Passive air sampling networks combined with multivariate statistics reveal widespread non-Aroclor polychlorinated biphenyl sources to the Canadian atmosphere

Abstract

Polychlorinated biphenyls (PCBs) in the North American atmosphere were originally thought to arise through volatilization of commercial Aroclor mixtures, but there is growing evidence of atmospheric emissions of non-Aroclor, i.e., unintentionally produced, PCBs. Here, we report on measurements of all 209 PCB congeners in169 passive air samples collected between 2019 and 2022 using networks established around the Salish Sea, British Columbia (BC), and along the St. Lawrence River and Estuary, Quebec (QC), in Canada. Hierarchical cluster analysis and positive matrix factorization were employed to identify, distinguish, and quantify different PCB sources to the atmosphere. PCBs were detected at every single site, with elevated levels found in the urban centers of the region (Vancouver, BC; Montreal, Quebec City, QC), including in the vicinity of a municipal waste incinerator. We found evidence that suggests legacy Aroclor emissions, e.g., associated with electrical equipment storage in Pointe-Claire, QC, and building emissions in Burnaby, BC. We also identified several locations (e.g., in Sept-Îles and Alma, QC) where non-Aroclor sources are estimated to contribute over 40% of PCBs. In particular, PCB congeners 47, 51, and 68, known byproducts of 2,4-dichlorobenzoyl peroxide (2,4-DCBP) decomposition during silicone rubber and polyester production, were strongly associated with PCB-7 and -25. Although Aroclors were estimated to remain the main contributors of PCBs to the Canadian atmosphere, unintentional production is making a non-negligible contribution (estimated to be at least 10%). Of the known non-Aroclor sources, 2,4-DCBP is likely still used in North America with little to no regulation.