Is Your Drinking Water Giving You Diabetes?

Arsenic, a common trace contaminant in well water, has been linked to type 2 diabetes.

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The heavy metal arsenic, which occurs naturally as an element of the Earth's crust, has a long history as an instrument of murder. The notorious Borgia family of Italy, including Pope Alexander VI, is said to have used the tasteless, colorless, and odorless substance to regularly dispatch enemies, and even a despot of Napoleon Bonaparte's stature may have fallen victim to an orchestrated overdose. More recently, scientists have proved that chronic exposure to drinking water contaminated with arsenic can cause cancers of the bladder, lung, kidney, and skin, as well as a collection of other diseases. Now there's a new twist. Research published today in the Journal of the American Medical Association has linked the ancient poison to type 2 diabetes, a disease that has reached pandemic proportions and now accounts for 1 in every 10 American dollars spent on healthcare. And trace amounts of naturally occurring arsenic seem to be contributing to the problem—and endangering some Americans without their knowledge, experts say.

Johns Hopkins researchers found that the risk of diabetes for Americans with the highest inorganic arsenic loads in their urine is more than three times the risk for those with the lowest arsenic loads. The new finding buttresses previous research in animals that shows exposure to arsenic increases blood glucose and insulin levels. It's also consistent with studies from Taiwan, Bangladesh, and Mexico that link high levels of arsenic to diabetes. The new study examined inorganic arsenic exposure in a representative sample of Americans nationwide. (Organic arsenic, which is found in seafood, is not thought to pose a health risk.)

There's a take-home message for many Americans. While utility companies are required by law to keep arsenic levels in drinking water below 10 parts per billion, fewer safeguards exist for the approximately 15 percent of Americans who quench their thirst with water from private wells. So, many people may have high levels of arsenic in their water and not realize it, says Ana Navas-Acien, a physician and epidemiologist at Johns Hopkins University who is the study's lead author.

"People who get their drinking water from private wells and live in areas where groundwater is naturally contaminated with arsenic are at an especially high risk of being exposed to water with levels above the 10 parts per billion acceptable limit set by the Environmental Protection Agency," Navas-Acien says.

The good news: A cheap lab test—typically only $20 to $35—can determine whether a household's well is contaminated. If it is, water filters or other water quality improvement strategies can remedy the problem.

Arid states in the West have some of the most arsenic-contaminated groundwater in the country, but midwestern and eastern states are also known to have certain areas with heavily arsenic-laced water. The United States Geological Survey maintains nationwide maps of arsenic levels that are a helpful resource for people wondering about their local area. Typically, arsenic is a problem in deep wells, not surface waters. According to the Department of Health and Human Services, filtering done by reverse osmosis, distillation, or special iron and aluminum units can remove arsenic; water softeners and pitcher filters cannot. NSF International maintains a useful database of filters.

For households with arsenic-contaminated wells, bottled water can be a good short-term solution (though it is important to ensure that the bottled water is actually clear of the metal—something that's not necessarily a guarantee, as this report from an environmentalist group and a 2007 recall of Jermuk mineral water suggest). Longer-term remedies involve putting in a new well using appropriate precautions or connecting to a public water supply. Sites from the Environmental Protection Agency, the Centers for Disease Control and Prevention, and the Department of Health and Human Services offer more advice for consumers confronting high arsenic levels in their wells.