Environmental ▼News More chloramine complications
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utilities to use chloramines and other alternatives to chlorine disinfection. But the new EPA study and other data indicate that alternative disinfectants may encourage the formation of new toxicologically significant DBPs, he says.
In mammalian cells, IA is by far the most potent DBP tested, says Plewa. The DBP most toxic to bacteria, dichloromethylhydroxyfuranone, a chlorinated furanone commonly known as MX, is 80 times more potent than IA as a mutagen in bacteMICHAEL J. PLEWA
lternatives to drinking-water chlorination, such as chloramines, may produce increased concentrations of disinfection byproducts (DBPs) with toxicities far more potent than those currently regulated, according to research published in this issue of ES&T (pp 4713–4722). The research was inspired by a 2002 drinking-water survey conducted by the U.S. EPA, which revealed that iodide-containing compounds were forming in some drinking water at concentrations on the order of 10 micrograms per liter (µg/L). The water came from a utility where source waters with high levels of bromide and organic matter were disinfected with chloramines. Finding the iodinated DBPs was “totally unexpected,” says Susan Richardson, a chemist with EPA’s Ecosystems Research Division lab in Athens, Ga., and head of the 2002 survey. Now, University of Illinois toxicologist and corresponding author Michael Plewa, together with Richardson and colleagues, has identified some of the specific iodinated DBPs and reports that one, iodoacetic acid (IA), is the most genotoxic to mammalian cells of any DBP ever identified. The findings suggests that the switch in drinking-water disinfectants may cause increased adverse health effects in the U.S. population, says Plewa, who notes that current EPA regulations are based on limited toxicological and chemical knowledge. Water companies have been adopting chloramines and other chlorine-alternative disinfection strategies to comply with the first part, or stage, of EPA’s 1998 DBP rule, because chloramines, a mixture of chlorine and ammonia, dramatically reduce levels of regulated DBPs. Part 2 of the DBP rule further encourages drinking water
Elizabeth Wagner (foreground) and Kristin McCalla are two of the University of Illinois scientists evaluating the byproducts generated when chloramines are used to disinfect drinking water. One of the tests for characterizing the toxicity of these byproducts uses Chinese hamster ovary cells (inset).
At least one organization, the National Rural Water Association (NRWA), is urging EPA to delay implementing the stage 2 DBP rule because these studies point to unforeseen consequences. “There is significant uncertainty around the health impacts of these iodinated DBPs—the changes initiated by stage 2 could actually make the health problem worse,” says Mike Keegan, an NRWA analyst in Washington, D.C. The stage 2 rule is set to be finalized next year, and EPA does not intend to delay the rule, according to environmental engineer Stig Regli at EPA’s Office of Water in Washington, D.C.
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ria, as measured by the Ames test. But in mammalian cells, IA is 93 times more cytotoxic than MX and 28 times more mutagenic. Because mammalian cells are more indicative of effects in humans, Plewa concludes that IA is likely to be more hazardous to humans. IA is particularly toxic to mammalian cells because it inhibits cellular detoxification mechanisms, he says. Drinking-water sources with high bromide concentrations often also contain iodide, since both usually come from a saltwater source. The source of this saline water can be either saltwater intrusion into coastal fresh water or “connate © 2004 American Chemical Society
DBP or mixture of DBPs responsible for the risk has yet to be identified, according to research chemist Stuart Krasner with the Metropolitan Water District of Southern California in LaVerne, Ca. It’s unlikely that iodinated DBPs could be the culprit, because epidemiological studies show that people who drink chloraminated waters have a lower risk for those cancers than those who drink chlorinated water, says Regli. Krasner, a coauthor of the 2002 study, agrees with Regli. The iodinated DBPs typically occurred at submicrogram-per-liter levels, except for the one utility in the nationwide survey that had about 10 µg/L of iodinated trihalomethanes (THMs), he says. The utilities included in the survey were chosen to be representative and highlight the worst-case situations. The stage 2 DBP rule is likely to prompt many surface water plants to switch to chloramines. But in many cases, utilities will be using chloramines for secondary disinfection during distribution, not for primary disinfection at the plant, says Krasner. “Ultimately, it will be important to know the levels at which these iodo-acids occur, in order to assess the potential for adverse environmental and human health risks,” says Plewa. Richardson is currently working on a project to acquire those data. —REBECCA RENNER
Microarrays monitor environmental contaminants In one of the first environmental applications of microarray technology to invertebrates, researchers at the Pacific Northwest National Laboratory (PNNL) in the U.S. are developing a process based on chip technology to scan for genes in midges, gnat-like flies, that respond to specific pollutants. The advantage such an array offers for biomonitoring is that it can survey for many contaminants as well as their
sources, the researchers note. According to Ann Miracle, a research biologist with the U.S. EPA’s Office of Research and Development, scientists are interested in developing any model organism system that would be robust enough to provide data relevant to different populations or various combinations of stressors. “It’s sort of the holy grail right now because there isn’t a good system out there,” she
News Briefs GHG emissions decline Numbers released from the European Environment Agency show that the European Union (EU) is closer to meeting an overall 8% decrease in greenhouse gases (GHGs). Base levels were established in 1990, and the target date for reduction is 2012. However, according to the annual report on GHGs, only France, Germany, Sweden, and the United Kingdom are on track to meet their individual goals. EU GHG emissions fell mostly because of warm winters and an economic slowdown, says the report. However, member states have also cut nitrous oxide discharges from the chemical industry and reduced methane releases from waste and landfills. For details of the July report, go to http://reports.eea.eu. int /technical_report_2004_2/en.
Linking PM and health The University of Washington has been awarded the U.S. EPA’s largest scientific research grant to date to study the association between ambient fine particulate matter (PM) and cardiovascular disease. EPA’s Science to Achieve Results (STAR) program of competitive grants will fund the $30 million grant awarded in July. Joel Kaufman, associate professor in the School of Public Health and Community Medicine, will lead the study. During the next 10 years, researchers from several of the university’s departments will track 8700 people aged 50–89 and belonging to various ethnic groups, who live in cities across the country. Specifically, the researchers will look at factors associated with heart disease. For more information, visit www.epa.gov/ pmresearch/pm_grant.
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water” locked away underground from a time in the geological past when ocean waters covered a region. For example, the high concentrations of iodinated DBPs in the national survey came from a source affected by connate waters. Chloramination favors the formation of iodinated DBPs in such waters because chloramines, with less oxidizing power than chlorine, allow hypoiodous acid to accumulate and react with organic matter to form them, according to Swiss Federal Institute for Environmental Science and Technology (EAWAG) chemist Urs von Gunten, who has studied the kinetics of these reactions (Environ. Sci. Technol. 1999, 33, 4040–4045). Some of the iodinated DBPs may be significantly more toxic than those that we are currently aware of, agrees Regli. But it’s unlikely they pose a significant health risk, because it takes a rare set of conditions to produce them in significant quantities, he says. “The 2002 national study targeted extreme water—with extremely high levels of bromine and natural organic matter. As such, the finding is unlikely to affect a great number of people,” he says. Epidemiological studies have linked chlorinated drinking water from surface sources with a higher risk of bladder and colorectal cancers, and DBPs are the most likely culprit. But to date, the particular
