Non-carcinogenic and carcinogenic health risks associated with heavy metals and polycyclic aromatic hydrocarbons in well-water samples from an automobile junk market in Ibadan, SW-Nigeria

Unserviceable vehicles imported from developed countries are often dismantled in automobile junk markets and the useable parts sold. This generates hazardous waste oils which contain contaminants detrimental to the environment and human health. In this study, we quantified the potential human health risks associated with oral and dermal exposure to heavy metals and PAHs in well-water samples from a major automobile junk market in Ibadan, SW-Nigeria. Twenty-four to thirty-one water samples from seven wells within the market were analyzed for seven metals and eight PAHs using standard methods. Hazard-Quotient (HQ), Hazard-Index (HI), and Carcinogenic-Risk (CR) were computed for children and adults based on the USEPA Human-Health Risk Assessment model. Iron, Lead, Arsenic, Cadmium, Benzo(a)Anthracene, and Benzo(a)Pyrene exceeded regulatory limits. In children and adults, lead (1.14–3.71), cadmium (1.26–2.60) and arsenic (1.03–4.33) had HQ(ingestion) values exceeding 1. In addition, cadmium also posed risks via the dermal route in children in two of the seven sampled wells with an HQ of 1.76. Hazard Index was >1 via both routes in children (HI(ingestion):- 5.04–10.07; HI(dermal):- 1.12–2.12) but only via ingestion in adults (HI (ingestion):- 2.36–4.85). Well-3 samples posed the greatest non-carcinogenic risks via ingestion with HI values of 10.07 (children) and 4.85 (adults) respectively. Cadmium, arsenic, lead, and chromium could also elicit carcinogenic risk, with CR values of 1.00E − 02, 1.95E − 03, 1.11E − 04, and 3.30E − 04 which exceeded the 10(−4) limit indicating high risk, particularly in children. However, HQ and HI values for PAHs were <1 via both pathways suggesting no non-carcinogenic risk from PAH exposure. Carcinogenic risk estimates for Benzo(a)Anthracene (9.66E − 04) and Benzo(a)Pyrene (2.31E − 04) suggest moderate risks in exposed children via the dermal route. Adverse health effects including cancer may occur in the exposed population on prolonged usage of these polluted water sources. Urgent remediation measures are therefore necessary to protect the exposed population.