Supplementary material to "Nation wide increase of polycyclic aromatic hydrocarbons in ultrafine particles during winter over China"

Abstract. Polycyclic aromatic hydrocarbons (PAHs) are toxic compounds in the atmosphere and have adverse effects on public health, especially through the inhalation of particulate matter (PM). At present, there are limited understandings in size distribution of particulate-bound PAHs and its health risk on a continental scale. In this study, we carried out a one-year PM campaign and simultaneously measured size-segregated PAHs at 12 sites across six regions of China. The annual averages of total 24 PAHs (∑24PAHs) and benzo[a]pyrene (BaP) carcinogenic equivalent concentration (BaPeq) ranged from 7.56 to 205 ng m−3 with a mean of 53.5 ng m−3 and 0.21 to 22.2 ng m−3 with a mean of 5.02 ng m−3, respectively. At all the sites, ∑24PAHs and BaPeq were dominated in the ultrafine particles with aerodynamic diameter 3.3 µm. Compared with the southern China, the northern China witnessed much higher ∑24PAHs (87.36 ng m−3 vs. 17.56 ng m−3), BaPeq (8.48 ng m−3 vs. 1.34 ng m−3) and PAHs inhalation cancer risk (7.4 × 10−4 vs. 1.2 × 10−4). Nationwide increases in both PAH levels and inhalation cancer risk occurred in winter. The unfavorable meteorological conditions and enhanced emissions of coal combustion and biomass burning together led to severe PAHs pollution and high cancer risk in the atmosphere of the northern China, especially during winter. Our results suggested that the reduction of coal and biofuel consumption in the residential sector could be crucial and effective to lower PAH concentrations and its inhalation cancer risk in China.