When researchers from the Marine Biological Laboratory (MBL) and at Geisel School of Medicine at Dartmouth began feeding mice low levels of arsenic considered safe for human consumption in drinking water by the Environmental Protection Agency, they intended to study the heavy metal‘s affect on the immune system and susceptibility to the flu, but they didn’t get that far. The team instead concluded that legal levels of arsenic in drinking water might be harmful to women and children.
Pregnant and/or breastfeeding mothers who consumed low levels (10 ppb) of arsenic in their drinking water, the scientists found, exhibited significant disruption in their lipid metabolism, leading to diminished nutrients in their blood and in their breast milk. As a result, their offspring showed significant growth and development deficits during the postnatal period before weaning. Birth outcomes such as litter size and length of gestation were unaffected.
“[W]e have to think again about whether 10 ppb arsenic as a U.S. drinking water standard is safe and protective of human health,” says author Dr. Joshua Hamilton, who is the MBL’s chief academic and scientific officer and a senior scientist in the MBL Bay Paul Center.
Current EPA Arsenic Standards Were Hard Fought
The 10 ppb arsenic standard went into effect in 2006 after a long, long regulatory process and a huge battle with the George W. Bush administration. The standard had previously been 50 ppb and new stricter regulations were near final when President Bush took office and blocked it in 2001. The ensuing battle over the costs and benefits of implementing the standards involved one of President Bush’s few congressional defeats in the early days of his administration.
The arsenic rule has a long and controversial history. A 50 parts per billion (ppb) arsenic standard was first adopted by the U.S. Public Health Service (USPHS) in 1942. Although USPHS recommended that the standard be dropped to 10 ppb in 1962, it was not until Congress ordered EPA three separate times to update the rule – and after NRDC sued EPA in 2000 – that the agency proposed the standard. The Clinton administration finalized it at 10 ppb in January 2001. A furor erupted after the Bush administration suspended the rule in March 2001. After public outcry, an NRDC lawsuit, and a National Academy of Sciences report (issued in September 2001) finding that EPA had substantially underestimated arsenic’s cancer risks, the Bush administration reversed course and allowed the new 10 ppb standard to stand.
One of the concerns of opponents to the new standard was the disproportionate costs to small water systems in naturally high-arsenic areas of the country and mining or farming communities with arsenic contamination from mine operations or pesticides. Even after the regulation was finalized mining and farming states sued and it took until 2003 to settle the lawsuits.
The 10 ppb standard itself was a political compromise. EPA under the Clinton administration initially proposed a standard of 3 ppb.
U.S. Arsenic Regulations May Not Protect Women and Babies
“[T]his study reiterates an emerging idea in toxicology that pregnant women and their offspring are uniquely sensitive to chemicals in their environment,” Hamilton says. “There is a special window of vulnerability for both of them.”
Arsenic may disrupt a pregnant and breastfeeding women’s metabolism, endangering her child and her own health. “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. Her body will basically ‘eat itself’ to provide for the baby,” explained Hamilton. That protective process didn’t work for the mice drinking low levels of arsenic in their water.
The arsenic-exposed mothers accumulate abnormal amounts of fat in the liver, something known as “fatty liver” disease, which is connected to metabolic syndrome (hypertension, diabetes, obesity, and high cholesterol). The health implications of this non-alcohol caused fatty liver disease on the mother is unclear. The developmental harm caused to their offspring was very clear. Within 10 days of birth, the pups of arsenic-exposed mothers were noticeably smaller than the control group. By 21 days, typical weaning for mice, the difference was dramatic.
“[W]e gave [mice] drinking water with arsenic in it with exactly the same dose that you can drink out of your tap that the EPA says is safe – and bad things happened to them,” Hamilton told Fox News. “It needs further investigation, but certainly it’s a cautionary tale that at such a low dose, we’re seeing these dramatic effects on these animals.
Thousands of Americans Drink Water With Even Higher Arsenic Levels
As many as 25 million Americans drink water from unregulated wells and so may drink water with an arsenic concentration that exceeds this level public tap water standards. “If you are on a private water system, particularly in a region with high arsenic, have your water tested so that you know what you are drinking,” suggested Dr. Hamilton.
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