(Bethesda, MD – Insurance News and Markets) – The National Cancer Institute, Geisel School of Medicine at Dartmouth, the U.S. Geological Survey, and departments of health in Maine, Vermont and New Hampshire collaborated on a study examining the potential that drinking water from wells dug in the first half of the 20th century could be a factor in the northern New England region’s elevated risk and incidence of bladder cancer.
The results of the study were published this month in the “Journal of the National Cancer Institute.”
Rates of bladder cancer in those three states are about 20 percent higher than in the entire United States overall, for both men and women. The region has a high percentage of the population that get their drinking water from private wells not maintained by cities and town services, and that are not subject to federal regulation. 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.
Arsenic can occur naturally, coming out of rock deep beneath the earth, but pesticides containing arsenic were also used extensively in the region on crops between the 1920s and the 1950s.
“Arsenic is an established cause of bladder cancer, largely based on observations from earlier studies in highly exposed populations,” said Debra Silverman, Sc.D., chief of the Occupational and Environmental Epidemiology Branch, NCI, and senior author on the study. “However, emerging evidence suggests that low to moderate levels of exposure may also increase risk.”
Researchers compared 1,213 people newly diagnosed with bladder cancer with 1,418 people without bladder cancer who lived in the same geographic areas as those who developed the disease.
“Although smoking and employment in high-risk occupations both showed their expected associations with bladder cancer risk in this population, they were similar to those found in other populations,” said Silverman. “This suggests that neither risk factor explains the excess occurrence of bladder cancer in northern New England.”
Researchers found that increasing exposure to drinking water containing arsenic was associated with an increased risk of bladder cancer. When investigators focused on participants who had used private wells, they saw that people who drank the most water had almost twice the risk of those who drank the least. This association was stronger if dug wells had been used. Dug wells are shallow, less than 50 feet deep, and potentially susceptible to contamination from manmade sources. Most of the dug well use occurred a long time ago, during an era when arsenic concentrations in private well water were largely unknown. However, the risk was substantially higher if the dug well use began before 1960 (when application of arsenic-based pesticides was commonplace in this region) than if dug well use started later.
Researchers were unable to precisely measure the arsenic exposure over participants’ entire lifetimes, which, they admit made it challenging to accurately quantify the contribution of arsenic exposure to the excess risk of bladder cancer.
“There are effective interventions to lower arsenic concentrations in water,” said 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. But we should emphasize that smoking remains the most common and strongest risk factor for bladder cancer, and therefore smoking cessation is the best method for reducing bladder cancer risk.”
Source: National Institutes of Health.