"This work supports the idea that arsenic in drinking water can promote the carcinogenic effects of other chemicals," says Angeline Andrew, the lead author and a research assistant professor of community and family medicine at Dartmouth Medical School. "This is evidence that it's more important than ever to keep arsenic out of drinking water."
The study, which was published online on May 10, 2006, in the journal Environmental Health Perspectives, examined the drinking water and measured the arsenic levels in samples of urine and toenails of people who were enrolled in epidemiologic studies in New Hampshire, and in Sonora, Mexico.
Andrew and her colleagues examined the data in conjunction with tissue samples from the study participants to determine the effect of arsenic on DNA repair. To further corroborate their findings, the researchers conducted laboratory studies to examine the effects of arsenic on DNA repair in cultured human cell models.
"The DNA repair machinery normally protects us from DNA-damaging agents, such as those found in cigarette smoke," says Andrew. "The concern is that exposure to drinking water arsenic may exacerbate the harmful effects of smoking or other exposures."
Andrew explains that in regions of the United States where the rock contains higher levels of arsenic, the greater the likelihood that drinking water sources contain some potential adverse levels of the toxin. While the levels of arsenic in municipal water systems are regularly monitored, there is no mandated testing of arsenic levels in private wells. This is of particular concern since the regions where arsenic levels are high are in rural regions, such as New Hampshire, Maine, Michigan and some regions of the Southwest and Rockies. Private wells are common in these areas as primary sources of drinking water.