'Safe' levels of arsenic in drinking water could harm pregnant mothers and offspring

By Chelsea Whyte on June 1, 2012 2:37 PM EDT

water faucet
Is your drinking water safe? The U.S. Environmental Protection Agency says low doses of arsenic are okay, but a new study finds otherwise. (Photo: Pemanducomm)

The checklist of things to avoid when you're pregnant seems to be getting longer. Tuna fish, alcohol and caffeine are well-known no-nos for expectant mothers, but now they may have to add tap water to the list.

Low levels of arsenic in drinking water (10 parts per billion), which are currently considered safe for human consumption by the U.S. Environmental Protection Agency (EPA), have been found to have adverse affects on pregnant and lactating mothers, as well as their offspring.

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In a study of pregnant and lactating mice, researchers Joshua Hamilton of the Marine Biological Laboratory (MBL) and Courtney Kozul-Horvath at Geisel School of Medicine at Dartmouth found that even at 'safe' doses, drinking arsenic-laden water led to lower nutrients in the blood and breast milk. Though the mother mice carried their offspring to term and had litters of usual size, their pups grew more slowly than the control group that drank arsenic-free water.

"The pups were essentially malnourished; they were small and underdeveloped," said Hamilton. When pups were switched to uncontaminated milk from mothers who hadn't consumed arsenic, their developmental deficiencies were reversed, though only the males fully caught up with the growth of pups that had no arsenic exposure.

"In the mom's blood and breast milk, there were significant decreases in triglycerides - an important nutrient for mom and baby," Hamilton told Fox News. "It was the principal reason the babies were under-developed. When we took new born pups with arsenic moms and switched them over to feed from non-arsenic moms, they started to recover. So it suggested it was a nutrient problem, not a direct effect of the arsenic on them but on the mother."

Arsenic in drinking water disrupted the mother mouse's ability to store fats that nourish a baby. "Normally, the body is very good at storing fat and glucose for later use," said Hamilton. "Up to a certain point, if a mother is malnourished during and after pregnancy, the offspring will not be compromised, because her body uses nutrients it has stored to nourish the baby."

But in this case, that protective mechanism is compromised, which leaves fewer nutrients for nursing pups. The mothers exposed to arsenic also had abnormal accumulations of fat in their livers.

"We have to think again about whether 10 ppb arsenic as a U.S. drinking water standard is safe and protective of human health," said Hamilton.

David Polya of the University of Manchester, UK, who was not involved in the work, told New Scientist that humans and mice show significantly different responses to arsenic, but the results are still important. 

Researchers have linked arsenic with negative health effects in people, such as increased risks of respiratory infections and cancer, reports My Health News Daily. However, most work has been done in countries with markedly high arsenic levels, in the range of several hundred ppb, according to the study.

The U.S. EPA recently lowered the Maximum Contaminant Level for arsenic to 10 ppb in public water supplies, which is considered "safe" for a lifetime of exposure. But, according to the study, concentrations of 100 ppb and higher are commonly found in private, unregulated well water in regions where arsenic is geologically abundant, including upper New England (Massachusetts, New Hampshire, Maine), Florida, and large parts of the Upper Midwest, the Southwest, and the Rocky Mountains.

Aaron Barchowsky of the University of Pittsburgh said the EPA is convening an advisory panel to evaluate the human and animal data on arsenic risk for non-cancer diseases to determine whether the 10 ppb limit is adequate to protect human health, reports New Scientist.

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