Dibenzopyrenes,other PAHs with molecular weight 302, and selected carcinogenic PAHs seldom determined: identification and one-year quantification in urban air

The unambiguous identification in environmental samples of the potent carcinogen dibenzo[a,l]pyrene (DBalP) and the other DBPs (DBaeP, DBaiP, DBahP), whose evidence of carcinogenicity was recently re-evaluated by the International Agency for Research on Cancer (IARC), is an analytical challenge. This is attributed to their low concentrations in the environment and to the co-presence of several 302?MW isomers. In this study the four DBPs were identified in air, together with further four isomers with MW 302, based on an overall evaluation of five acceptance criteria. Their annual mean concentrations were quantified, for the first time to our knowledge. Thirteen other isomers were tentatively identified by comparison with previously published gas chromatographic profiles. The determinations were performed on PM10 samples collected every sixth day at a site in Rome, solvent extracted and analysed using GC/LRMS. The primary objective was to determine the mean DBP concentrations the population may be exposed to, and their consequent carcinogenic risks relative to benzo[a]pyrene (BaP) taken as a reference polycyclic aromatic hydrocarbon (PAH). The mean concentrations of DBalP, DBaeP, DBaiP and DBahP were, respectively, 0.014, 0.07, 0.02 and 0.01?ng?m^?3 (BaP: 0.65?ng?m^?3). Based on the available toxicity equivalence factors, DBalP contributed the carcinogenic risk of the PAH mixture by a factor of 2 relative to the risk attributable to BaP. DBaeP, DBahP and DBaiP contributed by, respectively, 11%, 1% and 0.3% of BaP. The instrumental conditions used to determine the 302?MW isomers allowed to unambiguously identify and to quantify other PAHs, ‘possibly carcinogenic’ to humans according to IARC, whose atmospheric concentrations reported in literature are scarce or missing: benzo[c]phenanthrene, 5-methylchrysene and benzo[j]fluoranthene (the latter being baseline resolved from isomers b and k). Finally, for completeness of information on PAHs recently upgraded by IARC to ‘possibly carcinogenic’, the concentrations of cyclopenta[cd]pyrene are reported.