FEATURE
Growing Concern About Disinfection Byproducts EPA is under increasing public pressure to assess potential short-term health risks of chlorinated drinking water. KELLYN
T
he challenge of balancing the benefits of disinfecting drinking water against its risks is likely to grow considerably more complicated in the coming years. It took EPA decades to craft comprehensive rules attempting to ensure that drinking water utilities don't inadvertently increase consumers' risk of contracting cancer by adding disinfectants which are introduced to decrease the chance that disease-causing microbes end up in the tap water Now the new issue of possible short-term health risks may signifirantly complicate the alreaHv m m p l p v dphate about how to hpst
safeguard the nation's water sunnlv This year, determining whether there are shortterm health consequences from exposure to drinking water disinfection byproducts became a "public health priority," said Chris Wiant, director of the Tri-County Health Department in Denver, Colo. The prospect of regulating DBPs, based on their potential association with birth defects and miscarriages, was a subject of discussion at the annual meeting of the American Water Works Association this June, where a group of water utility representatives, public health specialists, regulators, and environmentalists all agreed it was a distinct possibility The prospect of further regulation "has profound implications," summarized Edward Means, deputy general manager of the Metropolitan Water District of Southern California. Regulations to curtail the short-term consequences of DBP exposure 5 4 6 A • DEC. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
BETTS could dramatically change the way water utilities and consumers cope with contaminants that are unintentionally generated in the disinfection process, noted people involved in the drinking water industry. It could greatly increase the monitoring burden on drinking water utilities, they said. It could result in more stringent limits on a wider range of DBPs and induce EPA to begin publishing advisories that pregnant women should not drink t a p watPT
Disinfection pros and cons Since 1908, chlorine has been used to treat drinking water to remove pathogenic bacteria such as typhus and cholera (1), and most drinking water utilities in trie United States still disinfect their water with chlorine or chloramines, said Stig Regli, an environmental engineer with EPAs Office of Groundwater and Drinking Water. Disinfection has significantly reduced the population's short-term risk of contracting a microbial disease. Disinfection with chlorine or chloramines is responsible for vastly reducing the risk of death from several per hundred thousand (for typhoid and cholera in the late 1890s and early 1900s) to virtually no occurrences of these diseases today. However, hundreds of chlorinated hydrocarbons—a few are known to be carcinogenic (i)— form when chlorine reacts with naturally occurring organic material in the water. Chloramines tend to result in the same DBPs as chlorine, albeit in lower concentrations, said Fred Hauchman, assistant di0013-936X/98/0932-546AS15.00/0 © 1998 American Chemical Society
rector for water at EPA's National Health and Environmental Effects Research Laboratory. A variety of DBPs, including some associated with health risks, are also generated by chlorine dioxide and ozone, both of which are popular disinfection alternatives in the United States, Hauchman noted. The most recent impediment to EPA's efforts to balance these pros and cons with regulation was raised two years ago when problems associated with the microbial pathogen Cryptosporidium surfaced. There is a push now for more effective disinfection to lower the risks of Cryptosporidium and Giardia in public water supplies. Despite these new concerns, the long-awaited "stage-1" DBP rules finally took effect in November. The new regulations greatly broaden the agency's efforts to reduce the long-term risk of developing cancer from drinking tap water. Prior to last month, only four DBPs were regulated based on an interim rule issued in 1979 in response to public concern over the potential cancer-causing effects of chloroform, a probable human carcinogen that is known to affect liver and kidney function. Chloroform is one of four trihalomethane chemicals (chloroform, dibromochloromefhane bromodichloromethane, bromoform) regulated as "total t r i h a l o m e t h a n e s " (TTHMs). In addition to chloroform EPA has listed bromodichloromethane and bromoform as probable human carcinogens (2) Because they are regularly measured TTHM levels are now commonly used as a surrogate for DBPs in drinking water In addition to decreasing the maximum allowable contaminant level (MCL) for TTHMs by 20% to 80 micrograms/Liter (ug/L), the new rules allow the agency to begin regulating three other compounds suspected of causing health problems—haloacetic acids, bromate, and chlorite—as DBPs. Because some disinfectants are also suspected to be toxic at higher concentrations, the stage-1 DBP rule also set limits for the amounts of chlorine, chloramines, and chlorine dioxide that can be present in drinking water. None of the regulations that EPA has crafted are intended to address potential short-term risks from DBP exposure, however. "The whole idea of DBP regulation since the 1970s has been that [DBPs] were thought to be a problem only if you were exposed to high levels over long periods of time," said Erik Olson, a drinking water specialist for the Natural Resources Defense Council.
