Drinking Water Quality and its Relationship with the Mortality Rate in Okinawa Prefecture

Abstract

The objectives of this study were to analyze the correlations between mortality rates and drinking water quality in Okinawa prefecture, where the environmental conditions such as the weather, dietary habits and way of living, etc. exist within the same aspect. The qualities of 75 stream waters and 20 municipal drinking waters, the relationships between 15 component concentrations in drinking waters and 14 mortalites in female, 12 ones in male and 12 ones in both sexes were investigated for Okinawa prefecture. The main findings were as follows: 1. Comparing the average concentrations of the stream waters in various areas, the concentration of dissolved solids was found to be higher for Okinawa prefecture than these for other prefectures of Japan and the world, and in Okinawa prefecture that of dissolved solids was found to be much higher for its calcareous area than for its non-calcareous area. The same trends in drinking waters as the stream waters were shown, because the concentrations of drinking waters depended principally on the features of their sources. 2. Positive correlations were found between death rate from ischemic heart disease in female and concentrations of ABS, PO₄ and SO₄ with respective correlation coefficient r=0.706 (p<0.001), 0.590 (p<0.01) and 0.549 (p<0.05). 3. Plotting the scores obtained by principal component analysis in which four variables were the mortality from ischemic heart disease in female and the concentrations of ABS, P0₄ and SO₄, the lowest mortalities clustered on the 3rd quadrant and the highest ones on the 1st quadrant. All of 4 drinking water sources of municipalities which had worst 4 mortalities were located in the calcareous area of the central part of Okinawa mainland. 4. A multiple regression analysis, where the mortality (Y) from ischemic heart disease was employed as criterion variable and the concentrations (X₁, X₂ and X₃) of ABS, P0₄ and S0₄ as explanatory variables, was conducted to estimate the mortality from the concentration variable of drinking water . As a result of the multiple regression analysis, the following equation was introduced. Y=17.9 + 45.3X₁-14.3X₂-0.04X₃ By F-test, high statistical signif icances were shown for the equation and the regression coefficient of ABS concentration at critical rates of respective 1% and 5%. 5. Uterine cancer mortality correlated positively with F concentration in drinking water (r=0.633, p<0.001) 6. Mortality from liver cancer in both sexes related positively to N0₃-N + NO₂-N concentration (r = 0.601, p <0 .01) and negatively to SiO₂ and K concentrations (r=-0.520, p<0.05 and r=-0.516, p<0.05) in drinking water.