Spatiotemporal variability of drinking water quality and the associated health risks in southwestern towns of Ethiopia.

The failure to provide safe drinking water services to all people is the greatest development setback of the twenty-first century including Ethiopia. Potential pollutants from various sources are deteriorating drinking water quality in different seasons, and associated health risks were not clearly known. We determined seasonal and spatial variations of urban drinking water characteristics and associated health risks in Agaro, Jimma, and Metu towns, Southwest Ethiopia. Seventy-two samples were collected during dry and rainy seasons of 2014 and 2015. The majority (87.4%) of physicochemical parameters was found within the recommended limits. However, free residual chlorine in Jimma and Agaro town water sources was lower than the recommended limit and negatively correlated with total and fecal coliform counts (r = - 0.585 and - 0.638). Statistically significant differences were observed at pH, turbidity, and total coliform between dry and rainy seasons (p < 0.05). A Kruskal-Wallis H test revealed a statistically significant difference in electrical conductivity, total hardness, fluoride, iron, and fecal coliform across the study towns (p < 0.05). The Agaro town water source was the highest in fluoride concentration (3.15 mg/l). The daily exposure level for high fluoride concentration in Agaro town was estimated between 0.19 and 0.41 mg/kg day, and the average cumulative hazard index of fluoride was > 3.13 for all age groups. Water quality variations were observed in all conventional water treatment systems in the rainy season, and further research should focus on its optimization to safeguard the public.