Burgeoning research interest Recently, the number of published studies pointing toward an association between DBPs and reproductive problems has grown. More than a half dozen studies now suggest a possible link between elevated levels of TTHM and a variety of adverse reproductive outcomes, including miscarriage {3-7), impaired fetal growth {5-8), and certain birth defects (6, 7, 9). A study of more than 5000 women published this March by the California Department of Health Services (3) suggests an increased risk of firsttrimester miscarriages among women who daily consume more than five glasses of cold tap water in which the TTHM level exceeds 75 ug/L. This level is
comparable to the reduced MCL of 80 ug/L mat took effect last month and is below the 100 ug/L level in effect since 1979. The fact that women were recruited for the study on learning they were pregnant bolstered the public's perceived importance of the study. In August, EPA and the American Water Works Association Research Foundation (AWWARF) announced that they were funding a three-year, $3million study to replicate the California Department of Health Services' study. On the basis of the data available, however— including prepublication data from the California Department of Health Services study—an EPA panel concluded there is not yet "convincing evidence that DBPs cause adverse pregnancy outcomes" {10). The panel recommended that EPA continue epidemiological research on the subject, including the scheduled replication of the California study. "The research certainly provides a strong basis, motivation, and justification for future research," stressed Hauchman of EPA's National Health and Environmental Effects Research Laboratory.
Setting the stage At this point, it is quite possible that the potential shortterm health risk issue will make its way into the negotiations over the next round of DBP rules, said Regli. Though these "stage-2" negotiations are already under way, they are not expected to intensify until next spring. The new issue could turn the negotiations "completely on their head," predicted Olson. The disinfection byproducts issue could motivate a reappraisal of how much DBPs people are exposed to, and through which routes. Previously, studies ascertaining the risks of DBP exposure focused only on drinking water. More recent studies account for other routes of exposure, such as through showering and hand-washing, routes of dermal exposure that are not generally controlled by drinking bottled water or by point-of-use devices on kitchen faucets, Olson said. The amount of TTHMs—and, by association, DBPs as a whole—to which a tap water user is exposed fluctuates depending on temperature, amount of residual chlorine, and a person's location within the distribution system, said Michael Cox, a toxicologist in the Office of Groundwater and Drinking Water. Regli noted that it is not unusual for a utility to draw samples that exceed the MCL in the summertime. The traditional approach of averaging annual TTHM levels based on quarterly samples therefore masks the fact that people can be exposed to DBP levels that vary significantly from the reported figures Olson said. Further complicating the issue, only a small number of the hundreds of DBPs found in drinking water have been studied by EPA. "Half of the DBPs are not characterized," said Jeffrey Griffiths, a professor of public health at Tufts University. "What I'm worried about is that since we don't know what else is out there, we're going to miss a bad actor," he commented. "We certainly haven't evaluated many of the DBPs," Hauchman acknowledged, "but to be of concern, the DEC. 1, 1998 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 5 4 7 A
contaminant has to have an effect at environmentally relevant concentrations. We're still basically finding effects only at levels in these toxicology studies that are orders of magnitude away from environmental levels." The agency is currently working with the National Toxicology Screening Program to conduct a series of studies to look at reproductive and developmental endpoints of a number of individual DBPs, he said. Hauchman noted that one area of potential concern yet to be evaluated by toxicologists is the effect of being exposed to mixtures of DBPs. Utilitarian consequences If EPA ultimately decides to regulate DBPs based on short-term health concerns, the result could financially burden utilities, noted Cox. He mentioned the potential effect that regulation could have on smaller systems—more than 90% of the nation's 55,000 community drinking water systems serve fewer than 10,000 people. Utilities would have to monitor DBP levels more frequently, he said, which requires additional time and manpower if the utility has its own laboratory, and additional expenses, if A n EPA panel the utility must send samples out for analysis. Cox said such reguconcluded lation could make notifying consumers