Appraising the water quality of Eto-anen stream in Ibotio, Mkpat Enin Local Government Area, Akwa Ibom State, Nigeria, using pollution, ecological and human health risk approach

Water, as an essential component of the ecosystem, is required in good condition for proper ecological and economic processes. Surface water samples were collected and analyzed in accordance with recommended standards. Metal concentrations were determined using an atomic absorption spectrophotometer. The physicochemical parameters, temperature, pH, turbidity, electrical conductivity, dissolved oxygen, total dissolved solids, total suspended solids, salinity as Clˉ, total hardness, total alkalinity, and bicarbonate, were 29°C, 5.86, 4.06NTU, 41.1µS/cm, 3.65mg/L, 20.4mg/L, 0.064mg/L, 24.82mg/L, 90mg/L, 65mg/L, and 79.3mg/L accordingly. The water quality index (WQI) of 21.153, evaluated using physicochemical parameters, indicates excellent water quality. Values for heavy metals obtained in surface water were in the order Hg<Co<As<Mn<Ni<Cr<Pb<Cd<Cu<Zn<Fe. The results indicate that the concentrations of metals exceeded the recommended limits set by WHO and NSDWQ, except for Hg, Co, As, and Mn. Contamination index ranged from 0.167 to 701.66. The Nemerow integrated pollution index was 499.049. Pollution load index was 3.895, and the geoaccumulation index ranged from -3.170 to 8.870. The indices indicate that the metals had a moderate to very high degree of contamination, except for Mn, As, Co, and Hg. The average daily intake of the metals via ingestion, dermal contact, and inhalation ranged between 4.92E-13 to 6.56E-05 and 2.11E-13 to 7.02E-06 for children and adults, respectively. These values were lower than their corresponding estimated daily intake rates from the USEPA. Target hazard quotient for children (3.94E-06 to 2.69E-02) and adults (4.22E-07 to 2.88E-03), and the hazard index for children (3.14E-02) and adults (3.37E-03) were <1, depicting no health risk. Incremental lifetime cancer risk for children (2.89E-08 to 3.45E-05) and adults (3.42E-09 to 5.80E-06), and the total cancer risk for children (6.35E-05) and adults (1.06E-05) were within the probable negligible risk of 10⁻⁶ - 10⁻⁴. By implication, surface water poses no cancer risk to potential consumers.