Mutagenic Atmospheres Generated from the Photooxidation of NO with Selected VOCs and a Complex Mixture: Apportionment of Aromatic Mutagenicity for Reacted Gasoline Vapor.

The interaction of sunlight with volatile organic compounds (VOCs) emitted from various sources results in mutagenic photooxidation products that contribute substantially to air pollution. Evaporation of gasoline is one such source of VOCs; however, no studies have evaluated the mutagenicity of the photooxidation products of gasoline vapors or of many of the non-aromatic constituent VOCs of gasoline. Here we determined the mutagenicity in TA100 of atmospheres generated in a steady-state atmospheric simulation chamber by irradiating gasoline and individual non-aromatic VOCs in the presence of nitrogen oxides (NO) in air. In addition to gasoline, we evaluated α-pinene; 2-pentene; ethanol; isobutanol; isoprene; and 2,2,4-trimethylpentane (isooctane). Cells were exposed at the air-agar interface to the atmospheres for 1, 2, 4, 8, or 16 h. Atmospheres generated in the dark were not mutagenic. However, under irradiation all atmospheres other than that of 2,2,4-trimethylpentane were mutagenic, with mutagenic potencies spanning 8.6-fold. The mutagenicity was due exclusively to direct-acting, late-generation photooxidation products. The non-aromatic VOCs studied here contributed little to the mutagenic potency of the photooxidation products of gasoline. However, the sum of the mutagenic potencies of these atmospheres plus those from the photooxidation of some aromatic VOCs in gasoline measured here and elsewhere (Riedel et al., Atmos Environ, 178:164, 2018) accounted for 71% of the mutagenic potency of the photooxidation products of gasoline vapor. In photochemical mixtures with strong biogenic contributions, isoprene products may also contribute significantly to mutagenic potency. Strategies to reduce the emissions of gasoline and those VOCs whose photooxidation products are most mutagenic would reduce VOC-associated air pollution and improve public health.