Byproduct of water disinfection process found to be highly toxic

A recently discovered disinfection byproduct (DBP) found in U.S. drinking water treated with chloramines is the most toxic ever found, says a scientist at the University of Illinois at Urbana-Champaign who tested samples on mammalian cells.

The discovery raises health-related questions regarding an Environmental Protection Agency plan to encourage all U.S. water-treatment facilities to adopt chlorine alternatives, said Michael J. Plewa [PLEV-uh], a genetic toxicologist in the department of crop sciences. "This research says that when you go to alternatives, you may be opening a Pandora's box of new DBPs, and these unregulated DBPs may be much more toxic, by orders of magnitude, than the regulated ones we are trying to avoid."

Plewa and colleagues, three of them with the EPA, report on the structure and toxicity of five iodoacids [EYE O-doe-acids] found in chloramines-treated water in Corpus Christi, Texas, in this month's issue of the journal Environmental Science & Technology. The findings, which appeared online in advance, already have prompted a call from the National Rural Water Association for a delay of EPA's Stage 2 rule aimed at reducing the amount of previously identified toxic DBPs occurring in chlorine-treated water.

"The iodoacids may be the most toxic family of DBPs to date," Plewa said in an interview. One of the five detailed in the study, iodoacetic acid, is the most toxic and DNA-damaging to mammalian cells in tests of known DBPs, he said.

"These iodoacetic acids raise new levels of concerns," he said. "Not only do they represent a potential danger because of all the water consumed on a daily basis, water is recycled back into the environment. What are the consequences? The goal of Stage 2 is to reduce DBPs, particularly the ones that fall under EPA regulations, and especially the ones that have been structurally identified and found to be toxic."

The use of chloramines, a combination of chlorine and ammonia, is one of three alternatives to chlorine disinfectant, which has been used for more than 100 years. Other alternatives are chlorine-dioxide and ozone. All treatments react to compounds present in a drinking water source, resulting in a variety of chemical disinfectant byproducts.

Some 600 DBPs have been identified since 1974, Plewa said. Scientists believe they've identified maybe 50 percent of all DBPs that occur in chlorine-treated water, but only 17 percent of those occurring in chloramines-treated water, 28 percent in water treated with chlorine-dioxide, and just 8 percent in ozone-treated water. Of the structurally identified DBPs, he said, the quantitative toxicity is known for maybe 30 percent.

Some DBPs in chlorine-treated water have been found to raise the risks of various cancers, as well as birth and developmental defects.

Corpus Christi's water supply has high levels of bromide and iodide because of the chemical makeup of the ancient seabed under the water source. Local water sources lead to different DBPs. Whether the types of iodoacids found in Corpus Christi's treated water might be simply a reflection of local conditions, and thus a rare occurrence, is not known.

The DBPs in Corpus Christi's water were found as part of an EPA national occurrence survey of selected public water-treatment plants done in 2002. The survey reported on the presence of 50 high-priority DBPs based on their carcinogenic potential. The report, published in April, also identified 28 new DBPs.

Because so many new DBPs are being found in drinking water, Plewa said, two basic questions should be asked: How many are out there? And how many new ones will be formed as chlorine treatments are replaced with alternative methods?

Co-authors with Plewa on the EPA-funded study were Elizabeth D. Wagner, a scientist in the department of crop sciences at Illinois; Susan D. Richardson and Alfred D. Thruston Jr. of the EPA's National Exposure Research Laboratory; Yin-Tak Woo of the EPA's Risk Assessment Division, Office of Pollution Prevention and Toxics; and A. Bruce McKague of the CanSyn Chemical Corp. of Toronto.

Contact: Jim Barlow, Life Sciences Editor
University of Illinois at Urbana-Champaign

Will boiling water remove chloramine?

Chloramine cannot be removed by boiling water, adding salt, or letting water stand in an open container to dissipate the chloramine.

