Mysterious Chemical By-Product in U.S. Tap Water Finally Identified

A mysterious by-product of a chemical used to disinfect the tap water of about one-third of Americans has finally been identified, and the international research team behind the discovery is advocating rapid assessment of its potential toxicity.

The research, reported Thursday in the journal Science, does not claim that tap water containing the by-product is unsafe to drink or that the finding represents any kind of emergency. All water, including bottled water, contains contaminants.

But the discovery of a new and previously unknown chemical, called chloronitramide anion, could have implications for municipal water systems that use a class of chlorine-based disinfectants called chloramines. For decades these disinfectants, derived from the mixture of chlorine and ammonia, have been added to many municipal water supplies to kill bacteria and prevent waterborne illnesses.

“We need to investigate it. We don’t know the toxicity,” said environmental engineer Julian Fairey, an associate professor at the University of Arkansas and lead author of the paper. “This work was 40 years in the making in terms of trying to identify the compound, and now that we have identified it, we can delve into how toxic is this thing.”

Initial computational modeling of the compound shows similarities to other chemicals with demonstrated toxicity, which “suggests that it is probably not harmless,” Fairey said.

Water-quality experts not involved in the new study said such modeling is an initial method of trying to understand a chemical’s toxic potential, and urged people not to be alarmed.

“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.

Scientists and policymakers have long known that disinfecting water requires a balance of risks and benefits. Clean drinking water is a public health triumph, making a major contribution to increasing life expectancy over the past century across much of the planet. Before the implementation of filtration and chlorination of water in U.S. cities in the early 1900s, waterborne illnesses such as typhoid fever and cholera were common.

But those benefits have to be weighed against the risk of chemical by-products created when a disinfectant reacts with organics in the water, or decomposes.

Scientists realized in the 1970s that chlorine added to the water supply not only killed germs but reacted with organic compounds – such as those produced by decaying plant material – to create “disinfection by-products.” Some of those contaminants have been linked to cancers and miscarriages, and are now regulated by the Environmental Protection Agency, which limits their concentration in the water supply.

Chloramination provided an alternative way to disinfect water. But it created by-products of its own, and one compound has for decades remained mysterious – its formula and structure eluding characterization. Researchers had no name for it, and just called it “unidentified product.”

That product turns out to be chloronitramide anion, a compound of chlorine, nitrogen and oxygen atoms.

This is a novel chemical. It doesn’t appear in the Chemical Abstracts Service, a registry of 219 million substances. “It’s like the number of stars we have in the sky for chemistry,” said Beate Escher, a toxicologist at the Helmholtz Center for Environmental Research in Leipzig, Germany, who was not involved in the study.

The word “chemical” is a generic term for all manner of natural and synthetic compounds that are ubiquitous in our lives. The big question now is whether chloronitramide anion is a meaningful threat to human health at the kind of concentrations seen in tap water. Escher and other experts noted that these questions need to be answered, but shouldn’t scare people so much that they avoid their faucets.

“Do not panic,” Escher said. “I wouldn’t be worried too much. It would be nice to test it toxicologically.”

The EPA issued a statement responding to the new report.

“Further investigation of this previously unidentified product of chloramine decomposition will be needed before EPA can determine if regulatory action is warranted,” Dominique Joseph, an EPA spokeswoman, said in an email.

The mystery by-product was first noticed in the 1980s and became the subject of EPA-funded research, but scientists were unable to isolate it and determine its molecular formula or structure.

Using more-advanced technologies, Fairey and colleagues at the EPA and a Swiss research center solved the mystery. They separated the compound from other anions in the water using an ion chromatograph, and used an ultra-high-resolution mass spectrometer to obtain its molecular formula: one chlorine atom, two nitrogen atoms and two oxygen atoms, plus a negative charge.

They still needed more data to get their paper through peer review and published in a journal: They needed the structure of the molecule – the way the atoms bonded – and discovered it this year, using a technique called nuclear magnetic resonance spectroscopy.

The next step was to see if the newly identified compound was present in samples of chloraminated drinking water. They found it present in all the archived samples of drinking water in Fairey’s lab. The researchers performed a limited survey of chloramine-treated water from 10 systems in seven states. The chemical was again found in all samples studied, ranging from 1 microgram to 120 micrograms per liter. That’s a strikingly wide range, and the higher concentrations exceed those of two regulated groups of disinfectant by-products in drinking water with limits of 60 and 80 micrograms per liter, Fairey said.

The process to regulate this by-product could take years to implement, and would need to start with toxicology studies that better characterize whether it is harmful. Chemists will need to isolate a pure version of the chemical in sufficient quantities to test how it interacts with living cells and animals.

In the meantime, water system officials could switch their disinfection practices, reverting to chlorine. But water systems that switched to chloramine often did so because they needed to reduce the concentration of problematic by-products created when chlorine reacted with organic material. That means switching back to chlorine would probably require expensive efforts to remove those organics from the water.

Other methods of disinfecting water include ozone and ultraviolet light, but these are short-lived methods, and to prevent the possibility of reinfection of the water between treatment plant and tap, legally they must be followed by a second, longer-lasting disinfectant, such as chlorine or chloramines.

“It’s a pretty important finding. It’s like 10 percent of the disinfectant is disappearing and becoming this mystery product that we all developed collective amnesia about,” said Daniel McCurry, a professor of civil and environmental engineering at the University of Southern California who was not involved in the work.

McCurry said the chemical structure of the compound has some “exotic features” that make him suspicious that it could be toxic. He also noted that chloramine disinfection can have some other negatives, such as increasing the release of lead from pipes. In D.C., a switch to chloramine disinfection in 2001 temporarily increased lead levels in drinking water, until another chemical was added.

In a “Perspective” article in Science accompanying the new research, McCurry wrote, “Regardless of whether chloronitramide anion is found to be toxic or not, its discovery warrants a moment of reflection for water researchers and engineers.”

Waterborne illnesses remain rare in developed nations thanks to disinfection of source water, and the new research does not call into question the need for such efforts. Without disinfecting the water supply, “we’d bring back the days of cholera. People would be dying of waterborne illness on a day-to-day basis. Disinfecting drinking water is one of the 20th century’s greatest public health achievements,” Fairey said.

The new report comes amid a flurry of attention to the public drinking-water supply, triggered by President-elect Donald Trump’s plan to nominate Robert F. Kennedy Jr. to be secretary of the Department of Health and Human Services. Kennedy has vowed to remove fluoride from drinking water despite its strong support from the public health community, which for decades has championed fluoridation as a successful tool to fight tooth decay.

The new finding is completely unrelated to that debate. Fairey said almost anything can be hazardous to health depending on the dose. In his view, the fluoridation of public drinking water promotes dental health and is not dangerous.

Research conducted in the 1990s suggests that carbon-based water filters would probably remove the newly identified chemical, Fairey said, but that needs to be tested, along with whether filtration itself creates new by-products.

(c) Washington Post