Occurrence of fungal contaminants and polychlorinated biphenyls in coastal groundwater of Ondo State, Nigeria: implications for water quality

Access to safe drinking water remains a challenge in many rural coastal communities. This study assessed fungal contaminants and polychlorinated biphenyls (PCBs) in groundwater from coastal Ondo State, Nigeria, and evaluated associated public health risks. Using culture-based methods and GC-MS analysis, twelve fungal isolates across eight genera, including Aspergillus, Fusarium, and Penicillium, known for mycotoxin production were detected. Among the fungi, Rhodotorula and Rhizopus had the highest percentage occurrence of 77.8 and 66.7% respectively. Eighteen PCB congeners were quantified, with individual congener concentrations ranging from below the detection limit to 3.90 ng/L (PCB18); the corresponding total (ΣPCB) concentration is reported in the main text. Low-chlorinated homologues (Di- and Tri-PCBs) dominated the congener profile. All PCB concentrations remained below the US EPA Maximum Contaminant Level of 500 ng/L for total PCBs. Corrected non-carcinogenic health risk assessments revealed that hazard quotients for all assessed congeners remained below the threshold of 1.0, indicating that modelled non-carcinogenic risks are within acceptable limits; carcinogenic risk was not evaluated because the required congeners were not determined. Nevertheless, the occurrence of fungal genera at colony counts exceeding commonly cited but non-regulatory reference values warrants further microbiological monitoring; fungal pathogenicity, toxin production and health outcomes were not directly assessed in this study. These findings highlight the need for integrated monitoring of microbial and chemical contaminants in coastal groundwater systems and further investigation to inform targeted interventions to protect community health. First reported integrated assessment of fungal genera and PCBs in coastal groundwater of Ondo State. Twelve fungal isolates across eight genera detected including mycotoxin-producing Aspergillus and Fusarium. Eighteen PCB congeners identified with concentrations remaining below US EPA guidelines. Low-chlorinated PCB homologues (Di- and Tri-PCBs) dominated the congener profile. Corrected risk assessments indicate non-carcinogenic hazard quotients are within acceptable limits.