Other concerns from chloramines in drinking water:

Chloramines, like chlorine, are toxic to fish and amphibians at levels used for drinking water. Unlike chlorine, chloramines do not rapidly dissipate on standing. Neither do they dissipate by boiling. Fish owners must neutralize or remove chloramines from water used in aquariums or ponds. Treatment products are readily available at aquarium supply stores. Chloramines react with certain types of rubber hoses and gaskets, such as those on washing machines and hot water heaters. Black or greasy particles may appear as these materials degrade. Replacement materials are commonly available at hardware and plumber supply stores.

Filtering Out Chloramine

For aesthetic or personal reasons, you may wish to remove chloramine from your water. The National Sanitation Foundation (NSF) has a helpful guide to assist you in choosing a certified drinking water filtration product.

Home Water Treatment Devices

The NSF Water Treatment Device Certification Program requires extensive product testing and unannounced audits of production facilities. The goal of this program is to provide assurance to consumers that the water treatment devices they are purchasing meet the design, material, and performance requirements of national standards.

Selecting and Using Water Treatment Devices

Many consumers have difficulty determining whether they actually need a water treatment system or they are not sure what type of system would be best for them. The choice regarding whether or not to install and use a water treatment system is up to you. If you have identified a specific contaminant whose presence in your water is causing you concern, you can use the drinking water treatment units online product database to try to locate products that have been certified to reduce that specific contaminant.

Consumers are encouraged to educate themselves about the quality of their current drinking water supply. By attempting to identify the contaminants that are present in your water supply, you can then ensure that you are selecting a water treatment system that will be capable of treating those specific contaminants.

It is important to keep in mind that all home water treatment devices need regular maintenance to operate effectively. Please read the operating manual that comes with your water treatment system to ensure you are operating your system in accordance with the manufacturer's directions. Filter cartridges should be changed on a regular basis as recommended by the manufacturer

How much time will it take for both chloramine and chlorine to dissipate and at what ppm level? Can chloramine and/or ammonia be boiled out of water or dissipated by letting the water sit?

While both chlorine and chloramine residuals decrease with time. chloramine takes longer than free chlorine. The chloramine decomposition rate is also affected by the exposure to air and sunlight. Chloramine and ammonia, like chlorine, will eventually dissipate completely over time but it is not practical to let the water sit for these to dissipate. Unlike chlorine, which only takes a few days to dissipate when left to stand, chloramine may stay in water for a few weeks (SFPUC) and ammonia remains in the water even longer. It usually takes days for chloramine to be dissipated when exposed to air and sunlight.

Boiling the water will remove chlorine but it will take much longer to remove chloramine. There are chemicals available that quickly and effectively remove chloramine.

Can charcoal/carbon filters remove ammonia?

Charcoal or granular activated carbon (GAC) treatment can reduce chloramine concentrations of 1 to 2 mg/L to less than 0.1 mg/L. GAC treatment may result in ammonia, chloride, and nitrogen gas as by-products of the adsorption process of chloramine and reaction with the carbon surface. The by-product concentrations will be low (e.g., less than 0.5 mg/L ammonia as nitrogen). However, it may be desirable to remove these by-products depending on water use (CDM, 2003). To remove the low levels of chloramine by-products, GAC treatment should be followed by a reverse osmosis (RO) process. RO should not be used alone as the chloramine residual can damage the RO membrane elements. GAC treatment will remove the chloramine residual allowing RO to effectively remove portions of the other constituents. Owners of home RO units should contact the manufacturer of their units to determine if a GAC unit is installed upstream of the RO system. GAC filters can also remove ammonia but nitrifying bacteria must establish themselves in the GAC column before ammonia removal can occur. Such an application would need to be followed by disinfection step with either a small RO unit or a UV lamp.

Is chloramine a carcinogen?

The EPA has not classified chloramine/monochloramine as to its carcinogenicity because there is inadequate human data and equivocal evidence of carcinogenicity from animal bioassays. (EPA 1992)

Chloramine complications

Alternatives 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 just posted to ES&T’s website (es049971v).

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 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.

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.

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 bacteria, 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 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.

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 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

Over the past few years, Chloramines (a mix of chlorine and ammonia) has been introduced by many public water utilities throughout the country, causing millions of people to be concerned about possible adverse health effects of this "aesthetic" chemical.

