Many public water systems in the United States presently use inorganic chloramines to disinfect drinking water, however, researchers thus far had not identified what decomposition products (DP) existed in the tap water.
In a new study published in SCIENCE journal on 22 November 2024, by researchers from University of Arkansas, Institute for Biogeochemistry and Pollutant Dynamics, at ETH, Zurich and US Environmental Protection Agency, reports the discovery of what the researchers called chloronitramide anion – a decomposition product – a compound whose existence, though not identity, has been known for 30 years. They have already detected it in the tap water. Since the toxicity of chloronitramide anion (Cl–N–NO) remains untested, researchers called for its immediate toxicological evaluation.
According to the researchersm this toxic material is present in the drinking water of over 113 million of US population. A quick search shows that inorganic chloramines are used in the United Kingdom, Australia, Finland, and Spain.
Chemical disinfection indispensable
Chemical disinfection kills pathogens in public water supplies effectively reducing waterborne diseases in drinking water and have been used for over a century. Inorganic chloramines such as monochloramine (NH22Cl) and dichloramine (NHCl2), have become widely used in the U.S. for this purpose and are used to treat the tap water of nearly one-third of all Americans.
However, for decades, researchers knew that chloramine decomposition products were released during disinfection. These chemical products were elusive; they included potential nitrogen-containing compounds with unknown toxicity. One such disinfection by-product, referred to simply as an “unidentified product”, remains uncharacterized despite being first identified more than 40 years ago.
Mysterious chemical identified
Julian Fairey, Associate Professor in the Department of Civil Engineering at the University of Arkansas and other researchers combined classic synthesis methods with advanced analytical techniques such as high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy and isolated and identified chloronitramide anion (Cl–N–NO2–) as a previously unidentified product of inorganic chloramine decomposition. They measured chloronitramide anion content in a range of chloraminated water systems in the U.S., detecting levels as high as ~100 micrograms per liter (μg/l), which surpasses the typical regulatory limits for many disinfection by-products (60–80 μg/liter).
Researchers found that this compound was absent in water systems that used alternative disinfectants. Although they have not yet carried out direct toxicological studies, they caution that computational analyses suggest that chloronitramide anion may not be benign thereby emphasizing the need for an immediate toxicological assessment and quantification in source waters, finished drinking waters, and wastewater effluents.
Chloronitramide anion present in all samples
“Analysis of chloraminated United States drinking waters indicated Cl–N–NO2− occurrence in all samples tested (n = 40), with a median concentration of 23 μg L−1 and first and third quartiles of 1.3 and 92 μg•L−1, respectively. Researchers concluded that Cl–N–NO2− warrants urgent occurrence and toxicity studies in chloraminated water systems that serve >113 million people in the United States alone.”
Some general remarks
For more than 100 years, drinking water disinfection, primarily with chlorine, has been used to inactivate pathogens to curb waterborne disease and safeguard public health. It is very efficient as a disinfectant; however, chlorine reacts with natural and anthropogenic organic matter, bromide, and iodide to form disinfection by-products that have been associated with many adverse health effects such as bladder and colon cancer, low birth weight, and miscarriage.
Of the estimated 600 to 700 disinfection by-products identified over the past 50 years, trihalomethanes and halo acetic acids are the predominant compounds formed on a mass basis during chlorine disinfection, and they are regulated in the US by the Environmental Protection Agency (EPA). Since promulgation of the 1998 EPA Stage 1 Disinfectants and Disinfection Byproducts Rule, many public water systems have switched to alternative disinfectants, including inorganic chloramines. Recent surveys of US drinking water systems estimate that >113 million people are supplied chloraminated drinking water. Although inorganic chloramines form fewer regulated disinfection by-products, they may enhance the formation of other disinfection by-products, including those containing nitrogen, which may be more toxicologically relevant.
Zoom Webinar
A related embargoed news briefing was held on Tuesday, 19 November, as a Zoom Webinar. It indicated the interesting nuances in the discovery and characterization of the mysterious byproduct.
Meagan Phelan, on behalf of Triple as the Nonprofit International Science Society that publishes the science family of journals welcomed the reporters and the researchers. She moderated the Webinar competently. Her timely interventions and relevant questions improved clarity particularly when the researchers ‘responses appeared to be inadequate or vague.
Media reactions
“While the toxicity of chloronitramide anion is still unknown, the researchers expressed alarm about both its prevalence and its similarities to other problematic substances.” — The Hill (21 November 2024)
“Epidemiological studies showed that some people who drink chlorinated water over a long period of time have a higher risk of colon and bladder cancers. For pregnant people who drink chlorinated water there was also a potential association with miscarriages and people who gave birth to babies with low birth weights.” — CNN
“The fact that a byproduct with unknown risks could be so ubiquitous and evade researchers for so long renews questions about potential health effects of the chemicals used to treat tap water. — NBC News (21 November 20240”
“The water is still safe to drink. Tap water is more regulated, with more people working on it, than bottled water,” said Lisa Ragain, a principal water resources planner at the Metropolitan Washington Council of Governments who serves on the National Drinking Water Advisory Council’s Microbial and Disinfection Byproducts Rule Revisions Working Group.” — Washington Post 21 November 2024)
Many news outlets prominently published this news story, and social media buffs claimed the “news became viral” following the researchers addressing the webinar.
