Public health risks associated with drinking water consumption in the upper Awash River sub-basin, Ethiopia, sub-Saharan Africa

The Upper Awash sub-basin characterized by urban, industrial, agricultural and population growth, has impacted the quality of its water sources. This study focuses on the assessment of public health risks associated with drinking water sources in the sub-basin. In accordance with WHO guidelines, 120 water samples were collected from 60 water supply schemes in dry and wet seasons located in areas with low and high water pollution risk (WPR). Multi-meter, Photometer, Digital Arsenator, and Microbiological test kit measured the concentration of parameters. The assessment uses methods of hazard identification, exposure and dose-response analysis, and risk characterization, including Hazard Quotient (HQ), Cancer Risk (CR), Hazard Index (HI), and probability of infection. Monte Carlo simulation analyzes non-cancer risks from Nitrite, Nitrate, Chromium, Iron, Fluoride, and Arsenic, and CRs from Chromium and Arsenic, and infection risks from Escherichia coli (E.coli). As a result, the Hazard Quotient (HQ) of Nitrate was beyond unity (HQ > 1) in the dry season for all groups. HQ of Chromium was HQ > 1 for Women (1.1E+00) and Children (1.4E+00) in the wet season in the high WPR area. Chromium HQ > 1 for children (1.4E+00) in the wet season and Fluoride (HQ > 1) for Children (3.2E+00) in the dry season in the low WPR area. Arsenic CR was above 1 in 10,000 persons for children in the dry season, for all groups, and for women and children in the wet season in the high WPR areas. The CR of chromium ranged from 1 in 1000 persons, which is beyond the limit. Moreover, the Hazard Index (HI) was higher than the unity (HI > 1) for most cases. All E coli infection risks daily and annually exceeded the acceptable risks. Therefore, Public health concerns in the Sub-basin were quantified, and evidences were generated for risk management to undertake source protection through integrated watershed management and appropriate water treatment technologies.