Molecular Compositions,\nMutagenicity, and Mutation\nSpectra of Atmospheric Oxidation Products of Alkenes and Dienes Initiated\nby NOx + UV or Ozone: A Structure–Activity Analysis

Photooxidation products resulting from volatile organic\ncompounds\n(VOCs) reacting with sunlight are important contributors to gas-phase\nair pollution. We characterized the product-weighted mutagenic potencies\n(rev m<sup>3</sup> mgC<sup>–1</sup> h<sup>–1</sup>)\nin <i>Salmonella</i> TA100 of atmospheres resulting from\nthe hydroxyl radical (OH)-initiated photochemical oxidation of 11\nC<sub>4</sub> or C<sub>5</sub> alkenes or dienes in the presence of\nnitric oxide (NO) and from the ozonolysis of four VOCs without NO\n(isoprene; 1,3-pentadiene; 1,4-pentadiene; and 1,3-butadiene). Irradiated\natmospheres from precursors with a single CC bond (3-methyl-1-butene,\n2-methyl-1-butene, <i>cis/trans</i>-2-pentene, 2-methyl-2-butene,\n1-butene, and 1-pentene) had low potencies (<5), whereas linear\ndienes with terminal CC bonds had high potencies (50–65).\nDienes with a branched structure (isoprene) or internal CC\nbonds (1,3-pentadiene) had intermediate potencies (15–20).\nNo VOCs were mutagenic without photochemical oxidation. VOCs+O<sub>3</sub> in the dark produced less mutagenic atmospheres than photochemistry\nin the presence of NO. Atmospheres induced primarily C to T and C\nto A mutations, the main base substitutions in nonsmoker lung cancer.\nAtmospheres from the photooxidation of isoprene and 1,3-pentadiene\nalso induced GG to TT, the signature mutation of peroxyacetyl nitrate.\nFive molecular compositions identified by Chemical Ionization Mass\nSpectrometry (CIMS), most containing nitrogen, correlated (<i>r</i> = 0.76–0.85) with the mutagenic potencies of irradiated\natmospheres; most had a likely nitrate functional group. Assessment\nof the mutagenicity of emitted VOCs should consider VOC photooxidation\nproducts, especially dienes with terminal CC bonds, as these\nproducts likely contribute to overall health effects from ambient\nair pollution.