Evaluation of an Air Quality Health Index for Predicting the Mutagenicity of Simulated Atmospheres
Citation:
Zavala-Mendez, J., J. Krug, S. Warren, Todd Krantz, C. King, J. Mckee, S. Gavett, M. Lewandowski, W. Lonneman, T. Kleindienst, M. Meier, M. Higuchi, M. Ian Gilmour, AND D. DeMarini. Evaluation of an Air Quality Health Index for Predicting the Mutagenicity of Simulated Atmospheres. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 52(5):3045–3053, (2018).
Impact/Purpose:
The concentrations of chemical species that can lead to smog formation and air quality events are controlled by the U.S. EPA under the Clean Air Act (2015 U.S. Code, Title 42, Chapter 85). NO2 is regulated under the National Ambient Air Quality Standards (NAAQS), and many volatile organic compounds (VOCs) are labeled as hazardous air pollutants due to adverse health effects. The pollutants in air occur bound to particles (particulate matter or PM) or else can be as volatile or semi-volatile gases. The International Agency for Research on Cancer (IARC) has evaluated PM as a known (Group 1) human lung carcinogen, and there are hundreds of studies of more than 2300 air samples showing the mutagenicity of organic extracts of PM (IARC, Vol. 109, 2016). However, there are only approximately 15 studies on the mutagenicity of the gas phase of air, and only ~6 in which the mutagenicity of the gas phase of simulated atmospheres (generated in a smog chamber) were reported. The present study evaluated two simulated atmospheres (SAs) created in a smog chamber that had similar Air Quality Health Indexes (AQHI), but where the organics in one atmosphere were largely on the particles (SA-PM) and the other where most were in the gas phase (SA-O3). Although the mutagenic potency of SA-O3 was 3 times greater than that of SA-PM, the mutation spectra were similar (approximately 50% G to T and 50% G to A). Thus, it appears that the gas phase of atmospheres with similar AQHI values but with dissimilar proportions of organics partitioned between the particulate and gas phase, may have gas phases with somewhat similar mutagenicities. Thus, an AQHI may be somewhat predictive of the mutagenicity of the gas phase of polluted air. Such results would have relevance to the Clean Air Act and to application of controls on air pollution using an AQHI.
Description:
No study has evaluated the mutagenicity of atmospheres with a calculated air quality health index (AQHI). Thus, we generated in a UV-light-containing reaction chamber two simulated atmospheres (SAs) with similar AQHIs but different proportions of criteria pollutants and evaluated them for mutagenicity in three Salmonella strains at the air-agar interface. We continuously injected into the chamber gasoline, nitric oxide, and ammonium sulfate, as well as either α-pinene to produce SA-PM, which had a high concentration of particulate matter (PM): 119 ppb ozone (O3), 321 ppb NO2, and 1007 μg/m3 PM2.5; or isoprene to produce SA-O3, which had a high ozone (O3) concentration: 415 ppb O3, 633 ppb NO2, and 55 μg/m3 PM2.5. Neither PM2.5 extracts, NO2, or O3 alone, nor nonphoto-oxidized mixtures were mutagenic or cytotoxic. Both photo-oxidized atmospheres were largely direct-acting base-substitution mutagens with similar mutagenic potencies in TA100 and TA104. The mutagenic potencies [(revertants/h)/(mgC/m3)] of SA-PM (4.3 ± 0.4) and SA-O3 (9.5 ± 1.3) in TA100 were significantly different (P < 0.0001), but the mutation spectra were not (P = 0.16), being ∼54% C → T and ∼46% C → A. Thus, the AQHI may have some predictive value for the mutagenicity of the gas phase of air.
