Exposure to arsenic through drinking water can have deleterious effects on reproductive and developmental processes in humans and animals. As a result, the US Environmental Protection Agency (EPA) has established a maximum acceptable concentration for arsenic in drinking water. This limit was 50 ppb until 2001, when it was reduced to 10 ppb because of concerns that higher levels were associated with increased cancer risks. Since then, researchers, including Joshua W. Hamilton (Marine Biological Laboratory, Woods Hole, MA), have continued to investigate the effects of lower concentrations of arsenic on development and disease.

Hamilton and colleagues provided pregnant and lactating C57B6/J mice with drinking water containing 10 ppb arsenic, the maximum level allowed by the EPA. They observed problems with lipid metabolism in the mice, which led to lower levels of triglycerides in their blood and breast milk. These deficiencies stunted the growth of the exposed mice's offspring (PLoS One 7, e38249; 2012). When these offspring were fostered by a different dam that had not been exposed to arsenic, the pups grew more normally.

The study results show that exposure to arsenic at the maximum concentration allowed by the EPA during pregnancy and lactation has adverse effects on the health of adult female mice and their offspring. Hamilton's team hopes to carry out more experiments to elucidate the physiological mechanisms underlying the effects of arsenic exposure. They also plan to examine the potential effects of in utero and post-natal exposure to arsenic on pups as they grow to adults and on the next generation of pups.

Hamilton's results contribute to growing concern that the limit of 10 ppb arsenic in drinking water is not sufficient to protect human health. “I think as a community in toxicology, we're seeing more and more studies that are suggesting that 10 ppb may not be protective enough for humans,” Hamilton told FoxNews.com.

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The EPA is reportedly considering whether the limit should be reduced. Factors such as the availability and cost of technology that can effectively reduce arsenic concentrations in water and of tools that can reliably measure these low concentrations, as well as the high costs associated with enforcing a reduced limit, must be considered. New Scientist reported that Aaron Barchowsky (University of Pittsburgh, PA), a toxicologist who researches health effects of arsenic in drinking water but who did not participate in Hamilton's study, estimated that enforcing a reduced limit of 2 ppb arsenic in drinking water in the US could cost trillions of dollars.