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While high concentrations of arsenic are found mostly in the Western region of the United States, parts of the Midwest and New England show levels of arsenic
that exceed the newly approved U.S. Environmental Protection Agency (EPA) standard of 10 parts per billion (ppb). Individuals not willing to wait for their water system's compliance with the arsenic standard currently are looking for treatment systems to use in their homes. POU and even point-of-entry (POE) treatment systems are an attractive solution for these individuals. The process should begin with a basic understanding of arsenic contamination and the element's chemistry, a complete water quality analysis of the application-specific water and the knowledge of available technologies.
Editor’s Note: Part 1 of this series provided a timeline for the development of a drinking water standard for arsenic. It also summarized the political and public reactions to the U.S. EPA decision to delay and withdraw the arsenic rule.
Part 2 dealt with human exposure and advances in knowledge concerning human health effects of exposure to arsenic.
Part 3 summarized early data on the occurrence of arsenic in U.S. waters.
Arsenic Removal Methods
Only recently has a substantial amount of data become available on the concentrations of arsenic in United States drinking water supplies. Most of these data have been accumulated by the state regulatory agencies responsible for monitoring drinking waters. Since the arsenic standard has been 50 µg/L, some state agencies have recorded arsenic concentrations only in excess of that concentration. Others have been limited by the sensitivity of the analytical techniques and equipment used for the arsenic analysis. As a result, much of the available arsenic data are “below the limits of detection.
Occurrence of Arsenic in U.S. Waters
On November 26, 2001, the new arsenic standard was signed into law—lowering the acceptable level for the contaminant from 50 parts per billion (ppb) to 10 ppb. Approximately 4,100 municipal water systems serving nearly 13 million people nationwide are affected by the law and are required to meet compliance by January 2006. According to the U.S. Environmental Protection Agency (EPA), 97 percent of these systems are small systems serving fewer than 10,000 people each. The economic impact on these small systems is likely to be large. However, there currently are options available to small municipalities that may be more affordable than central treatment.
New POU Technologies May Be the Answer for Small Municipalities Facing High Costs
On-going health effects studies and research reports (2001) appear to support the argument for lowering the current EPA drinking water standard for arsenic. Studies conducted by EPA, the University of North Carolina and the University of British Columbia have indicated that methylated metabolites of trivalent arsenic are genotoxic. In other words, they damage DNA in human cells.
Human Exposure and Health Effects
In March 2001, the U.S. Environmental Protection Agency (EPA) withdrew a proposal for a lower maximum contaminant level (MCL) for arsenic in drinking water that would bring the standard from 50 parts per billion (ppb) to 10 ppb. At that time, the EPA commissioned three studies to examine the benefits, costs and health effects associated with a lower standard for arsenic.
A brief look at one solution for arsenic removal
Recent market research showed that more than 73 percent of consumers prefer to consult with a water treatment professional when dealing with arsenic. Combining this inclination with the preference for the POE approach, the treatment professional has a unique opportunity to generate significant new revenue from POE sales with minimal upfront effort.
After the U.S. Environmental Protection Agency (EPA) finally announced the new maximum contaminant level (MCL) of 10 parts per billion (ppb) for arsenic, an estimated 4,000 community water systems are now left to take measures to lower their arsenic levels, which were previously at 50 ppb.
The National Academy of Sciences, National Research Council (NAS-NRC) report was released on September 11, 2001. It concluded that the existing health effects data on arsenic essentially were sound. In addition, their review of three new epidemiological studies indicated that the health risks posed by arsenic in drinking water were greater than previously believed. As a result, in October, well before its self-imposed deadline, EPA rescinded its March implementation ban and endorsed the 10 µg/L arsenic MCL.
The Development of Drinking Water Regulations