Drinking Water Quality and Public Health in the Kathmandu Valley, Nepal: Coliform Bacteria, Chemical Contaminants, and Health Status of Consumers

Abstract

Residents of Nepal's Kathmandu Valley draw drinking water from tube wells, dug wells, and stone spouts, all of which have been reported to have serious water quality issues. In this study, we analyzed drinking water samples from 35 tube wells, dug wells, stone spouts, and municipal tap water for bacterial and chemical contaminants, including total and fecal coliform, aluminum, arsenic, barium, beryllium, boron, cadmium, cobalt, chromium, copper, fluoride, iron, mercury, manganese, molybdenum, nickel, lead, antimony, selenium, thallium, uranium, vanadium, and zinc. We also asked a sampling of households who used these specific water sources to rate the taste of their water, list any waterborne diseases they were aware of, and share basic health information about household members. This survey provided us with information from 146 households and 603 individuals. We found widespread bacterial contamination of water sources, with 94% of sources having detectable total or fecal coliform. Nepal Drinking Water Quality Standards and World Health Organization (WHO) Drinking-Water Guidelines or health-based values were exceeded for aluminum (max = 0.53 mg/L), arsenic (max = 0.071 mg/L), iron (max = 7.22 mg/L), and manganese (max = 3.229 mg/L). The distribution of water sources with high arsenic, iron, and manganese appeared to be associated with floodplain deposits. Mixed effects logistic regression models were used to examine the interactions between social factors and water contaminants and their effects on household members' health. Consumers of water sources with both high and low concentrations of manganese were less likely to have a positive attitude towards school than those whose water sources had moderate concentrations of manganese. Social factors, especially education, played a large role in predicting individual health outcomes. Household taste ratings of drinking water were not correlated with iron or manganese concentrations, suggesting that WHO's reliance on aesthetic criteria for these contaminants instead of formal drinking-water guidelines may not be sufficient to protect public health.

Figure 1

(a) Location and elevation map of Nepal and Kathmandu. (b) Location map of Asia and Nepal. Elevation data is from the SRTM 90 m digital elevation database [53].

Figure 2

Location map of sample sites, major rivers, and geologic formations underlying the Kathmandu Valley. The mapping of geologic formations was based on the engineering and environmental geologic map by Shrestha et al. [61].

Figure 3

Concentration maps of total and fecal coliform for each sample site. Map symbols indicate the type of water source as well as concentration value. The geologic contact and extent of floodplain sediments are from Shrestha et al. [61].

Figure 4

Concentration maps of iron, arsenic, and manganese for each sample site. Map symbols indicate the type of water source as well as concentration value. Green symbols indicate values that fall below WHO health-based values (HBVs); red symbols indicate sites that are above WHO HBVs. The geologic contact and extent of floodplain sediments is from Shrestha et al. [61]. (a) Iron. (b) Arsenic. (c) Manganese.