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Abstract
Estimation of carcinogenic potency based on analysis of 16 polycyclic aromatic hydrocarbons (PAHs) ranked by U.S. Environmental Protection Agency (EPA) is the most popular approach within scientific and environmental air quality management communities. The majority of PAH monitoring projects have been focused on particle-bound PAHs, ignoring the contribution of gas-phase PAHs to the toxicity of PAH mixtures in air samples. In this study, we analyzed the results of 13 projects in which 88 PAHs in both gas and particle phases were collected from different sources (biomass burning, mining operation, and vehicle emissions), as well as in urban air. The aim was to investigate whether 16 particle-bound U.S. EPA priority PAHs adequately represented health risks of inhalation exposure to atmospheric PAH mixtures. PAH concentrations were converted to benzo(a)pyrene-equivalent (BaPeq) toxicity using the toxic equivalency factor (TEF) approach. TEFs of PAH compounds for which such data is not available were estimated using TEFs of close isomers. Total BaPeq toxicities (∑88BaPeq) of gas- and particle-phase PAHs were compared with BaPeq toxicities calculated for the 16 particle-phase EPA PAH (∑16EPABaPeq). The results showed that 16 EPA particle-bound PAHs underrepresented the carcinogenic potency on average by 85.6% relative to the total (gas and particle) BaPeq toxicity of 88 PAHs. Gas-phase PAHs, like methylnaphthalenes, may contribute up to 30% of ∑88BaPeq. Accounting for other individual non-EPA PAHs (i.e., benzo(e)pyrene) and gas-phase PAHs (i.e., naphthalene, 1- and 2-methylnaphthalene) will make the risk assessment of PAH-containing air samples significantly more accurate.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are widespread organic species in the environment, originating from a variety of sources including wild forest and peat fires [1,2,3], volcano emissions [4,5], and different biological processes [6,7]
(∑88 BaPeq), as well as with BaPeq toxicities that include gas-phase PAHs, the following ∑BaPeq ratios were calculated for each sample collected during the 13 projects considered here (Table S4): particulate matter (PM) ∑16 BaPeq
It should be noted that within each project there were BaPeq(%)I observations that were significantly lower than the project-average values. These results indicated that PAHs not included in the Environmental Protection Agency (EPA) priority list contributed more to the PM toxicity than the 16 EPA PAHs, especially in the case of heavy-duty vehicle emissions (E-projects, Table 1 and S4)
Summary
Polycyclic aromatic hydrocarbons (PAHs) are widespread organic species in the environment, originating from a variety of sources including wild forest and peat fires [1,2,3], volcano emissions [4,5], and different biological processes [6,7]. Atmospheric anthropogenic emissions of PAHs are mainly caused by the combustion of carbon-based fuels [6], such as fossil fuels [11,12,13,14], wood [15,16,17,18], peat [19], agricultural biomass [20,21,22,23], and animal waste [24,25,26]. Shen et al [29] showed that in 2007, global total atmospheric emission of the 16 U.S EPA priority. PAHs (16EPA PAHs) was 504 Gg, with biomass fuels combustion, mainly firewood and crop residues, contributing the most (approximately 60.5% of the total global PAH emissions). PAHs are of great environmental concern because of their widespread abundance [1,29,30,31,32,33] combined with high toxicity, Toxics 2017, 5, 17; doi:10.3390/toxics5030017 www.mdpi.com/journal/toxics
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