Concentration and Health Implication of Heavy Metals in Drinking Water from Urban Areas of Tigray Region, Northern Ethiopia

The study was undertaken to assess the status of drinking water quality in the urban areas of the Tigray region, northern Ethiopia. A total of 106 drinking water samples were collected from 16 densely populated urban areas of the region, viz.: Alamata, Korem, Maichew, Adigudom, Abyi-Adi, Hagereselam, Zalambessa, Adigrat, Edagahamus, Firewoini, Wukro, Mekelle, Indaselassie, Axum, Adwa, and Enticho. All the samples were analyzed for six physicochemical parameters such as temperature, conductivity, total dissolved solids (TDS), salinity, pH, and turbidity and ten heavy metals,viz., As, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, and Zn using standard procedures. The results were compared with other national and international standards. Among the analyzed samples, regarding physicochemical parameters, 84.01 % for electrical conductivity, 47.17 % for TDS and 31.13% for turbidity show concentrations higher than the WHO (2008) recommended values. More than 93.4% of the samples were within the United States Environmental Protection Agency (US EPA) admissible pH limit (6.5-8.5) and all the samples analyzed were within the EU (1998) admissible pH limit (6.5-9.5). All samples contain manganese and copper within the WHO (2008) maximum admissible limit, but arsenic (40.3 %), cadmium (7.46 %), chromium (64.18 %), iron (37.31 %), nickel (7 %), and lead (29.85 %) crossed the maximum admissible and desirable limits recommended by WHO (2008). The maximum admissible limit of cobalt in drinking water is not mentioned by WHO, but all the samples analyzed were found to comply the New Zealand (1000 μg/L) and US EPA (100 μg/L) maximum admissible limits. Although no guideline is set by WHO (2008) for Zinc level in drinking water, of the samples analyzed, 94.02% comply the New Zealand standard and 97.01% comply all the maximum admissible limits referred in the present study. In general, the results of the present study have shown that some of the physico-chemical parameters have shown values higher than the WHO (2008) recommended maximum admissible limits. This is an indication of pollution hazards and weak drinking water treatment practices in the areas, which in turn have important human health implications. This study, therefore, recommends the government and other responsible authorities to take appropriate corrective measures.