Positive Matrix Factorization reveals historical sources and combined environmental-biological transformation processes of organochlorine pesticides in Chrysichthys nigrodigitatus from the Calabar River: Implications for public health risks.

Organochlorine pesticides (OCPs) pose persistent threats to aquatic ecosystems and human health due to their bioaccumulative and toxic properties. This study assessed public health risks via oral ingestion of OCP, and revealed historical sources, oxidative degradation, and microbial dechlorination of OCPs. Sixty silver catfish (Chrysichthys nigrodigitatus) samples were collected from upstream (Marina Beach) and downstream (Nsidung Beach) stations, with OCPs analyzed via gas chromatography-electron capture detection. Total OCP concentrations were 3.35 ng g-1 (upstream) and 7.77 ng g-1 (downstream) ww, exceeding FAO/WHO limits for aldrin, endrin, dieldrin, heptachlor, DDT, and endrin ketone. Health risk assessments indicate that consumption of C. nigrodigitatus from the Calabar River poses negligible carcinogenic and non-carcinogenic risks for both adults and children. Positive Matrix Factorization (PMF) resolved four factors: Factor 1 (historical agricultural contamination from heptachlor, DDT, endosulfan I/II, dieldrin, endrin, and methoxychlor); Factor 2 (historical cyclodiene pesticide use); Factor 3 (recent endosulfan and endrin applications); and Factor 4 (historical combined cyclodiene, DDT, and methoxychlor use). These factors revealed combined environmental weathering and in vivo biotransformation processes, including oxidative degradation and dechlorination. Findings underscore the need for OCP monitoring and regulatory enforcement to safeguard public health in tropical river systems.