Arsenic

Arsenic is a naturally occurring chemical element found in rock and soil and is present in trace amounts in groundwater. Due to it's extreme toxicity, even in low doses arsenic exposure can pose a significant threat to human health.

In 2000, the U.S. EPA proposed lowering the Maximum Contaminant Level (MCL) for arsenic in drinking water to 5 ppb (parts per billion) replacing the old standard of 50 ppb, set back in 1942. According to the U.S. Geological Survey's National Water Quality Assessment Program database, water yfrom almost half of the 809 Arizona wells included exceeds 5 ppb arsenic. The Arizona Geological Survey reported that this new proposed standard would result in closure of many Arizona wells or require implementation of expensive remediation technology, with likely significant increase in the cost of water to many consumers.

The EPA adopted a new drinking water standard of 10 ppb in 2001.

Current research suggests that the new EPA drinking water standard may still be too high. A Study by a team of researchers at Dartmouth Medical School shows that in cell cultures extremely low levels of arsenic act as an endocrine disruptor. Endocrine disruption is likely to be an important contributor to arsenic's ability to increase risk of a host of diseases including several forms of cancer, heart disease, diabetes, and reproductive or developmental problems. Joshua Hamilton, PhD, professor of pharmacology and toxicology at Dartmouth advised that he "would hope the arsenic drinking water standard could be revisited."

The EPA Maximum Contaminant Level Goal (MCLG) for arsenic is zero.

SOURCES:

Dartmouth-Hitchcock Medical Center
Study - New Arsenic Levels May Still Be Toxic

Arizona Geological Survey - www.azgs.state.az.us/
Arsenic in Ground Water

ADEQ - Arizona Dept. of Environmental Quality
Arsenic Fact Sheet for Consumers

University of Arizona Cooperative Extension
Arsenic in Drinking Water Publication

U.S. Environmental Protection Agency (EPA)
Arsenic in Drinking Water

World Health Organization
Arsenic in Drinking Water

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