Development of impact factors on damage to health by infectious diseases caused by domestic water scarcity

Background, aim, and scope Water scarcity is a critical environmental issue. In particular, domestic water is a necessary resource for our fundamental activities, and poor water quality may lead to damage to health caused by infectious diseases. However, there is no methodology to assess the damage of domestic water scarcity (low accessibility to safe water) caused by water consumption. The main objectives of this study are to model the health damage assessment of infectious diseases (ascariasis, trichuriasis, hookworm disease, and diarrhea) caused by domestic water scarcity and calculate damage factors on a country scale. Materials and methods The damage to health caused by infectious diseases was assumed to have resulted from domestic water scarcity due to loss of accessibility to safe water. Damage function of domestic water scarcity was composed of two steps, including assessments of water accessibility and health damage. This was modeled by applying regression analyses based on statistical data on a country scale. For more precise and realistic modeling, three explanatory variables (domestic use of fresh water, gross domestic product per capita and gross capital formation expenditure per capita) for water accessibility assessment and seven explanatory variables (the annual average temperature, the house connection to water supply, the house connection to sanitation, average dietary energy consumption, undernourished population rate, Gini coefficient of dietary energy consumption, and health expenditure per capita) for the health damage ssessment were chosen and non-linear multiple regression analyses were conducted. Results Water accessibility could be modeled by all three explanatory variables with sufficient explanatory power ( R 2 = 0.68). For the health damage assessment, significant explanatory variables were different from those for diseases, but the R 2 values of the regression models for each infectious disease were calculated as more than 0.4. Furthermore, the house connection to water supply rate showed a high correlation with every infectious disease. This showed that domestic water scarcity is strongly linked to health damage caused by infectious diseases. Based on the results of the regression analyses, the calculated damage factors of domestic water scarcity ranged from 1.29E-11 to 1.81E-03 [Disability Adjusted Life Years (DALYs)/m 3 ], and the average value (weighted mean value by domestic use of fresh water for each country) was 3.89E