Municipal sewage sludge application on Ohio farms: estimation of cadmium intake

Abstract

This study was designed to estimate the contribution of municipal sewage sludge exposure and smoking to the daily Cd intake in Ohio farm residents, based on the Cd concentrations in 24-hr fecal samples. The fecal samples were analyzed for Cd and the daily Cd intakes were calculated by correcting for absorption (4.6%) in the gastrointestinal tract. Fecal samples from cattle grazing on sludge-treated pastures were also similarly treated except that published 24-hr fecal weights and a 2% absorption correction were used. Fecal weights and the daily Cd intakes, in humans, calculated from these data were significantly lower in females than in males with a female/male ratio of 0.77/1. Daily Cd intakes calculated from these data ranged from 5.37 to 13.31 micrograms/day for females and 8.87 to 18.52 micrograms/day for males. No significant increase in daily Cd intake resulted from exposure of humans to sludge on the farmlands. Although daily Cd intake for smokers was 1 microgram/day higher than for non-smokers, the difference was not statistically significant. Cattle grazing on sludge-treated pastures consumed significantly more (up to 3 times) Cd than cattle on control pastures. It was concluded that application of sewage sludge on farmlands at rates of 2-10 dry metric tons/ha did not significantly contribute to the daily Cd intake in humans; cattle on such farms, however, significantly increased their Cd consumption.