Assessment of Heavy Metal Content and Human Health Risk of Orogodo River, Delta State, Nigeria

The Orogodo River is a major source of water for drinking, cooking, bathing, fishing, washing and recreation for the resident community. Apparently, anthropogenic activities threaten the sustainability of this resource, hence, the need for environmental monitoring studies. This study was carried out to investigate heavy metal content and to assess human health risk of Orogodo River vis-a-vis its suitability for human consumption. Water samples were collected from four sampling stations established along the stretch of the river with the upstream station at Site 1, two midstream stations (Sites 2 and 3) and the downstream station being Site 4 and analyzed for seven heavy metals: iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), nickel (Ni), zinc (Zn) and lead (Pb) concentrations using the atomic absorption spectrophotometer. The results obtained from the study showed that the mean values for Fe (2.77±0.00 mg/l) in Site 4, Ni (0.15±0.19 mg/l) in Site 2, Pb (0.05±0.02 mg/l) in Site 3, Mn (0.30±0.30 mg/l) in Site 3 and Cr (0.06±0.03) in Sites 2 and 3 exceeded the Nigerian Standard for Drinking Water Quality (NSDWQ) maximum permissible limits (Fe: 0.3 mg/l; Ni: 0.02 mg/l; Pb: 0.01 mg/l; Mn: 0.2 mg/l and Cr: 0.05 mg/l) for Nigerian freshwater and thus warranted health risk assessment. Health risk assessment for all sites indicated that with exemptions of Cr (1.33 in Sites 2 and 3 for children), other metals showed no potential health risk, but their cumulative effects as indicated by the hazard index (1.19 and 2.50 for adult and children in Site 2; 1.22 and 2.91 for adult and children in Site 3 and 1.36 for children in Site 4) could be of serious concern. This calls for caution for both adults and children exposed to the water through ingestion and the dire need for enforcement of water resource management regulations by the concerned authorities.