of violations more of a there is not yet challenge for utilities. convincing Current DBP regulations require that a utility's annual averevidence that age DBP concentrations be below the MCL level. But, Olson noted DBPs cause that DBP spikes—short-duration concentration elevations— adverse can occur. He mentioned data that indicated summertime pregnancy TTHM levels ranging between 10 outcomes. and 150 ug/L on the same day within the same city and expressed concern. Because DBP levels can fluctuate, requiring utilities to keep drinking water contaminant concentrations below the MCLs at all times could require utilities to make "major process changes " said Alan Roberson director of regulatory affairs for AWWA He suggested that such requirements might motivate 2040% of the water utilities to embrace alternative disinfectants particularly those using surface water Olson suggested that a "multiple barrier" approach that combines strong source water protection programs with advanced treatment technologies such as ozone or granular activated carbon might simultaneously reduce both microbial and DBP risks. But the cost to implement such an approach is "not trivial," he acknowledged. Switching to alternative disinfectants is by no means a guarantee that there will be a decrease of short-term health effects, if indeed they are real. There are limitations to all of the known methods of disinfection, and all chemical disinfectants produce byproducts. For no disinfectant or combination of disinfectants have all of the DBPs been identified and, therefore, tested by toxicological methods. 5 4 8 A • DEC. 1, 1998/ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
Rather than trying to further reduce the amount of DBPs in drinking water, Roberson suggested that it might be more cost-effective for utilities to simply advise women not to drink tap water during the first three months of their pregnancies, perhaps even providing them with bottled water. "It's a public health decision," he said and noted that the odds of having a child with birth defects are "an order of magnitude higher" for women who do not take folic acid supplements during their pregnancy. "I'm not convinced that you need to have sparkling clean water in your toilet," he remarked, noting that, per car)~ ita, Americans drink only a very small percentage of the 125 gallons of tap water they use each day It is not clear how broadly the stage-2 DBP rules could be affected by the discussion over the shortterm health consequences of DBP exposure. The rules will be negotiated in 1999 and proposed in 2000, before data from the EPA-AWWARF DBP health effects study will be available. However, Regli said that the agency is considering the possibility of adding an evaluation of drinking water effects into an ongoing epidemiological study. This could provide data sufficiently quickly that could be considered when the rule is proposed, he said. Although the controvery raised in this DBP health effects debate could presage major changes in water treatment, it also frames water treatment progress. "The best measure of society is how well we protect our most vulnerable people: children, those who are immunocompromised, and pregnant women," said Olson. "What's supremely ironic," said Means, is that this issue has arisen at a time when the utilities have "never [before] invested more dollars, more time, [and] more energy into more highly sophisticated levels of treatment." References (1) Moeller, D. W. Environmental Health, rev. ed.; Harvard University Press: Cambridge, MA, 1997; p. 127. (2) Fed. Regist. 1994, 59, 38,699-38,704. (3) Waller, K.; Swan, S. H.; DeLorenze, G.; Hopkins, B. Epidemiology 1998, 9(2), 134-140. (4) Savitz D. A.; Andrews K. W; Pastore L. M. Environ. Health Perspect. 1995, 103, 98-103. (5) Kramer, M. D.; Lynch C. F.; Isacson, R; Hanson, J. W. Epidemiology 1992, 3, 407—413. (6) Bove, F. J.; et al. Report on Phase IV-B: public drinking water contamination and birth weight, and selected birth defects: A case-control study. New Jersey Department of Health: Trenton, N.J., 1992. (7) Bove, F. J.; Fulcomer, M. C; Klotz, J. B.; Esmart, J.; Dufficy, E. M.; Savrin, J. E. Am. J. Epidemiol. 1995, 141, 850862. (8) Gallagher, M. D.; Nuckols, J. R.; Stallones, L.; Savitz, D. A. Epidemiology 1998, 9, 484-489. (9) Klotz, J. B.; Pyrch, L. A.; Haltmeier, E; Trimbath, L. A casecontrol study of neural tube defects and drinking water contaminants; PB98-111644; Agency for Toxic Substances and Disease Registry: Atlanta, GA, January 1998. (10) Wilcox, A.; Aschengrau, A.; Daniel, R; Hatch, M.; Krasner, S. EPA Panel Report and Recommendations for conducting epidemiological research on possible reproductive and developmental effects of exposure to disinfected drinking water. National Health and Environmental Effects Research Laboratory: Research Triangle Park, NC, Feb. 12, 1998.
Kellyn S. Betts is an Associate Editor of ES&T.
