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Scientists are ramping up the research on the potential health effects of a large group of common but little-understood chemicals used in waterproof clothing, stain resistant furniture, nonstick cookware and many other consumer products.
Per- and Polyfluoroalkyl substances are generally referred to by their plural acronym, PFAS. PFAS are resistant to water, oil and heat, and their use has expanded rapidly since they were developed by companies in the mid-20th century. Today, PFAS 'nonstick qualities make them useful in products as diverse as food wrappers, umbrellas, awnings, carpets and firefighting foams. These chemicals are also used in the manufacture of plastic and rubber and in insulation for wiring.
In short, they are all around us.
"We're finding them polluting many rivers, many lakes, many drinking water supplies," says Linda. Birnbaum, director of the National Institute of Environmental Health Sciences and the National Toxicology Program. "
" Essentially everyone has these compounds in our blood, "she explains.
This is partly because PFAS don ' t break down easily – a quality that has earned them the nickname "forever chemicals." Some varieties have been found to stick around in the human body for years, if not decades.
Despite their ubiquity, however, scientists know relatively little about the health effects of most types of PFAS.
No PFAS legal safety limit yet
"Despite their daily use, the body of science necessary to fully understand and regulate these chemicals is not yet as robust as it should be," acknowledged the Assistant Administrator of the Environmental Protection Agency Water Office , David Ross, at a congressional hearing on PFAS in March.
This year, the EPA signaled that it is considering setting a legal safety limit for some PFAS in drinking water, but it has not yet acted.
Meanwhile , public spending on research of the chemicals has gone up. The National Environmental Protection Agency, the National Institutes of Health, the Environmental Protection Agency, the Centers for Disease Control and Prevention and several state university systems have increased their funding for PFAS studies in recent years.
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"We have more and more of our grantees who are looking at PFAS in their studies – both mechanistic studies and animal studies," as well as epidemiological studies that analyze large populations, Birnbaum explains. But the work is slow going.
"These are a very broad class of chemicals – probably 5,000 or more – and it seems like new ones are being produced all the time," she says.
In most cases, U.S. Chemical regulations do not require companies to prove that a chemical is safe before they start selling it. It's up to the EPA to determine whether a substance is unacceptably dangerous and under what circumstances, and typically such analyzes begin only after public health concerns are raised.
As a result, "we really do not know much about the vast majority of these chemicals, "says Birnbaum.
One approach that scientists supported by the National Institutes of Health are taking is to analyze hundreds of PFAS varieties at once. The goal is to identify subgroups of PFAS with similar characteristics, so scientists will not have to do a battery of toxicity tests on each individual chemical.
"There's no way that we'll ever be able to test 5000 or more PFAS , Birnbaum explains.
Early studies suggest some health risks
Some of the most large-scale PFAS epidemiology research in the US. was conducted by a science panel starting in 2005 as part of a class action lawsuit against the chemical company DuPont. The case alleged that thousands of people in West Virginia and Ohio were hurt by industrial releases of a PFAS chemical called PFOA.
The panel was composed of three career epidemiologists who both sides of the court agreed to have an assessment The scientific evidence found a "probable link" between long-term exposure to the chemical and certain medical conditions, such as the kidney cancer and thyroid disease.
Further studies of both humans and gravianes have found similar associations.
"I think we have growing information that at least some members of this class can be problematic," says Birnbaum.
These findings raise a host of new questions, first about mechanism: How do PFAS chemicals act in the body? It's one thing to see an association between exposure to a substance and disease. "We still do not know the exact molecular ways that they produce toxicity," explains Jamie DeWitt, a toxicologist who studies PFAS at East. "It's much more difficult to determine a likely path from chemical exposure to disease symptoms."
For example, DeWitt and others have published studies of both humans and rodents that suggest exposure to one PFAS chemical (PFOA) can suppress the body's response to vaccines.
"I'm pretty sure that a type of the immune cell called B cell is involved in that suppression, says DeWitt. "But I do not know why the B cell does not produce enough antibody. Is it signaling molecules that say," Hey, B cell, make an antibody? " Is it something wrong inside the B cell itself? Is this the amount of energy that the B cell has? These are these molecular mechanisms that we are still trying to figure out. "
Knowing these mechanisms for PFOA could help scientists estimate the potential risks of other PFASs that have a similar structure, she says. "Honestly, I think we're still at the very beginning."
At the current rate of research, Birnbaum says it will take about two years to get a basic handle on the toxicity of the entire PFAS group.
"Realizing that these chemicals have escaped into the environment, how are we going to remedy these problems? How are we going to get rid of these chemicals?" she says.
"A question that we all need to be asking is: What is essential?" she says "Do we really need it? Are there some places where we need this class of chemicals to be safe? But if that's the case, we would like them to be used in closed systems so they do not escape and end up contaminating the whole the world. "
Asked to comment on how essential PFASs are, a spokesperson for the FluoroCouncil, part of the main trade group representing chemical companies in the US, defended their widespread use in consumer products.
" PFAS are an essential enabling technologies that play a vital role in products ranging from lifesaving applications in pacemakers and defibrillators, to the design of lower-emission vehicles with improved auto safety, to the production of semiconductors, solar panels and high-performance electronics, "a spokesperson for the The FluoroCouncil wrote in an emailed statement to the NPR.
"The vast differences within the PFAS family of chemistry are not immediately apparent to many people," the statement goes on. "While some of the names sound the same, PFAS has different characteristics, formulations, intended uses, and environmental and health profiles."
Living with uncertainty
While two years is not very long in the world of basic scientific research, it can feel like an eternity for people who are worried about their health. In the response to public concern, some states are already taking action on their own, both to regulate PFAS emissions and exposure and to collect public health information in communities where the water is known to be contaminated.
"For people who live in areas "There is a really strong demand for information," says Alissa Cordner, a sociologist at Whitman College and one of the nationwide PFAS contamination list organizers.
"There's so much uncertainty about what the scale and the consequences of contamination are," she explains, and that uncertainty makes people afraid. "In terms of individuals wanting to know" What's in my drinking water? " the testing is still prohibitively expensive. "
And even when scientists or officials test water in a community, the lack of scientific evidence so far about PFAS and health makes it hard for people to know how to react. According to the CDC,
"I think it's confusing, because you have so many chemicals, which we know so little, except they are a member of this big class, "says Birnbaum. "I think that's confusing, but it's also frustrating. So we're trying to address these problems right now." Regulators, scientists and citizens all agree: Research results can not come soon enough.