GeoInsighter Fall 2002 Newsletter

The Ups and Downs of the Arsenic Drinking Water Standard

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In the Summer 2000 issue of the GeoInsighter (Volume 5, Number 2), we reported on the decision from the United States Environmental Protection Agency (USEPA) to reduce the arsenic drinking water standard from the former level of 50 parts per billion (ppb) to 5 ppb. Since that time, Bill Clinton left the White House, George W. Bush was elected, and the arsenic drinking water standard was revised again. The difficulty in establishing the standard is due to balancing the costs that would be required to update municipal drinking water treatment systems with the human health risk data for arsenic. 

Arsenic is a metallic element that typically impacts ground water through the erosion of arsenic-bearing rocks and minerals. Although arsenic is almost insoluble, small amounts of arsenic are released to ground water as the rock containing arsenic sulfides weathers and erodes. Because arsenic is derived from rock weathering, arsenic is typically encountered at higher concentrations in ground water than in surface water. Therefore, communities that rely upon ground water as a drinking water source (typically in western states, parts of the Midwest, and New England) will be more affected than communities that obtain their drinking water from lakes and rivers. Arsenic is also used in insecticides, herbicides, pesticides, in tanning animal hides, as pigment in paints, as a wood preservative, and as an ingredient in fireworks. 

The former arsenic drinking water standard of 50 ppb was set in 1975 based upon a Public Health Service standard originally established in 1942. As part of the 1996 revisions to the Safe Drinking Water Act, the USEPA was required to re-evaluate the former arsenic drinking water standard. Although the USEPA indicated that a drinking water standard of 3 ppb would be technologically feasible, they decided on May 24, 2000 to adopt a standard of 5 ppb rather than 3 ppb due to cost concerns associated with treatment. Shortly after George W. Bush entered the White House, the USEPA proposed, on January 17, 2001, to revise the arsenic drinking water standard to 10 ppb. The increase in the proposed standard was driven primarily by concerns from western states where the highest concentrations of arsenic-impacted ground water are present. Water suppliers in these states would have had to provide considerable funding to upgrade community drinking water plants.

The increase in the proposed standard from 5 ppb to 10 ppb was very controversial among environmental and consumer groups that were concerned about potential increases to health risks. Due to the strong criticism, on March 20, 2001 the USEPA proposed to withdraw the proposed standard of 10 ppb and solicit an independent review of potential standards. The USEPA asked the National Academy of Sciences and the National Drinking Water Advisory Council, as well as the USEPA’s Science Advisory Board, to evaluate the costs and benefits of arsenic standards of 3 ppb, 5 ppb, 10 ppb, and 20 ppb. At the conclusion of the review, USEPA Administrator Christie Whitman announced on October 31, 2001 that the arsenic standard in drinking water will be 10 ppb. The arsenic drinking water standard of 10 ppb became effective on February 22, 2002.

The USEPA estimates that nearly 97 percent of the community water supply systems that are affected by this standard serve less than 10,000 people each. Due to the costs associated with upgrading treatment systems, particularly for small water supply systems, the USEPA is providing $20 million in funding over the next two years for research and development of cost-effective technologies in treating arsenic in ground water. In addition, community water systems have until January 2006 to meet the new standard.

Kevin D. Trainer, P.G
kdtrainer@geoinc.com

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