HEALTH RISK ASSESSMENT OF SURFACE WATER FROM ORHIONMWON RIVER, SOUTHERN NIGERIA
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Abstract
This study assessed the health risk assessment of surface water from Orhionmwon River, Southern Nigeria. A total of 18 water samples were collected at each location from May 2025 to July 2025. From upstream to downstream, water samples were taken from three locations in accordance with normal guidelines. While certain heavy metals were identified using the method of the association of analytical chemistry, the physicochemical properties of surface water were analysed using normal laboratory procedures. The average mean concentration of physicochemical and heavy metal properties in surface water were 30.12±0.20 (temperature), 6.97±0.13 (pH), 20.00±1.20 (EC), 9.89±0.51 (TDS), 4.50±0.17 (TSS), 14.39±0.48 (TS), 6.38±0.27 (turbidity), 5.76±0.59 (alkalinity), 4.84±0.32 (DO), 3.71±0.08 (BOD), 33.78±11.04 (COD), 6.61±0.78 (chloride), 7.61±2.34 (NO3), 0.47±0.25 (PO4), 1.84±0.19
(SO4), 6.92±0.31 (hardness), 1.80±0.16 (Ca), 0.63±0.10 (Mg), 0.87±0.06 (Na), 1.50±0.08 (K), 1.24±0.08 (Fe), 0.11±0.01 (Cu), 0.61±0.08 (Zn), 0.06±0.01 (Pb), 0.28±0.08 (Mn), 0.05±0.01
(Cr) and 3.96±0.15 (THC) respectively. Cadmium was not detected in the surface water from Orhionmwon River. The summative water quality index (WQI) for the three sampled stations were classified Grade E indicating that the water from Orhionmwon River is unsuitable for drinking (>100). The comprehensive pollution index across the sampled stations were classified as slightly polluted. Non-carcinogenic target hazard quotients (THQs) for oral exposure for the heavy metals were < 1.0 except for THC across the sampled stations, which suggests that consumers of water from these locations may be at high risk of non- carcinogenic illnesses associated with THC contaminants. The hazard index (HI) values for oral exposure shows that (HI > 1) which indicates that the consumption of the water predisposes them to potential health risk. The result for the integrated carcinogenic risk (ICR) values classified the surface water from Orhionmwon River as Grade VI (high risk – 10 -3) which calls for immediate attention and adequate action and should be further investigated for heavy metals such as lead and chromium
(SO4), 6.92±0.31 (hardness), 1.80±0.16 (Ca), 0.63±0.10 (Mg), 0.87±0.06 (Na), 1.50±0.08 (K), 1.24±0.08 (Fe), 0.11±0.01 (Cu), 0.61±0.08 (Zn), 0.06±0.01 (Pb), 0.28±0.08 (Mn), 0.05±0.01
(Cr) and 3.96±0.15 (THC) respectively. Cadmium was not detected in the surface water from Orhionmwon River. The summative water quality index (WQI) for the three sampled stations were classified Grade E indicating that the water from Orhionmwon River is unsuitable for drinking (>100). The comprehensive pollution index across the sampled stations were classified as slightly polluted. Non-carcinogenic target hazard quotients (THQs) for oral exposure for the heavy metals were < 1.0 except for THC across the sampled stations, which suggests that consumers of water from these locations may be at high risk of non- carcinogenic illnesses associated with THC contaminants. The hazard index (HI) values for oral exposure shows that (HI > 1) which indicates that the consumption of the water predisposes them to potential health risk. The result for the integrated carcinogenic risk (ICR) values classified the surface water from Orhionmwon River as Grade VI (high risk – 10 -3) which calls for immediate attention and adequate action and should be further investigated for heavy metals such as lead and chromium
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