Nitrates also are a by-product of municipal waste treatment.
And while some have found an association with such diseases as non-Hodgkin's lymphoma, there has only been one study done in Spain, published in 1993, that showed an association between nitrate, a municipal water supply and an increased risk for bladder cancer. Bladder cancer is the sixth most common cancer in the United States. The American Cancer Society predicts about 53,200 new cases of bladder cancer in 2001 in this country. About 12,200 Americans will die of the disease, which is more common among men than women, although no one knows why. Weyer and his colleagues used data from more than 41,000 women, aged 55 or older, in the Iowa Women's Health Study.