Study Correlates NH Private Well Water and Bladder Cancer

A study published by the National Cancer Institute (NCI) found that drinking water from private wells, particularly dug wells established during the first half of the 20th century, may have contributed to the 50 year rise in bladder cancer risk for Maine, NH and Vermont residents. 

The study was conducted through a partnership of researchers at NCI and the Geisel School of Medicine at Dartmouth College in Hanover, the latter of which published a similar study in 2014. The researchers worked with the departments of health for Maine, NH and Vermont; and the U.S. Geological Survey.

Bladder cancer mortality rates in northern New England have risen for both men and women, with incidence of bladder cancer in the region being about 20 percent higher than in the U.S. overall. Other risk factors for bladder cancer, such as smoking and occupational exposures, did not explain the excess risk in this region.

However, a unique feature of the region is the elevated use of drinking water from private wells, which aren’t maintained by municipalities or subject to federal regulations and may contain low to moderate levels of arsenic.

Arsenic in the region’s well water has two possible sources:

• Naturally-occurring arsenic released from rock deep in the earth.
• Arsenic-based pesticides used extensively on crops from the 1920s through the 1950s.

"Arsenic is an established cause of bladder cancer, largely based on observations from earlier studies in highly exposed populations," says Debra Silverman, chief of the occupational and environmental epidemiology branch at NCI. "However, emerging evidence suggests that low to moderate levels of exposure may also increase risk."

The researchers conducted a large study of residents of the region, comparing risk factors and estimated exposure to arsenic from well water among 1,213 people newly diagnosed with bladder cancer and 1,418 people without bladder cancer.

The study found an association between increases in cumulative exposure and risk of bladder cancer, with that risk doubling for people who drank the most water from private wells. This association was stronger with the use of dug wells, which are shallow and potentially susceptible to contamination from manmade sources. 

The likelihood of exposure to arsenic from dug wells has diminished since arsenic-based pesticides are no longer used. However, possible current exposure to arsenic in drinking water, through use of private wells drilled deeply into fractured bedrock, is a potential public health concern.

"There are effective interventions to lower arsenic concentrations in water," says Silverman. “New England has active public health education campaigns instructing residents to test their water supply and to install and maintain filters if levels are above the EPA threshold.”