Health fads come and go, but drinking more water (and less beer and soda) is one of the few things that's unequivocally good for the human body. It should be as easy as putting a glass under the tap, but what kinds of potentially harmful chemicals lurk there? News that 3M is paying more than US$10 billion (351 billion baht) to clean "forever chemicals" from municipal drinking water isn't helping our confidence.
Susan Richardson, a former EPA chemist now at the University of South Carolina, has been working to establish a big-picture view -- using an instrument that can measure the relative abundance of different kinds of chemical contaminants. She's been following the forever chemicals (polyfluoroalkyl substances, or PFAS) for 30 years, but she's come to realise that for most of us, these likely pose a minor threat compared to something else -- the chemicals that form spontaneously as a byproduct of water disinfection.
In most areas, the concentration of these disinfection byproducts is 1,000 times greater than the forever chemicals. And the toxicity of the DBPs is worse.
Ms Richardson says she thinks disinfection byproducts are getting less attention from the public and from the EPA because "forever chemicals" is such an attention-grabbing name. She suggested we call DBPs "everyday chemicals", but that label doesn't quite have the same ominous sound. Maybe "Frankenstein chemicals" would grab more attention -- and underline that these compounds are made up of a scary hodgepodge of different pieces.
She worries that new EPA regulations on PFAS could be focusing limited resources on PFAS when other contaminants are being ignored.
Risk communication consultant Peter Sandman has said that people's experience of risk is the sum of hazard (the probability of being killed or harmed) and an outrage factor. Forever chemicals created by a huge company can raise outrage -- but it's hard to get people enraged about compounds that aren't made by any particular company but form spontaneously following a process that's considered a triumph.
Many of us have gotten used to that chlorine smell from our taps. But we don't have to accept chemicals in our water to ensure it's free of disease-causing parasites, bacteria and algae. There are many ways to disinfect water -- chlorinating, ozonating, chlorine dioxide, UV -- and some are more prone to creating dangerous byproducts.
Filtration using activated carbon can catch disinfection byproducts and forever chemicals, but it's expensive and should be deployed where it's needed most. People can pay for filters at home, but that's unfair to the many people who can't afford them.
Providing clean water will become more challenging with a changing climate and increasingly prolonged droughts. In El Paso, Texas, the municipal water plant is gearing up to reuse wastewater -- something that might become more necessary there and elsewhere. In California, too, there are systems where wastewater is injected underground and then disinfected for "indirect" reuse.
It's been hard, until recently, to get a big-picture comparison of different kinds of chemical contaminants because there are hundreds of compounds that fall into the category of DBPs and PFAS.
The specific disinfection byproducts in your community depend not just on how municipal water is disinfected but on how much natural organic matter and salt is in the source water. Salts can come from proximity to the ocean or even to an ancient ocean whose residual salts leach into the groundwater. Fracking often dislodges natural iodide salt, which tends to form the most toxic disinfection byproducts.
So what ends up in your water includes a complicated brew of compounds formed in reactions between natural organic matter, salts, industrial waste and other pollutants, and the chemicals added for disinfection.
Right now, there are about 700 compounds known to be formed from disinfection, but only 11 are regulated. And those aren't the most dangerous, said Ms Richardson.
There are implications here for PFAS, too. Some studies have suggested there are thousands of PFAS, but Richardson says there aren't thousands of industrial PFAS products. Some could be fragmenting or combining with other chemicals, forming new unnatural, long-lived compounds.
Ms Richardson's been sorting this out with a rare instrument that does combustion ion chromatography. With it, she can take a drinking water sample and measure the total concentration of all the organic compounds containing fluorine -- which corresponds roughly to the total of all the PFAS contaminants because there are few other sources of fluorinated organic compounds in water. (Note that although it sounds similar, fluoride -- added to water for dental health -- is a different chemical and irrelevant here.)
Both PFAS and DBPs are considered halogenated organic chemicals because they include atoms of the halogens -- fluorine, chlorine, bromine and iodine. The DBPs are the primary source of any such compounds with chlorine, bromine and iodine, and the instrument can measure the full burden of those as well.
It also matters which of these compounds actually causes harm to the human body. Toxicology studies using animals or other model systems have shown that both PFAS and DBPs can potentially cause cancer and other health problems. But it takes epidemiology to connect exposures in the real world to clusters of cancer or other diseases. There is compelling epidemiology tying PFAS to high cholesterol and some evidence for decreased male fertility. For DBPs, epidemiological studies have revealed connections to bladder and colon cancer.
These studies can't connect any individual cancer case to chemical pollution -- but they suggest some fraction of people with cancer would not have gotten sick if not for DBPs in water. That's unacceptable. We should all be able to drink from the tap and know we're improving our health -- not putting it in jeopardy. ©2023 Bloomberg
FD Flam is a Bloomberg Opinion columnist covering science. She is host of the 'Follow the Science' podcast.
