Human health risks from multi-metal exposure via fish consumption in urban markets of southwestern Nigeria

Heavy metal contamination in fish cause a great public health concern as a result of its potential to bio-accumulate and its chronic exposure via diet, also because it is the major source of protein in low and middle income countries globally. This aim of this study was to critically assess the human health risks linked with a plethora of heavy metals via consumption of two popularly consumed fish; hake and herring ( Merluccius merluccius and Clupea harengus ) sold at four selected urban markets in Ado Ekiti. The Fish was obtained once a month from four popular urban markets in Ado-Ekiti (Nigeria) for a 12 months period and assayed for arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), manganese (Mn), lead (Pb), and nickel (Ni) via atomic absorption spectrophotometry (AAS). Potential human health risk assessments (non-carcinogenic and carcinogenic) were assessed using hazard quotient (HQ), hazard index (HI), and cancer risk (CR) models. Our findings showed spatial and temporal variations in metal associated risks across sampling months, fish species and markets. Although, a lot of the HQ values fell below the safety threshold of 1.0, elevated HQs were observed for Pb, Cd, and As in specific markets and months, particularly during the dry season. Furthermore, the HQ values demonstrated variation across the metals, markets and fish ranging from < 0.01 for Co, Mn, and Ni to peak values exceeding 2.0 for Pb, Cd, and As in in precise markets and months. The annual HI exceeded the safety limit of 1 for hake (1.58) and herring (1.67). The juxtaposed non-carcinogenic risk (HI) exceeded the threshold (HI > 1) for hake and herring, with higher risk levels consistently recorded for herring compared to hake. Market-specific analysis revealed Market 2 and Market 4 as a location of very much high exposure risk and carcinogenic risk assessment showed that As and Cd were the major donors to total risk of cancer, with a plethora of values exceeding the acceptable range (1 × 10 − 4 ), especially in the month February. Taken together the result from this study sheds light on the possible long-term health risks linked with fish consumption in Ado Ekiti and underscore the important for stringent monitoring, improved food safety regulation, and targeted public health interventions to mitigate metal exposure through dietary pathways.