The concentrations of subgroups of PAH in the collected samples presented together with the respective PM-induced IL-6 from alveolar rat macrophages after exposure to 20 μg/ml of coarse (C) and fine (F) fraction collected in Oslo, Rome, Lodz and Amsterdam in spring (upper), summer (middle) and winter (lower) seasons. IL-6 release is shown on the left ordinate, values in the diagram are mean ± SEM (n = 3). Concentration of PAH are shown on the right ordinate (ng/mg PM). Values of the subgroup of PAH representing emissions from combustion of diesel are the summarised concentrations of phenantrene, 1-methylphenantrene, fluoranthene and pyrene in each PM-sample. Values of the subgroup of PAH representing emissions from gasoline engines and wood burning are the summarised concentrations of naphthalene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[g,h,i]perylene in each sample. Values of other PAH represent the sum of acenaphthene and benzo[a]pyrene in each sample.