Jeff Nichols, a technician with the Agricultural Research Service, collects a water sample from the Walnut Creek watershed in Ames, Iowa. Samples are collected weekly from Walnut Creek and surrounding watersheds to study the effects of farming on water quality. Nitrate is one of the most common groundwater contaminants in rural areas. A new study of 22,000 Iowa women has found that nitrate in drinking water is associated with an increased risk for bladder cancer. While nitrate is produced naturally within the body and within certain foods, environmental sources include contaminated drinking water, cigarette smoking and some medications.
Drinking water can account for a substantial proportion of a person's total nitrate intake.
The University of Iowa researchers found that up to 20 percent of ingested nitrate is transformed in the body to nitrite, which can then undergo transformation in the stomach, colon and bladder to form N-nitroso compounds. These compounds are known to cause cancer in a variety of organs in more than 40 animal species, including higher primates. The U.S. Environmental Protection Agency drinking water standard is 10 mg per liter nitrate-nitrogen. The presence of nitrites in infants under 6 months old is a known problem. Babies of mothers who prepare formula using tap water are particularly at risk.