Hazardous radical-coupled transformation products of benzophenone-3 formed during manganese dioxide treatment

Tsz-Ki Lam; Japhet Cheuk-Fung Law; Kelvin Sze-Yin Leung

doi:10.1016/j.scitotenv.2023.166481

Hazardous radical-coupled transformation products of benzophenone-3 formed during manganese dioxide treatment

Sci Total Environ. 2023 Nov 25:901:166481. doi: 10.1016/j.scitotenv.2023.166481. Epub 2023 Aug 22.

Authors

Tsz-Ki Lam¹, Japhet Cheuk-Fung Law¹, Kelvin Sze-Yin Leung²

Affiliations

¹ Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, P. R. China.
² Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, P. R. China; HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park, Shenzhen, P. R. China. Electronic address: s9362284@hkbu.edu.hk.

PMID: 37611723
DOI: 10.1016/j.scitotenv.2023.166481

Abstract

Radical-coupled transformation products (TPs) have been identified as the byproducts of various transformation processes, including both natural attenuation and artificial treatments, of phenolic micropollutants. Benzophenone-3 (BP-3), an organic UV filter of emerging concern, has been previously reported with ubiquitous occurrence in the natural environment and water bodies. Current research has demonstrated how TPs are formed from BP-3 when it is treated with manganese oxide (MnO₂). The ecological and toxicological risks of these TPs have also been assessed. Polymerization of BP-3 through radical coupling was observed as the major pathway by which BP-3 is transformed when treated with MnO₂. These radical-coupled TPs haven't shown further degradation after formation, suggesting their potential persistence once occurred in the environment. In silico experiments predict the radical-coupled TPs will increase in mobility, persistence and ecotoxicity. If true, they also represent an ever-increasing threat to the environment, ecosystems and, most immediately, aquatic living organisms. In addition, radical-coupled TPs produced by MnO₂ transformation of BP-3 have shown escalated estrogenic activity compared to the parent compound. This suggests that radical coupling amplifies the toxicological impacts of parent compound. These results provide strong evidence that radical-coupled TPs with larger molecular sizes are having potential adverse impacts on the ecosystem and biota.

Keywords: Estrogenic activity; In silico prediction; In vitro bioassay; MnO(2) transformation; Organic UV filters; Radical-coupled transformation products.