These ‘forever chemicals’ could be contributing to rising rates of nonalcoholic fatty liver disease
By Kevin Loria
You might have never heard of nonalcoholic fatty liver disease, but it is now a global epidemic, thought to affect roughly 25 percent of the world’s population—including approximately 89 million Americans. It’s a matter of grave concern because untreated, the condition can progress to serious liver injury, including cirrhosis and liver failure.
Now a new research review suggests that one contributing factor to rising rates could be PFAS, the ubiquitous chemicals used in nonstick pans, waterproof gear, firefighting foam, takeout containers, and more.
Researchers have identified several conditions that put people at greater risk for nonalcoholic fatty liver disease (NAFLD), including obesity, high blood pressure, and high cholesterol. And previous research suggested that exposure to environmental chemicals such as PCBs—banned since the 1970s but still found in the environment—could also play a role. In the new review, published Wednesday in the journal Environmental Health Perspectives, researchers looked at both human and animal studies and found that exposure to PFAS may be a significant risk factor as well. While researchers have identified several conditions that put people at greater risk for NAFLD, including obesity, high blood pressure, and high cholesterol, the driving forces behind the significant rise in cases that have made this condition so common are less well understood.
PFAS and Your Health
PFAS have long been used in a wide variety of products and are often called “forever chemicals” because they don’t break down naturally or they do so extremely slowly. That means they accumulate in the environment and in us. In recent decades, PFAS have been linked to a growing list of health problems, including a weakened immune system, kidney damage, and increased risk for certain cancers.
There has at times been a perception that the effects of PFAS exposure on the liver are somewhat uncertain, says Alan Ducatman, MD, professor emeritus at West Virginia University’s School of Public Health, who co-wrote a commentary on the new review. But “it’s not the case that the findings of PFAS are inconclusive or inconsistent, they are quite consistent,” he says—as this new review confirms. Scientists should feel confident calling PFAS “hepatotoxic,” or damaging to the liver, Ducatman says.
Liver damage has long been observed in communities exposed to high levels of PFAS, says Jamie DeWitt, PhD, a professor of pharmacology and toxicology at East Carolina University, who was not involved with the new study. The new review helps solidify these observations. “Evidence from epidemiological studies and animal studies confirms the liver is targeted by PFAS,” she says.
What the Study Found
To better understand how PFAS exposure is linked to liver damage, the authors of the new review examined evidence from 25 studies in humans and 86 studies in rodents.
“We’ve seen for years, in isolated studies, that PFAS might have toxic effects in the liver,” says Elizabeth Costello, a PhD student in the department of population and public health sciences at the Keck School of Medicine and one of the lead authors of the study. “Researchers have seen this before in occupational health studies and in population health surveys, but this review lets us put it all in one place. This review can show that the evidence points in the same direction, even if some individual studies find no relationship.”
In people, the evidence clearly shows that exposure to certain PFAS is connected to higher levels of a liver enzyme that’s used as an indicator of liver damage, and that is also elevated in people with NAFLD. That same link is found in animal studies, which also show that rodents exposed to PFAS have abnormal fat accumulation in the liver.
To confirm that PFAS directly causes NAFLD in people, scientists will still need to do more research that follows subjects for multiple years, Costello says. But the evidence so far strongly suggests that’s the case, Ducatman says. It’s possible, he says, that PFAS exposure increases people’s susceptibility to NAFLD. That increased susceptibility combined with other risk factors, including high-calorie diets and sedentary lifestyles, could help explain the rise in the condition.
This new review helps clarify exactly how PFAS might affect the liver, which will help researchers figure out what to look for in future studies, DeWitt says.
And while more research is needed to identify exactly how much PFAS exposure may lead to liver damage, some concerning changes are seen even at very low levels of exposure, Ducatman says. This could be a reason for public health authorities to consider monitoring liver health in communities known to be highly exposed to PFAS.
Another question that needs to be answered is whether or not all PFAS cause these same effects. Most of the studies on people focus on just a few of the best-known PFAS chemicals. Several of these have already been largely phased out of production in the US, though they are still commonly found in people because they persist in the environment. And there are thousands of other potential PFAS out there, with hundreds in use, which are far less studied. But even if we don’t know for sure that all PFAS cause the same effects, chemicals that serve a similar purpose may have similar effects on the body, Ducatman says.
Right now, because only a few of these chemicals have been phased out, it may leave many people exposed to the potential health effects caused by replacement chemicals. “If we’re going to be using PFAS, we’re obligated to figure out which if any are safe, rather than assuming they’re safe unless proven otherwise,” Ducatman says.
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