Health implications of selected heavy metals around hydrocarbon impacted sites in the Niger Delta: A preliminary investigation

This study appraises the levels of Heavy metals and health implications in Khana and Gokana LGAs of Rivers State, Nigeria. A random sampling approach was employed for groundwater sampling and samples were collected from a total of twenty-two (22) boreholes in the area. A total of ten (10) residential boreholes were sampled in Khana LGA and twelve (12) in Gokana LGA. Iron (Fe) in Khana area showed concentration exceeding WHO and NSDWQ regulatory limits of 0.3mg/l in BH2, BH4, BH5, BH7, BH8, BH9 and BH10 while in Gokana area, BH11, BH12, BH14, BH17, BH19 and BH20 had Fe concentration exceeding the regulatory requirements. The result shows that Fe concentration in groundwater in the study area is significantly high to render the groundwater unsuitable for oral ingestion. Manganese concentration in samples from Khana showed concentrations above WHO standard in BH3, BH6 and BH9 while only BH16 exceeded the regulatory limit in Gokana area and then all other samples concentrations were within WHO regulatory limit for potable drinking water. Copper (Cu) and Lead (Pb) concentration showed levels below permissible limits in all samples analyzed. The results of hazard index from oral ingestion of water from boreholes in the area ranged from 0.30 to 1.13, with an average of 0.69. Based on USEPA classification, apart from BH9 and BH16 where harmful effect from groundwater consumption is recognized, there is no non-carcinogenic harmful effect that may arise from oral ingestion of most of the groundwater sources in the area. The spatial map revealed that the southern central area is a hot spot that needs urgent attention. The results of hazard index from dermal contact with groundwater in the area ranged from 0.02 to 0.36, with an average of 0.18. Carcinogenic health risk from oral ingestion of groundwater in the area ranged from 1.07 to 16.69, with an average of 8.69. Similarly, cancer risk from dermal contact with groundwater in the area ranged from 0.02 to 0.25 with an average of 0.13. Based on USEPA guidelines as revealed in this study, oral ingestion or dermal contact with groundwater from any borehole cited in Gokana and Khana areas are associated with possible cancer risk. The results and of this study will serve as a baseline data in the investigation of the suitability of groundwater in oil producing areas of Khana and Gokana LGAs of Rivers State for human consumption. Thus, the study has revealed the need of an urgent remediation of oil impacted areas in the study area to mitigate further impact on human health.