Atmospheric assessment of polychlorinated naphthalenes (PCNs) and polychlorinated biphenyls (PCBs) using pine needles...

Polychlorinated naphthalenes (PCNs) and polychlorinated biphenyls (PCBs), once widely used for their desirable insulating properties and chemical stability, are now banned due to their toxicity and persistence. In this study, pine needle samples were collected in March 2024 at 25 sites in residential, industrial, and scrap processing areas in Detroit, Michigan and analyzed for 32 PCN congeners and 37 PCB congeners to assess contamination levels, spatial distribution, homologue profiles, potential emission sources and health risks. The geometric mean concentrations of Σ₃₂PCNs and Σ₃₇PCBs were 13.0 ng/g and 354 ng/g, respectively. Tri-, penta-, and hepta-CNs were the predominant PCN homologues, and tri-CB was the dominant PCB. Despite international bans and short atmospheric half-lives, these concentrations, which exceeded levels reported in most other countries, suggest ongoing releases. Spatial differences in composition suggest source-specific contamination rather than legacy sources like the Halowaxes, which was reinforced by principal component analyses indicating that PCNs likely originated from thermal processes such as refining, coal and wood combustion, while PCBs were linked to metal scrap facilities handling waste oils. Elevated levels were found in both industrial and adjacent residential areas. The toxic equivalency of PCNs was 141 times higher than that of PCBs, suggesting that PCNs had greater potential for greater health risk than PCBs. To our knowledge, this is the first study to investigate atmospheric PCNs in Detroit, and our findings indicate the need for further assessment and potentially mitigation to reduce exposures and risks associated with these persistent organic pollutants.