It is easy to understand why there is a public outcry about the use of chloramines. When the public water utilities increase chloramine levels, their customers are given precautionary advisories:

1) people with home dialysis machines are warned that their system may not remove chloramines;

2) commercial/industrial water users are advised to review potential operational impacts associated with higher chloramine levels; and

3) people with aquariums and ponds are told that their filters may not be sufficient to remove the chloramines, i.e. their fish may die.

It is interesting that there is all this concern about machinery and fish, but chloramines are supposedly "safe" for the public to drink. It is understandable that people are concerned about drinking water which contains chloramines.

There are many unknowns about chloramines and/or possible chloramine by-products. This shift by public water utilities to a new water disinfectant is driven by the need to balance the use of chlorine to protect against microbes, such as those that cause dysentery and cholera, with the need to keep the dangers of the disinfection process to a minimum.

There are many who ask whether chloramines will result in new, unidentified by-products that may be as or more harmful to human health as the by-products of chlorine.

A Report to the Nation (1988) included a brief discussion of nitrate in the environment as a risk factor for human health. Specifically, the contribution from nitrogen-containing fertilizers to high levels of nitrate in food and drinking water was identified as an environmental health concern. Methemoglobinemia (blue-baby syndrome), various cancers and birth defects were listed as possibly being associated to exposure to elevated nitrate levels in drinking water. The authors of the report suggested a number of control strategies to limit the amount of nitrate entering groundwater supplies. Prevention of groundwater contamination at the source was cited as "the most effective and least costly control strategy available today." 1 However, little progress has been made since that time towards minimizing nitrate inputs into the environment. The increasing contamination of municipal wells and private well water (and surface water supplies) by nitrate, primarily from the widespread use of commercial fertilizers as well as human and animal waste, has been documented in many areas of the U.S. In Iowa, long term use of nitrogen fertilizers in both rural and urban areas has resulted in 30-40% of finished public water supplies with nitrate-nitrogen (NO3-N) concentrations in excess of 5 mg/L, or parts per million ppm.2 The current U.S. Environmental Protection Agency maximum contaminant level (MCL) for public drinking water supplies is 10 ppm nitrate. (Nitrate in this paper refers to NO3-N).

Exposure to nitrate per se is not of particular interest with respect to human health. However, nitrate can be reduced endogenously (within the human body) to nitrite through bacterial and other reactions; nitrite can be further reduced to N-nitroso compounds (NOCs). Infant (< 6 months of age) exposure to nitrite has been linked to development of methemoglobinemia. NOCs are some of the strongest known carcinogens,3 can act systemically,4 and have been found to induce cancer in a variety of organs in more than 40 animal species including higher primates. 5 While some vegetables (lettuce, spinach, celery, greens, etc.), contaminated drinking water, cigarette smoking, and certain medications all contribute to daily nitrate intake in the U.S. population,6 drinking water can account for a substantial portion of that intake.

This paper will present what is known about the human health risks from long-term exposure to low levels (ppm) of nitrate in drinking water. An overview of the extent of nitrate contamination of water supplies will focus on Iowa. A brief discussion of how nitrate works in the human body will set the stage for a detailed description of what is known about health effects from exposure to nitrate in drinking water, focusing on both non-cancer and cancer outcomes. Finally, future needs with respect to research and education will be presented.


  • Hi Stephanie & Peter, Just thought that we'd let you know that we're thrilled to bits with the Twin Under-sink PSI-304 system that you supplied. It arrived yesterday morning, it went in today & the installatiion was an absolute breeze. The fact...

    Tania & John Spencer, .
  • Hi Peter, The filter system arrived on Monday, and installed it today. It was very easy to install and works perfectly. We got use to normal unfiltered tap water so when we tried filtered water the difference was huge. The Sydney water was harsh...

    Luke S, .
  • Peter, "Shame faced husband" ;-) & I were incredibly impressed when the new part & replacement filters arrived today. All installed it looks great & husband proof. Thanks so very much! We are thrilled. You can use this as an unsolicited...

    R Golding, .
  • Hi Peter I have just received and installed my water filter unit. I must say I was dubious at ordering this unit over the web as I felt the pricing had to reflect a lower quality filter system. I am absolutely impressed with both the quality and...

    Barry Englefield, .