The arsenic argument
The EPA and Congress debate the drinking water standard for an infamous carcinogen.
Its always a pleasure when the folks inside the Beltway provide a solution to your problem. It makes you feel like your government truly is working for you. I originally planned to write an update on the Safe Drinking Water Act (SDWA) as amended in 1996 (see Todays Chemist at Work, Feb 1997). Unfortunately, the article promised to be a technical piece filled with arcane minutiae about funding, EPA authority, groundwater protection, and so on. I dont mean to trivialize or demean the importance of the SDWA, but it is difficult to build excitement for the topic. Then, suddenly and with little warning, on March 20, EPA Administrator Christine Whitman provided my deliverance by announcing that the Drinking Water Standard for Arsenic [a.k.a. the arsenic in drinking water rule (66 CFR 6976, Jan 22, 2001)], issued in the last months of the Clinton administration, was being delayed because the scientific evidence was not sufficient to justify the compliance costs drinking water suppliers would face. The promulgation of the rule for arsenic was mandated by Congress in the 1996 amendments to the SDWA, which stated that the EPA had to develop a plan to research the effects of low-level arsenic exposure and finalize a rule no later than January 1, 2001. Administrator Whitman later extended this delay to February 2002 to allow for a reassessment of the rule in conjunction with the National Academy of Sciences and the National Drinking Water Advisory Council.
|Is There Arsenic in Your Drinking Water?
By law, your local water utility is required to make available a report on all contaminants in your drinking water. You can call your local water utility and request the report if it has not been mailed to you. (The EPAs drinking water hotline at 800-426-4791 can assist you in locating your water supplier or state drinking water agency.) This map is modified from U.S. Geological Survey monitoring data and shows counties where arsenic was greater than 3 ppb in those counties sampled. A complete survey of U.S. drinking waters for arsenic has yet to be done.
Source: Welch, A. H.; et al. Arsenic in Ground Water Sources of the United States: U.S. Geological Survey Fact Sheet 063-00, 2000, p 4.
The adverse properties of arsenic compounds, or arsenicals, have been known for more than 2000 years. Arsenic has come to be considered almost synonymous with poison and cancer. Much of our current awareness can be traced to the 1944 movie classic Arsenic and Old Lace, starring Cary Grant as Mortimer Brewster, a newspaperman who discovers that his kindly aunts have been poisoning their gentlemen callers with arsenic. Emperors, kings, arctic explorers, and commoners have been treated with arsenicals for both legitimate and murderous purposes: Nero is thought to have poisoned Britannicus with it in 55 AD; Hippocrates is said to have used arsenicals to treat ulcers. Further, arsenicals have had important medical uses in the treatment of sleeping sickness, syphilis, tuberculosis, and skin diseases. In fact, the compounds enjoyed such widespread use in embalming during and after the Civil War that today, arsenic leaching from old cemeteries is a known groundwater pollutant. Additionally, arsenic plays an important role in modern technology as an essential component of semiconductor devices, principally in the form of gallium arsenide.
In the early 1800s, arsenic exposure was linked to cancer and its medicinal use diminished. However, recent clinical research has shown that arsenic trioxide, administered intravenously, can induce cancer remission in some people with refractory acute promyelocytic leukemia; the FDA subsequently approved this treatment for use beginning in September 2000. Further, the U.S. Department of Agriculture (USDA) is currently investigating the beneficial role of arsenic in the human diet. It now appears that it may be essential in human nutrition and that too little in the diet may actually increase cancer risks (1). Such is the yin and yang of arsenic.
The arsenic rule (2) lowers the maximum contaminant level (MCL, the legally enforceable limit for drinking water contaminants) for arsenic in drinking water from 50 ppb to 10 ppb. To justify lowering the MCL, the EPA had to conduct a risk assessment analogous to that done for pesticides and a costbenefit analysis. Arsenic is unique in that its risk assessment relies entirely on human data. (Common laboratory animals used for carcinogenic bioassays metabolize arsenic via a different pathway than humans.) However, there is little or no doubt that inorganic arsenic, such as arsenic trioxide, is a human carcinogen. (The EPA classified orally ingested inorganic arsenic as a human carcinogen in 1984.)
