Chlorination, water hardness and serum cholesterol in forty-six Wisconsin communities.

The Wisconsin Heart Health Research Program measured serum lipids and other clinical parameters among residents of 46 neighbouring small communities in central Wisconsin. The purpose of the study was to determine whether distribution of serum lipids, blood pressure or thyroid hormones differed according to the chlorination of water supply, or to its calcium and magnesium content (hardness). This report examines serum lipid levels in relation to the drinking water characteristics chlorination and hardness. Variables measured on individuals included age, education level, alcohol intake, cigarette smoking, dietary fat and dietary calcium. An analysis of covariance was used to estimate effects of chlorination and hardness on each of the serum lipids, with individual variables included as covariates. Among females, serum cholesterol (SC) levels are significantly higher in chlorinated communities than in non-chlorinated communities. Community SC levels are also higher for males in chlorinated communities, on the average, but differences are smaller and not statistically significant. Low density lipoprotein (LDL) cholesterol levels follow a similar pattern to that for total SC levels, higher in chlorinated communities for females, but not different for males. On the other hand, high density lipoprotein (HDL) cholesterol community means are nearly identical in the chlorinated and non-chlorinated communities for each sex.