Long-Term Assessment of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) and Polychlorinated Biphenyls (PCBs) in the Ambient Air of Brescia, Northern Italy

From April 2015 through August 2022 levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were measured in ambient air (particulate and gas phases) at an urban site in Brescia, northern Italy. A total of 75 monthly samples (filter + PUF) were collected with a high volume sampler and analyzed using HRGC/HRMS. The total 2,3,7,8-substituted PCDD/F and dioxin-like PCB (dl-PCB) toxic equivalent (WHO2005-TEQ) concentrations ranged from 4.3 fg TEQ/m3 to 101.2 fg TEQ/m3 (average 18.7 fg TEQ/m3). The concentrations of PCDD/Fs and PCBs and the WHO2005-TEQ values were comparable to those reported in recent literature data for residential and moderately industrialized areas around the world. Only dl-PCB concentrations were higher than other urban locations. A clear seasonal variation was observed for monthly PCDD/F and WHO2005-TEQ concentrations, with higher levels in winter than in summer. No clear seasonality was observed for ΣPCBs while dl-PCBs showed higher concentrations in the warm season. In general, the homologue and congener profiles of PCDD/Fs and PCBs were quite similar throughout the seven years of study with limited seasonal differences. This suggests a constant influence of emission sources with time. PCDD/F concentrations were moderately correlated with other atmospheric pollutants (PM10, PM2.5, NO2, BaP). These correlations were not observed for PCBs. Evidence from the study suggests that the dominant source of PCBs in ambient air is re-evaporation from environmental reservoirs, while PCDD/Fs originate from current combustion-related sources. Principal component analysis showed that the profile of PCDD/Fs in ambient air is not comparable with the fingerprints of PCDD/F emissions from local steel mills (electric arc furnace, EAF).