Investigation of carcinogenic and non-carcinogenic human health risk of heavy metals in spent synthetic-based drilling mud

This study conducted a broad risk assessment of the heavy metals present in spent synthetic- based drilling mud in the Niger Delta, Nigeria, particularly on evaluating their carcinogenic and non-carcinogenic effects on human health. Five samples drawn from five oil fields in the region were analyzed for their concentrations of heavy metals by the technique of atomic absorption spectroscopy. The results indicated that the concentration of majority of the heavy metals in the studied muds surpassed the permissible limits for disposal of the metals. Observed concentrations of the different heavy metals were used to calculate the health risk in children and as well as adults. While the Hazard Index (HI) for adults for various pathways was 0.26, indicating that non-carcinogenic effects of the metals in grownups were negligible, the non-carcinogenic effects in children habiting the oil producing villages showed to be severe as shown by the HI of 2.24- a value > 1. The same argument holds for progenies dwelling in areas where untreated spent drilling muds are disposed. 9.13E-05 and 5.29E-05, calculated as carcinogenic risk values for children and adults, respectively are within the permissible limits (1.00E-06 to 1.00E-04). While the results suggest for protective measures against non-carcinogenic effects to be provided for children exposed to used drilling mud, the study showed no evidence to support significant long-term cancer-related health concerns in either group.