Novel Nitro-PAH Formation from Heterogeneous Reactions of PAHs with NO₂, NO₃/N₂O₅, and OH Radicals: Prediction, Laboratory Studies, and Mutagenicity

Abstract

The heterogeneous reactions of benzo[a]pyrene-d12 (BaP-d12), benzo[k]fluoranthene-d12 (BkF-d12), benzo[ghi]perylene-d12 (BghiP-d12), dibenzo[a,i]pyrene-d14 (DaiP-d14), and dibenzo[a,l]pyrene (DalP) with NO2, NO3/N2O5, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono NO2-DaiP, and mono NO2-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions. NO2 and NO3/N2O5 were effective oxidizing agents in transforming PAHs to NPAHs, with BaP-d12 being the most readily nitrated. Reaction of BaP-d12, BkF-d12 and BghiP-d12 with NO2 and NO3/N2O5 resulted in the formation of more than one mono-nitro isomer product, while the reaction of DaiP-d14 and DalP resulted in the formation of only one mono-nitro isomer product. The direct-acting mutagenicity increased the most after NO3/N2O5 exposure, particularly for BkF-d12 in which di-NO2-BkF-d10 isomers were measured. The deuterium isotope effect study suggested that substitution of deuterium for hydrogen lowered both the direct and indirect acting mutagenicity of NPAHs and may result in an underestimation of the mutagencity of the novel NPAHs identified in this study.

Global long-range transport and lung cancer risk from polycyclic aromatic hydrocarbons shielded by coatings of organic aerosol

“…Previous modeling studies have primarily assumed that PAHs that undergo heterogeneous oxidation in the atmosphere are completely degraded (11,21,38). However, recent experimental studies show that several oxidized PAHs could remain particle-bound, and often appear as higher molecular weight peaks in particle mass spectra (25,39). Some oxidized BaP species have been shown to be toxic (40), and some are direct-acting mutagens (39); therefore, it is important to quantify their atmospheric exposure.…”

Identification and Toxicological Evaluation of Unsubstituted PAHs and Novel PAH Derivatives in Pavement Sealcoat Products

“…Jariyasopit et al previously showed that 1-NP was formed on ambient particulate matter after direct exposure to NO 3 /N 2 O 5 and OH radical. 21,29 OPAHs, such as 9-FLU and ANQ, have also been observed to form on ambient particulate matter as the product of atmospheric reaction. 41–43 This suggests the increased concentrations of some NPAHs and OPAHs on the sealcoated surface over time may have originated, in part, from phototransformation of unsubstituted PAHs and MPAHs 19,44,45 on sealcoated surface.…”

“…27 Salmonella strain TA98 (Xenometrix Inc., Allschwil, Switzerland) was used, in combination with the rat S9 mix, to test the mutagenicity, with and without metabolic activation, as previously described. 19,28,29 2-aminoanthracene and 4-nitro-1,2-phenylenediamine were used as positive controls for with and without rat S9 mix, respectively. DMSO was used as the negative control for both experimental conditions.…”

Heterogeneous Reactions of Particulate Matter-Bound PAHs and NPAHs with NO3/N2O5, OH Radicals, and O3 under Simulated Long-Range Atmospheric Transport Conditions: Reactivity and Mutagenicity

“…36,41 The major NPAH isomers formed by heterogeneous nitration have the NO 2 group added to the highest electron density position. 31 The radical-initiated reactions of FLA and PYR are expected to follow a different mechanism where the OH or NO 3 radical attacks FLA or PYR at the highest electron density position, followed by NO 2 addition at the ortho position and subsequent loss of H 2 O or HNO 3 , yielding 2-NF and 2-NP as the major NPAH products. 33,36,44,45 In addition, the N 2 O 5 concentration and the N 2 O 5 /NO 2 ratio in the photochemical chamber during our NO 3 /N 2 O 5 exposure experiments were at least 2 orders of magnitude higher than the average ambient concentration, 33 suggesting a higher potential for heterogeneous reactions with N 2 O 5 .…”