Ding dong dell, arsenic in the well
By Roger P. Smith, Ph.D.
New Hampshire's municipal water supplies are carefully monitored for arsenic and other toxins. But Granite Staters who get their drinking water from a private well—as do 40% of residents—might be less safe. A recent analysis of several thousand private wells in the state found that one in four have naturally occurring arsenic at levels that Joshua Hamilton, Ph.D., director of DMS's Center for Environmental Health Sciences, considers potentially dangerous. The highest levels found in the study were 100 parts per billion (ppb). That's not much—the equivalent of just one large mouthful of food out of all the food 10 people would eat in their lifetimes. Even those who drink water from a 100 ppb well their whole lives wouldn't consume enough to cause clinical signs of poisoning like those in the murder mystery Arsenic and Old Lace. But, says Dartmouth epidemiologist Margaret Karagas, Ph.D., 100 ppb is enough to put people at greater risk of developing skin or bladder cancer.
Scientists have been divided for many years on the question of whether or not arsenic causes cancer. Cancers are now believed to pass through a number of obligatory precancerous stages before they become malignant tumors, and there are opportunities at each stage to reverse or prevent the tumor's progression. DMS toxicologist Angeline Andrew, Ph.D., was the lead author of a recent paper in Environmental Health Perspectives examining arsenic's role in this process.
Repair: Tumor progression begins with the initiation phase, when a carcinogen—such as a highly reactive chemical or radiation—damages DNA. Then comes the promotion phase, when exposure to other chemicals facilitates progression of the lesion toward cancer. In most people, enzymes can repair damaged DNA and reverse the cancer progression. But when Andrew looked at DNA repair enzymes in the lymphocytes of New Hampshire residents, she found a strong correlation between arsenic levels in their urine and toenails—which correlated closely with levels in their well water—and levels of a key enzyme, ERCC1. In those exposed to the most arsenic, ERCC1 was almost totally suppressed.
The researchers hypothesize that arsenic is not a true carcinogen, or initiator, but a promoter. So in people exposed to a carcinogen that can damage DNA, such as cigarette smoke or the sun's ultraviolet radiation, arsenic promotes the damaged cells' progression to cancer by suppressing their DNA-repair mechanism.
DMS's Center for Environmental Health Sciences is doing more than studying the science behind such processes. Dartmouth officials are also working with state agencies to make sure that Granite Staters are informed on the subject of arsenic in well water. Information about testing private wells is available from the Department of Environmental Services' Water Supply Engineering Bureau at 603-271-3445. Information about remediation options and prices is available at the New Hampshire Department of Environmental Services site..
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