The Researchers
- Julian Fairey, Associate professor in the Department of Civil Engineering at the University of Arkansas.
- Julie Lasakovitz, Postdoctoral Researcher Institute of Biogeochemistry and Pollutant Dynamics the Department of Environmental systems, Science at Eth Zurich.
- Christopher Mcneil, Professor in the department of Environmental System, Science and head of the Institute for Biogeochemistry and Pollutant Dynamics, alsho at ETHZurich.
- David Wahman, Research Environmental Engineer at the United States Environmental Protection Agency Office of Research and Development, the Center for Environmental Solutions and emergency response.
Each one of them highlighted his/her role in the eminently laudable multidisciplinary research programme.
How the project started
Responses to a series of questions such as “What motivated you to focus on this mystery? And was it easy to free up the resources. For this also, in your opinion, has enough priority and resources been given to identifying this up over the past decades? from Netherlands briefly and elegantly revealed how the program started.
Julian-Wahman collaboration
Julian Fairey revealed that he and David Wahman went to graduate school together at the University of Texas and both had worked on problems related to chloramine chemistry since then. In Wahman’s early years at the EPA as a postdoc, he also worked on some chloramine projects.
Fairey arrived at the University of Arkansas about 15 years ago. He recalled that they have been working on problems related to this for the last 10 to 15 years.
There are a host of different disinfection byproducts referred to as nitrosamines that form in chloramine systems, and the two researchers Fairey and Wahman, weren’t really satisfied with their own explanation for how those compounds were formed. They thought it was related to the Chloramine Chemistry, and so Fairey got a grant from the National Science Foundation back in 2020 to study the formation of nitrosamines in chloramine systems, and really look at the chloramine chemistry and that led to a couple papers in environmental science and technology, one in 2021, one in 2020,
Co-authors Fairey and Wahman found these sort of intermediate products that form in in chloramine systems that are basically key in forming nitrammite anion. Thus, they got into this in a little bit of a different way. It took Fairey a while to secure funding particularly for this, so he said that he is very thankful to the National Science Foundation.
As Dave Wahman and Julian Fairey work as engineers, there was only so far they were going to get on this study. Fairey’s sabbatical came at that time; he recalls that he was very fortunate to land in Chris Mcneil’s lab, and he was able to bring a lot of his expertise to bear in in terms of trying to understand what this compound might be. Julie Lasakovitz worked, on the analytical side of things, and so this ended up being a nice collaboration in that respect.
But while Dave and Julian are more engineers, Chris and Julie are more of scientific mold. And they really needed that pairing to solve this problem. Fairey emphasized how robust and sound their collaboration was.
At this point, Meagan Phelan, the moderator asked them how often are they all interfacing with the people working at water treatment facilities, and like talking with them or getting feedback from them? What does that look like in their workflows?
David Wahman: “Personally, every now and then, mainly at conferences. We’ll try to interact there and then we do have. Environmental Protection Agency (EPA) has a technical assistance program that I’ve been on a few times to talk with operators, and I’ve done training on chlorine chemistry for operators and stuff like that. But I wouldn’t say that it’s frequent, but it does happen.”
Question from Lauren, from Popular Science: Given that there are well understood toxins related to chlorine breakdown. What might safer alternatives to chloramine be for water treatment? If this byproduct also proves toxic?
Julian Fairey recalled that this was discussed a little bit in the in the perspective article by Daniel McCurry. Fairey explained that in the US, we need a residual in our distribution systems to keep water safe. We don’t want to get people sick, and chloramines provide safe drinking water.
“But you know, if this, if this compound eventually does prove to be toxologically relevant at the levels it forms in drinking water. (And again. We’re not there):
“There are alternatives, I mean, Dave talked about kind of home use alternatives. You’ve read about sorts of things that might be successful at removing this compound, but at a larger scale. you know, utilities could consider switching back to free chlorine, which is, you know, often what they’ve switched from free chlorine would need to be coupled with enhanced removal of the organic precursors of disinfection byproducts that are regulated and so that could be a more expensive proposition to quote.”chlor-chloramination”. Sorry? But I don’t think we’re there yet, but in terms of home use these Brita filters, they might be successful. But certainly, if a disinfectant switch needs to happen, it probably need to be coupled with enhanced removal of the organic precursors of regulated disinfection, byproducts,” he clarified.
As an independent observer, I believe the researchers presented their notable work very nicely. However, when the media asked practical and socially relevant questions there was some confusion. They did not answer convincingly the ways and means by which harmful products can be removed at home It appears that none of the researchers expected such questions. Could it be that they did not want to enter any seemingly unfamiliar territory? In that context, all news outlets by and large did a better and reassuring job. It appears that the researchers did not realize that they must respond to relevant practical questions convincingly without sacrificing objectivity and scientific accuracy.