CARCINOGENIC

Mining and quarrying activities significantly contribute to environmental degradation and heavy metal contamination in Nigeria. The mechanical extraction of mineral resources leads to extensive landscape degradation, soil contamination, and increased human exposure to toxic elements. The study evaluated the carcinogenic and non-carcinogenic health risks associated with heavy metal contamination in soils surrounding quarrying communities in Ikpeshi and its environs, Edo State, Nigeria; assessing the extent of pollution, the ecological risk posed by heavy metals, and their potential human health implications. Soil samples were collected from four different locations at varying distances (0m, 100m, 200m) from active quarrying sites. Heavy metal concentrations were analyzed using Atomic Absorption Spectrophotometry (AAS). Pollution indices, including the Contamination Factor (Cf), Pollution Load Index (PLI), and Geo-accumulation Index (Igeo), were used to assess contamination levels. Human health risk assessments followed the United States Environmental Protection Agency (USEPA) guidelines, computing the Average Daily Dose (ADD), Hazard Quotient (HQ), and Total Carcinogenic Risk (TCR) for ingestion, dermal contact, and inhalation exposure. The findings revealed that iron (Fe) had the highest concentration, with a mean value of 412.884 mg/kg. Followed by zinc (Zn) with a mean concentration of 40.652 mg/kg. Copper (Cu) (28.348 mg/kg). Lead (Pb) (1.105–5.755 mg/kg), cadmium (Cd) (0.5–2.01 mg/kg), nickel (Ni) (6.86–18.41 mg/kg), and chromium (Cr) (5.16–12.075 mg/kg) were also detected, with Cd and Ni exceeding permissible limits. The Pollution Load Index (PLI > 1) and Geo-accumulation Index (Igeo > 1) indicated moderate to heavy contamination in soils near quarry sites. The non-carcinogenic risk assessment showed that children had a higher cumulative Hazard Index (HI = 0.13745) than adults (HI = 0.02417), suggesting increased vulnerability. For dermal exposure, cobalt (Co) had the highest HQ (0.03526) in children, indicating potential health risks. Carcinogenic risk assessment showed that nickel (Ni) (TCR = 2.14 × 10⁻⁴ for children, 3.10 × 10⁻⁵ for adults) and chromium (Cr) (TCR = 4.61 × 10⁻⁵ for children, 6.68 × 10⁻⁶ for adults) posed potential long-term cancer risks, exceeding the safe threshold (10⁻⁶) set by USEPA. Lead (Pb) and cadmium (Cd) had relatively lower carcinogenic risks, but their cumulative exposure remains a concern. The results reveal significant heavy metal contamination in quarrying communities, with potential long-term health consequences, particularly for children.

This study evaluated the non-carcinogenic health risks associated with dermal exposure to heavy metals chromium (Cr), lead (Pb) and zinc (Zn) in groundwater from Ikpeshi, Edo State, Nigeria. The research aimed to quantify metal concentrations, assess health risks across population groups, identify contamination sources and propose mitigation strategies. Groundwater samples were analyzed and risk assessment models were applied using Chronic Daily Intake (CDI), Hazard Quotient (HQ) and Hazard Index (HI) frameworks as outlined by the United States Environmental Protection Agency (USEPA, 2004). Results revealed that chromium exhibited the highest mean concentration (0.177 mg/L), followed by zinc (0.257 mg/L) and lead (0.016 mg/L). Both Cr and Pb levels exceeded the permissible limits set by the World Health Organization (WHO, 2017) and USEPA, primarily due to artisanal and small-scale mining, mine tailings leaching and oxidation of metal-bearing minerals within the Igarra schist belt. Risk assessment outcomes indicated that children are more vulnerable to dermal exposure than adults, given their higher skin surface area-to-body weight ratio and frequent water contact. Chromium was identified as the dominant contributor to non-carcinogenic risks, followed by lead, while zinc showed minimal contribution. Some HI values for children exceeded unity, indicating potential chronic health effects and the mean carcinogenic risk (CR) for Cr approached the USEPA threshold of 1 × 10⁻⁴. The study concludes that chromium and lead pose significant public health concerns in Ikpeshi groundwater. The findings emphasize the need for effective groundwater monitoring, regulation of mining effluents and community-based mitigation strategies such as the use of affordable household filtration systems, rainwater harvesting and public health education to reduce dermal exposure risks and safeguard water quality.