EPA considering quick action on Cryptosporidium
E
PA is discussing whether to act quickly to reduce the risk posed by Cryptosporidium in drinking water, says William Diamond, director of the Drinking Water Standards Division in the Office of Groundwater and Drinking Water. Currently, Cryptosporidium is not covered under the surface water treatment rule (SWTR) of the Safe Drinking Water Act, but the 1993 outbreak in Milwaukee, which affected an estimated 400,000 people, has put pressure on the Agency and the water suppliers to act. Last year, the Agency proposed to toughen the SWTR to address Cryptosporidium and increase controls on other microbes (Federal Register, 1994, 59, 38832). What has become known as the enhanced SWTR (ESWrR) sets a maximum contaminant level goal for Cryptosporidium of zero. However, final approval of ESWTR is tied to a rule mandating the monitoring of source waters by
Regulatory strategies under discussion for Cryptosporidium (green circles) in drinking water include mandatory and voluntary measures (positive control photomicrograph, using epifluorescence and differential interference contrast optics).
certain drinking-water utilities for Cryptosporidium, other microbes, and disinfection byproducts (see p. 20A). As a result, the comment period for the proposed ESWTR runs to May 30, 1996, and thus any action on ESWTR is more than a year away. According to Diamond, experts within the Agency, academia, and industry have suggested that EPA take additional steps; they view early action as risk reduction. "We are considering whether [that action] should be mandatory or whether states and the industry could work together." The latter approach could be set in motion, says Diamond, much faster than the regulatory route. Alan Roberson, who directs regulatory affairs for the American Water Works Association (AWWA), says that he sees EPA moving toward a standard guidance. Before the November election, according to Roberson and sources within EPA, the Agency was leaning toward issuing a regulation this summer. However, EPA has now backed away from that position, says Roberson. AWWA has already issued its own guidelines, recommending that finished drinking water consistently measure 0.5 NPU (nephelometric turbidity units) and that utilities set a goal of 0.1 NPU (but without time values) (see ES&T, November 1994, p. 509A). Current regulations impose a value of 0.5 NPU to be met 95% of the time in finished water. Roberson expects that EPA's eventual action will parallel AWWAs approach. The utilities most likely to be affected, predicts Roberson, are those that serve 100,000 or more people and use surface water or surface-fed groundwater. Because Cryptosporidium is found in surface waters as biolog-
ical particles measuring about 5 microns, turbidity is currently the best indicator of the microbe's presence on a daily basis. Analytical methods that directly identify Cryptosporidium take days to complete. Tougher turbidity standards are expected to improve the removal of these biological particles through filtration or tighter controls on source waters. Standard chemical disinfection, such as chlorination, is ineffective against Cryptosporidium. "Ozonation shows some promise, but we really don't have a magic bullet against Cryptosporidium," reports Richard Karlin of AWWAs Research Foundation (Denver, CO). The pathogen is spread via farm runoff, municipal sewage wastes, and wild animal feces. Surveys of cattle show high rates of infection. Moreover, says Karlin, the microorganism appears to be already fairly widespread in raw surface waters. In addition, Cryptosporidium can survive for months in soil under certain conditions. Because it is still uncertain whether these tougher measures will prevent future outbreaks, there is great concern about what to do if Cryptosporidium or any other pathogen is detected or suspected of being in drinking water. (According to EPA, Cryptosporidium has been implicated in at least five outbreaks of gastroenteritis in the United States and as many as seven in the United Kingdom since 1983.) In the Milwaukee outbreak, individuals with weakened immune systems (such as AIDS patients) suffered the most from the pathogen. A number of deaths also were attributed to the outbreak. Currently there is no drug to treat Cryptosporidum infection in humans. EPA, the Centers for Disease Control, and the Food and Drug Administration are drawing up guidelines on when to issue warnings and whom should be warned. —ALAN NEWMAN
VOL. 29, NO. 1, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY • 1 7 A
