Heavy metal by Margot Higgins
Of the Environmental Protection Agency’s hit list of the nation’s most toxic chemicals, arsenic ranks first. Since ancient times, the chemical has been regarded as a poison of choice.
Scientists recently discovered that low-dose exposure to arsenic may increase the risk of certain types of cancer, diabetes and vascular disease. A 1999 report by the National Academy of Sciences confirmed that arsenic in drinking water causes bladder, lung and skin cancer, and might cause kidney and liver cancer.
Now a team of researchers at the Dartmouth Medical School has discovered that arsenic may play a role in endocrine disruption.
The findings, published in the journal Environmental Health Perspectives, may offer important information on how arsenic causes a variety of the diseases to which it has been linked.
“This is unlikely to be the only mechanism underlying diseases associated with low-level arsenic exposure, but we expect it will be an important contributor,” said Joshua Hamilton, lead author of the study.
Endocrine disrupters confuse the normal activity of hormones, which are critical to the proper growth, development and function of various tissues in wildlife and humans.
Most work on endocrine disrupters has focused on chemicals that block or mimic the estrogen hormone.
According to the Dartmouth study, arsenic disrupts a different hormone — the glucocorticoid receptor — which regulates a wide range of biological processes.
Instead of mimicking or binding to the hormone’s receptor as organic endocrine disrupters such as pesticides do, arsenic disrupts the hormone in a way that was not previously understood by scientists.
In an upcoming study, Hamilton’s research team will examine whether the effects they have observed in cultured cells also occur in animals and humans that are exposed to arsenic.
While arsenic is the first metal to be linked with endocrine disruption, a number of other metals could have the same impact, Hamilton notes. There are eight metals of concern on the EPA’s toxic chemicals list.
Arsenic is found at many toxic waste sites through the disposal of compounds from industrial and mining practices. Significant levels of the chemical have been detected at 70 percent of the Superfund sites inspected for the chemical.
Arsenic can also accumulate in groundwater and well water from natural sources. Arsenic levels have been a major problem in areas of Taiwan, South America, India and Pakistan.
Certain regions in the United States also contain arsenic in their drinking water supply, especially in private wells that are not routinely tested by the EPA.
In New Hampshire, for example, 40 percent of the population consumes water from private wells, and 25 percent of those wells have high arsenic levels.
“A lot of us are exposed unknowingly because arsenic has no taste, smell or odor,” Hamilton said. “The only way to detect it is to test it. Here in New Hampshire we are trying to get all private well owners to test for arsenic.”