Certain chemicals in the products we use, including fabrics, food packaging, and cooking and cleaning products, can be harmful to human health. The researchers became concerned about a chemical group called per- and polyfluoroalkyl substances, known as PFAS. There are thousands of types of PFAS. They are known as “eternal chemicals” because many break down very slowly in the environment and accumulate in human tissues, such as the liver.
Studies have found detectable levels of PFAS in virtually all American adults. The health effects of PFAS are potentially numerous, as they have been reported to affect fetal growth, organ development, reproduction, and other health outcomes. Studies have shown that they can interfere with hormonal regulation and the immune system.
In recent years, diagnoses of a health condition called non-alcoholic fatty liver disease (NAFLD) have increased for no clear reason. Exposure to certain toxins can increase the risk of NAFLD. A team led by Elizabeth Costello, Sarah Rock and Dr. Lida Chatzi of the University of Southern California Keck School of Medicine investigated whether PFAS affect the liver.
The team collected and reviewed data from 111 research studies involving PFAS and the liver – 25 in humans and 86 in rodents. They reviewed reported data on several PFAS, including three commonly found in humans: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononanoic acid (PFNA). The researchers also looked at levels of liver enzymes in the studies, including alanine aminotransferase, or ALT. ALT is a useful enzyme to study because elevated levels of ALT are a marker of liver damage in humans and rodents.
The study, funded primarily by the NIH’s National Institute of Environmental Health Sciences (NIEHS), was published April 27, 2022 in Environmental Health Perspectives.
The team found that the three common PFAS chemicals were associated with elevated levels of ALT in the blood. This was true in human and rodent studies. In rodent studies, exposure to PFAS was also linked to steatosis, the initial stage of fatty liver disease.
Although human data linking PFAS and effects on the liver is limited, this systematic review of numerous human and animal studies suggests a link between PFAS and NAFLD. Few studies have examined the effects of PFAS on liver injury in men and women separately, but these have suggested that the results differ. This suggests that potential mechanisms for how PFAS might affect the liver may be related to the activity of certain hormones. Further research is needed to uncover the mechanisms by which PFAS might damage the liver, and to what extent.
“This research clearly shows that PFAS should be taken seriously as a human health issue because even after removal, they persist in the environment,” Costello says.
In light of recent findings on the health effects of PFAS, the US Environmental Protection Agency recently announced new measures it is taking to address PFAS pollution.