Leukemia incidence and radioactivity in drinking water in 59 Iowa towns.

Fifty-nine towns in Iowa with single source drinking water supplies were stratified on the basis of radium content in finished non-softened water to test the hypothesis of an association with total or acute myeloid leukemia. Fourteen towns had radium concentrations in drinking water exceeding the EPA safety limit of 5 picocuries per liter (pCi/L). A small increasing trend existed for total leukemia with increased radium content in drinking water that is in accordance with either the hypothesis of no effect or of a small effect.