A new study has found that drinking water from private wells, particularly dug wells established during the first half of the 20th century, may have contributed to the elevated risk of bladder cancer that has been observed in Maine, New Hampshire, and Vermont for over 50 years. Other risk factors for bladder cancer, such as smoking and occupational exposures, did not explain the excess risk in this region. The study, by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, and colleagues at the Geisel School of Medicine at Dartmouth, Hanover, New Hampshire; the departments of health for Maine, New Hampshire, and Vermont; and the U.S. Geological Survey, appeared May 2, 2016, in the Journal of the National Cancer Institute.

Bladder cancer mortality rates have been elevated in northern New England for over half a century. The incidence of bladder cancer in Maine, New Hampshire, and Vermont has been about 20 percent higher than that in the United States overall. Rates are elevated among both men and women. A unique feature of this region is the high proportion of the population using private wells for their drinking water, which are not maintained by municipalities and are not subject to federal regulations. These wells may contain arsenic, generally at low to moderate levels. Previous studies have shown that consumption of water containing high concentrations of arsenic increases the risk of bladder cancer.