Application of Assessment Models for Health Risk and Pollution From Surface Water From Okumpi River in Nwangele, Imo State, Nigeria

Abstract The study targets at examining the pollution assessment and environmental health effects of surface water from Okumpi River. Ten surface water samples were collected randomly both in wet and dry seasons within the river that was assessed. The models used for assessment include contamination factor (Cf), pollution load index (PLI), water quality index, dermal and absorption exposure dose, hazard quotient (HQ), hazard index (HI) and carcinogenic risk (CR). The mean and standard deviation pH value in the present study during the wet and dry seasons varied from 6.21±0.22 - 5.75±0.41. The mean and standard deviation EC in the current study ranges between 219.15±12.20 - 193.30±14.81 μS/cm for wet and dry seasons which are found to be in line with the WHO standard used. The mean and standard deviation of DO for this study during the wet and dry seasons were found to be 10.03±0.58 - 6.47±0.41 (mg/L). TDS for wet and dry seasons ranges from 374.79±5.33 - 121.65±6.33 mg/L. The colour of the water samples at both seasons were lower than the permissible limit 9.60±0.89 - 11.20±3.11 PCU against 15 PCU used as the standard. The nitrate [9.05±1.08 - 8.09±1.57], sulphate [3.91±0.51 - 3.73±0.46] and phosphate [82.78±3.86 - 81.76±3.32] in this present study for wet and dry season were all found to be below the standard of WHO for safe drinking water. Among all the heavy metals studied, Iron [1.28±0.01 - 0.37±0.01 (mg/L)] and Nickel [0.98±0.04 - 1.03±0.04 (mg/L)] were found more in the study in wet and dry seasons while cadmium was not detected in both seasons. Nickel showed high contamination factor of 48.24 – 42.40 in wet and dry season while cupper showed the least contamination factor of 0.012 – 0.008 in wet and dry season. The study has revealed that the surface water is not suitable for drinking purposes as seen by the high water quality index which the calculated value gave 1205.56-1236.26 for wet season and dry season which is > 300. The Hazard quotient via ingestion and Hazard quotient via dermal has a reduction in the order of lead > nickel > iron > manganese > copper > zinc and lead > zinc > nickel > copper > iron > manganese > cadmium, in cooperation in children and adults in wet season, correspondingly. The Hazard quotient via ingestion and Hazard quotient via dermal has a decrease in the following order of nickel > lead > manganese > copper > iron > zinc and lead >zinc > nickel > copper > manganese > iron > for both children and adults in dry season, respectively. Lead possess carcinogenic risk for the inhabitants of this area due to the value of the carcinogenic risk n wet season of 4.05E-4 in adult and 1.55E-3 in children, in dry season of 2.57E-4 in adult and 9.88E-4 in children, against the standard set by the USEPA of 10-6 – 10-4. The water pollution monitoring agency of this area should regularly check the water quality assessment of this river and should suggest treatment through filtration, boiling and the use of additives in order to reduce the risk of water related problems.