About a decade ago, researchers at the German Environment Agency noticed a hole in chemical regulation.
There was lots of talk about protecting people from chemicals that build up in the human body. “But what is there that protects water?” Sarah Hale, an environmental chemist from the German Water Center, remembers discussing with colleagues.
Questions like hers sparked a movement to regulate chemicals based partly on their mobility, meaning their ability to move easily with water. Such substances escape most traditional water purification. If they’re also slow to break down, that means they’ll build up in the water supply, where many can cause health problems for humans and ecosystems.
The current poster-children for such chemicals are certain per- and polyfuoroalkyl substances, or PFAS — but other high-profile examples include melamine, which is sometimes used to make wooden dishware and plywood feel smooth, and dapsone, a drug used to treat skin problems. Mobile substances are in many other widely used materials, from household cleaners to construction materials. There’s been a recent surge in regulation aimed at chemicals that build up in the human body, but regulations based on mobility are in their infancy.
This spring, the European Chemicals Agency took a first step toward recognizing the dangers posed by some mobile substances. But the U.S. has yet to follow suit.
For Hale, the European move is a major victory. Some mobile substances are poised to become serious health risks to future generations, but if recent and upcoming regulations limit how widespread these chemicals become in the environment, “it will really change things,” she told Environmental Health News (EHN).
Persistent, mobile and toxic water pollution
To understand chemical mobility, think vinegar and oil. Balsamic vinegar is mobile, so it’s able to mix and move with water, and it’s difficult to remove. Olive oil is not mobile, so it separates from water and it’s easy to skim off the top.
Being mobile does not make a substance hazardous. But when a chemical is also persistent, that’s when problems arise, Hale said. She works with a European collaboration called ZeroPM that aims to limit two groups of mobile compounds in the environment: Those that are persistent, mobile and toxic (PMTs), and those that are very persistent and very mobile (vPvMs) — terms coined by scientist Michael Neumann from the German Environment Agency. Chemicals that take months to lose half their potency warrant regulation, according to a report by Hale and others. But some persistent chemicals can take thousands of years to leave the water supply, she added.
Some persistent and mobile substances are toxic, so the risk of letting them build up is obvious. For chemicals that are very mobile and very persistent, letting them build up is risky even if they’re not known to be toxic because with time scientists may learn that they also pose health hazards.
Take PFAS. For decades, PFAS, some of which are persistent and mobile, built up in water across the U.S. — recently researchers estimated that more than 200 million Americans are exposed to PFAS through their drinking water. Now ubiquitous in our water and lives, researchers have linked exposure to multiple health problems, including cancer and birth defects. If the U.S. had previously regulated chemicals based on mobility, as Hale and others recommend, the PFAS crisis may not have become so bad. Starting regulations now may avoid a similar outcome in the future.
Persistent, mobile and toxic chemicals are a “super heterogeneous, large group of different types of compounds,” environmental technologist Gabriel Sigmund from Wageningen University & Research told EHN. In 2019, scientists assessed more than 15,000 chemicals, and found that 260 qualified as persistent, mobile and toxic or very persistent and very mobile. Around 2,377 chemicals needed more research before scientists could determine whether they fall into these classes.
Unlike certain PFAS that accumulate in the human body, mobile substances rarely build up in humans. Instead, most persistent, mobile and toxic substances are dangerous because people are consistently exposed to low doses through the water they drink, even thousands of miles from where these chemicals are emitted. Compared to other types of pollutants, “it’s much more difficult to confine them, to remediate them, to clean them up,” Sigmund said.
Turning off the tap on toxic mobile substances
Not all persistent, mobile and toxic substances are easy to measure. Commercial water testing labs lack the equipment to test for many of them, and even the most sophisticated labs are blind to some, analytical chemist Mohammad Sadia from the University of Amsterdam told EHN. The true scope of the problem is difficult to assess, Hale said.
Removing the substances from water is another challenge because many aren’t absorbed well by traditional filters. Researchers are developing a new generation of filters that may help solve this problem, Sigmund said. There are two strategies: The first is to develop custom materials that filter out mobile substances well, but are expensive and may be unsustainable to produce. This solution might work best where large quantities of mobile substances are streaming into the water supply, like the outflows of hospitals or industrial plants. The high cost of installing custom filters, and the environmental impact of producing them, could be worthwhile in these hotspots. The second strategy involves finding ways to make traditional types of filters using waste material, so that water treatment plants can use a lot of them. For example, Sigmund was involved in a pilot study in Switzerland in which filters made from waste wood were used.
Ultimately, stopping highly mobile, persistent substances from entering the water supply is the only sure way to prevent harm.
Europe took a step toward this goal in April when persistent, mobile and toxic and very persistent and very mobile substances became two categories in the Classification, Labelling, and Packaging Regulation — a system that describes how manufacturers, transporters and users in the European Union must handle chemicals. The immediate effect will be small —manufacturers will simply need to indicate the presence of such chemicals in products sold in the European Union.
Within a year, however, Hale thinks it’s likely that such chemicals will also become “substances of very high concern” within Europe’s Registration, Evaluation, Authorisation and Restriction of Chemicals framework, or REACH. “That’s when there’ll be more action,” she said. This move could let European regulators limit the degree to which manufacturers can use and emit persistent, mobile and toxic and very persistent and very mobile substances.
Regulations could help stem the flow. But just as importantly, they could deter manufacturers from creating new persistent and mobile chemicals in the future, Sigmund said.
Finally, Hale and her colleagues are working toward entering “persistent, mobile and toxic” as a category into the United Nations Global Harmonized System — an international way of describing the hazards associated with chemicals. This could spread awareness to parts of the world outside of Europe, Hale said.
Regulating mobile chemicals in U.S. water
Although the movement has centered in Europe, some people in the U.S. have been talking about the concept of mobility for decades, environmental scientist Erika Schreder, from the environmental health research and advocacy group Toxic Free Future, told EHN. For example, Toxic Free Future advocated for the city of Seattle to stop using certain pesticides in the late 1990s and early 2000s, partly because these chemicals are mobile.
Schreder isn’t aware of regulations in the U.S. that are based on chemical mobility. However, the Washington State Department of Health and Department of Ecology are planning to reconsider the rule for describing chemicals that are persistent, bioaccumulative and toxic starting early next year. Although most mobile compounds don’t bioaccumulate in a classical sense, people are constantly exposed through drinking water, which has a similar effect. Because of this, “it’s possible that we could put the mobility into the new rule,” Holly Davies, a toxicologist at the Washington State Department of Health, told EHN. In the next five to 10 years, this could lead to some of these chemicals being restricted in Washington state.
When EHN asked the Environmental Protection Agency if they would like to comment, a representative from the press office asked if the reporter was referring to persistent, bioaccumulative, toxic substances. When the reporter explained that PMTs are a related but separate class of chemicals, the EPA did not offer further comment.
Schreder hopes to see wide-spread action soon. If persistent, mobile compounds are allowed to build up in drinking water, “we could end up very sorry,” she said.