Numerous worldwide studies of human populations exposed to arsenic in drinking water have shown a clear doseresponse relationship with increased incidence of skin, lung, and bladder cancers, albeit at exposure levels much higher than the current U.S. MCL (see sidebar, Heavy Metal in Bangladesh). As a result, the World Health Organization lowered the long-standing 50-ppb international guideline limit to 10 ppb. Additionally, the U.S. National Academy of Sciences (NAS), in its 1999 report, Arsenic in Drinking Water (3), supported lowering the MCL; the NAS study estimated that the combined cancer risk from a lifetime exposure of 50 ppb in drinking water could be as high as 1 in 100! Assuming a linear extrapolation to reach a cancer risk of 1 in 1 million (the level commonly used for pesticide-related health assessments), the MCL would have to be lowered to 5 pptan obviously ludicrous goal given the natural prevalence of arsenic in the environment. The NAS concluded, The current EPA MCL for arsenic in drinking water of 50 ppb does not achieve EPAs goal for public health protection and, therefore, requires downward revision as promptly as possible.
|Heavy Metal in Bangladesh
|The current arsenic crisis in Bangladesh and West Bengal in India is proving to be the largest mass poisoning of a human population in history. Upwards of 70 million people have been exposed to toxic levels of arsenic in drinking water obtained from wells drilled by various international aid agencies during the 1980s in an ironic attempt to switch the population from contaminated surface water to safe groundwater. Tragically, if the wells had been more than 100 meters deep, the crisis would have been averted. Today, however, many people show prominent signs of arsenicosis, such as hyper- or hypo-pigmentation and/or keratoses on the hands and feet. It now is expected that the incidence of skin cancers will increase, to be followed by lung, liver, kidney, and bladder cancers (4).
New Goals Set
In June 2000, as a result of its risk and costbenefit analyses, the EPA initially proposed lowering the MCL to 5 ppb before settling on a 10-ppb standard in the final rule. Further, the EPA established a health-based, nonenforceable MCL Goal (MCLG). This goal established the arsenic level at 0 mg/L; the MCL is set as close as possible to the MCLG.
The EPA estimates that the rule with an MCL of 10 ppb would affect approximately 74,000 water systems and that 4100 systemsserving 13 million peoplewould have to take corrective action to comply. (Of the affected systems, however, 97% serve fewer than 10,000 people.) Compliance costs for this rule are projected to range from $38 to $327 per household, or a collective annual total of $200 million by the year 2006.
Thus, the three different federal agencies involved have reached different conclusions about the link between arsenic and cancer: The FDA approves arsenic to cure cancer; the USDA thinks it may be essential to prevent cancer; and the EPA thinks trace levels cause cancer. Furthermore, the significance of cancer risk is viewed through different glasses within the EPA. The agencys Office of Pesticide Programs views approval of a pesticide with a cancer risk of greater than 1 in a million with, to say the least, a great deal of skepticism, whereas the Office of Ground Water and Drinking Water seems comfortable with cancer risks maintained at orders of magnitude far greater.
Is arsenic in U.S. drinking water a significant contributor to our cancer rates? Sadly, aside from anecdotal news reports, little scientific study has been conducted using U.S. sources. The EPA has been forced to rely almost exclusively on studies from Taiwan, Argentina, Chile, or other foreign locations whose populations have a different socioeconomic and nutritional status than that of the United States.
The Future for Arsenic Levels
Health and environmental groups have been actively supporting a serious reduction in the MCL and have already increased pressure on both Congress and the administration to act. Congressional Democrats and moderate Republicans have made clear to the Bush administration that they are unhappy with the delay. On the other hand, President Bush has publicly committed to more study, then less arsenic, and EPA Administrator Whitman has announced that the EPAs review process will consider a range of MCLs from 3 to 20 ppb.
On July 28, however, a setback for the Bush administrations environmental agenda emerged as the Republican-controlled House voted 218 to 189 to attach an amendment forcing the reinstatement of the Clinton administrations 10-ppb standard to a $113 billion appropriations bill that contains monies for veterans, housing, and the EPA. If Congress passes the bill, President Bush might find it politically difficult to veto. Only time will tell.
- Uthus, E. O. ArsenicBad, good or both? Grand Forks Human Nutrition Research Center: www.gfhnrc.ars.usda.gov/News/nws9710a.htm.
- The Drinking Water Standard for Arsenic, EPA 85-F-00-015: www.epa.gov/ogwdw000/ars/ars_rule_factsheet.html.
- Arsenic in Drinking Water; Subcommittee on Arsenic in Drinking Water, National Research Council; National Academy Press: Washington, DC, 1999; http://books.nap.edu/books/0309063337/html/index.html.
- The West Bengal and Bangladesh Arsenic Crisis Information Centre, www.bicn.com/acic/
Roger A. Novak has a Ph.D. from the University of Houston and is a chemical consultant. Send your comments or questions regarding this article to firstname.lastname@example.org or the Editorial Office 1155 16th St N.W., Washington, DC 20036.