Atmospheric particle-bound polycyclic aromatic hydrocarbons, n-alkanes, hopanes, steranes and trace metals: PM2.5 source identification, individual and cumulative multi-pathway lifetime cancer risk assessment in the urban environment

The occurrence of atmospheric fine particles (PM_2.5)-associated polycyclic aromatic hydrocarbons (PAHs), trace metals and organic molecular markers was investigated by conducting an intensive sampling campaign at the Eastern Mediterranean urban area of Nicosia (Cyprus). Sixty-two 24-hr PM_2.5 samples were collected and analyzed for fifty parent and alkylated PAHs, twenty-five long chain n-alkanes, seventeen hopanes and twelve steranes used for source apportionment. The same number and kind of samples were analyzed to determine twenty-eight trace metals. Emphasis was given to investigate the air levels of the scarcely monitored although highly carcinogenic PAHs such as dibenzopyrenes, dibenzoanthracenes, 7H-benzo[c]fluorene and 5-methyl-chrysene, not included in the USEPA's sixteen PAH priority list (USEPA-16). UNMIX receptor model was applied to apportion the sources of atmospheric emissions of the determined organic compounds and trace metals and evaluate their daily contributions to the corresponding PM_2.5 associated concentrations. For comparison purposes, principal component analysis with multiple linear regression (PCA/MLR) was also applied and its results are reported. The UNMIX receptor model, compared to PCA/MLR, offered a more precise source profile and more reliable daily mass source distributions by eliminating negative contributions. The individual and cumulative multi-pathway lifetime cancer risk (posed via inhalation, ingestion and dermal contact) by exposure to PM_2.5-associated USEPA-16 listed and non-listed PAHs and selected airborne trace metals (As, Cd, Co, Ni, and Pb) were assessed. To estimate the contribution of each emission source to the total cancer risk, multiple linear regression analysis was performed, using as independent variables the daily source mass contributions and as dependent variables the respective cancer risk units. The estimated total cumulative cancer risk comprising all toxic PAHs, besides those included in the priority list, and metals was higher than the USEPA's threshold by a factor of eight, denoting a potential risk for long-term exposure of a population in the urban environment.

Environmental six-ring polycyclic aromatic hydrocarbons are potent inducers of the AhR-dependent signaling in human cells

The toxicities of many environmental polycyclic aromatic hydrocarbons (PAHs), in particular those of high-molecular-weight PAHs (with MW higher than 300), remain poorly characterized. The objective of this study was to evaluate the ability of selected environmentally relevant PAHs with MW 302 (MW302 PAHs) to activate the aryl hydrocarbon receptor (AhR), since this represents a major toxic mode of action of PAHs. A large number of the evaluated compounds exhibited strong AhR-mediated activities, in particular in human models. The studied MW302 PAHs also significantly contributed to the overall calculated AhR activities of complex environmental mixtures, including both defined standard reference materials and collected diesel exhaust particles. The high AhR-mediated activities of representative MW302 PAHs, e.g. naphtho[1,2-k]fluoranthene, corresponded with the modulation of expression of relevant AhR target genes in a human lung cell model, or with the AhR-dependent suppression of cell cycle progression/proliferation in estrogen-sensitive cells. This was in a marked contrast with the limited genotoxicity of the same compound(s). Given the substantial levels of the AhR-activating MW302 PAHs in combustion particles, it seems important to continue to investigate the toxic modes of action of this large group of PAHs associated with airborne particulate matter.

Distribution, toxicity, and origins of polycyclic aromatic hydrocarbons in soils in Ulsan, South Korea

This study was conducted to investigate the concentrations, distributions, toxicities, and sources of polycyclic aromatic hydrocarbons (PAHs) in the soils from different areas in Ulsan, South Korea. Samples were collected from 41 sites, including a waste treatment facilities area (WA), traffic facilities area (TA), child playground area (CA), industrial area (IA), railroad facilities area (RA), ore and iron scraps fields area (OA), and residential area (ReA). Ulsan was chosen for research area because it used to be an environmental hot spot in South Korea, and 16 PAHs in the US EPA priority pollutant list were selected. The concentration of total PAHs (t-PAHs) ranged from 61.7 to 12,421 μg/kg, and the average concentration of t-PAHs was 706.9 μg/kg. The distribution of PAHs by ring number indicated that the portion followed the order of 4 rings > 5 rings > 3 rings > 6 rings > 2 rings. According to PAH origin indices, LMW/HMW (low molecular weight 2-3 ring PAHs over high molecular weight 4-6-ring PAHs), phenanthrene/anthracene ratio and fluoranthene/pyrene ratio, benzo(g,h,i)perylene/indeno (1,2,3-c,d)pyrene ratio, vehicular emissions, and the combustion of fossil fuel were the sources of PAHs. The strong correlation (R² = 0.995) between t-PAHs and total carcinogenic PAHs (t-PAH_carc) indicated that the concentration of t-PAH_carc increased in proportion with that of t-PAHs. The toxic equivalent concentrations (TEQs) of PAHs in the soils ranged from 44.0 to 1929.9 μg TEQ/kg. It is imperative to set regulatory levels for PAHs for periodic monitoring and rapid remediation action of contaminated soils, because there are no national standards in South Korea for 15 PAHs with the exception of benzo(a)pyrene.

Vertical distribution, composition profiles, sources and toxicity assessment of PAH residues in the reclaimed mudflat sediments from the adjacent Thane Creek of Mumbai

A study on vertical distribution of magnetic susceptibility, carcinogenic and endocrine disrupting PAHs was performed in the reclaimed mudflat sediments adjacent to the Thane Creek of Mumbai. The 5-rings PAHs and ΣC-PAHs were more dominant at 120cm depth contributing 52.23% and 60.19% respectively to ∑PAHs. The average ratio values of LMW/HMW PAHs (0.58); Fla/(Fla+Pyr) (0.50); Ant/(Ant+Phe) (0.50); BaA/(Chry+BaA) (0.48); BaP/BghiP (2.06), Phe/Ant (1.03) and BaA/Chr (0.93) indicate that the PAH contamination might have raised due to inefficient combustion and pyrogenic emissions during the open burning of solid waste in the vicinity. This was further supported by the anthropogenic ferri(o)magnetic loading over the last 100years influencing the Creek sediments. The PAHs toxicity estimation was performed by calculating the toxic equivalent quantity (TEQ) value of 8.62ng TEQ/g which was below the safe level (600ng TEQ/g) suggested by the Canadian risk-based soil criterion for protection of human health.

Studies on polycyclic aromatic hydrocarbons in surface sediments of Mithi River near Mumbai, India: Assessment of sources, toxicity risk and biological impact

This study investigated the levels, sources and potential risks of 17 polycyclic aromatic hydrocarbons in surface sediment samples collected along the Mithi River of Mumbai. The concentration level of ΣPAHs found in the present study was in the range of 1206-4735 ng/g dw. The composition patterns of PAHs by ring size in sediment were surveyed which indicate the dominance of four rings followed by five and three ring PAHs. In the study it was observed that the high molecular weight PAHs (HMW PAHs) made greater contributions of 90.83% as compared to that of low molecular PAHs (LMW PAHs) contributing to 9.17% to the total PAH concentrations. Toxicity and biological risk were assessed using toxic equivalent quantity and sediment quality guideline quotient. It is feared that the pollution level of PAHs in the sediments might increase in coming times resulting in an unconspicuous risks for the environment and humans through food chains.