric Transformation Products May Account for Much of the Variation in Air Mutagenicity. Environmental and Molecular Mutagenesis Society, Raleigh, NC, September 09 - 13, 2017.

Impact/Purpose:

This study used a smog chamber to demonstrate that the mutagenicity of the gas phase of air is due largely to atmospheric transformation products produced by the action of UV light from the sun on various aromatic compounds in the air. The study showed that without the UV light, atmospheres containing any of 10 aromatic compounds, nearly all of which are regulated by the U.S. EPA in ambient air, were not mutagenic. However, with the UV lights on (to simulate the sun), 8 out of the 10 atmospheres were mutagenic. Thus, the mutagenicity of the gas phase of ambient air is due largely to the formation of atmospheric transformation products, almost none of which are monitored or regulated. However, the study also showed that reducing the concentration of the regulated, primary aromatic compound reduced the mutagenicity of the resulting smog atmosphere. Thus, regulating primary air pollutants as is currently done, likely regulates the formation of atmospheric transformation products, which are the compounds responsible for much of the mutagenicity of ambient air.

Description:

The mutagenic potency of ambient air particulate matter (PM) in Salmonella (rev/mg PM) varies ~2 orders of magnitude worldwide; however, the mutagenic potency of the air (rev/m3 of air) varies ~5 orders of magnitude (IARC Monograph Vol 109, 2016). To explore if a similar situation applies to the gas phase of air pollution, we generated 12 atmospheres in chambers containing UV lights simulating solar radiation and assessed their mutagenicity by exposing plates of Salmonella TA100 -S9 at the air-agar interface. We produced individual atmospheres with 10 air pollutants: benzene, ethylbenzene; 1,3,5- and 1,2,4-trimethylbenzene; toluene; o-, m-, and p-xylene; m-cresol; and naphthalene. We generated 2 atmospheres using complex mixtures: gasoline + α-pinene and gasoline + isoprene. Ten atmospheres were direct-acting mutagens and required UV irradiation; m-cresol and naphthalene atmospheres were not mutagenic. The mutagenic potencies [rev/h/(mgC/m3)] varied less than one order of magnitude (5.2 fold, 2.0-10.4) and correlated (r > 0.8) with the concentrations of a selected few of 104 oxidized reaction products identified. The average mutation spectrum of the gasoline atmospheres was 54% C → T and 46% C → A; ambient PM induces 26% C → T and 72% C → A. The mutagenicity of the gas phase of these atmospheres was due entirely to atmospheric transformation products, which typically are not monitored or regulated directly. As with PM, the mutagenicity of the gas phase may be due to a similar mix of organics whose concentrations vary among air sheds. [Abstract does not reflect policies of the EPA.]

Record Details: