Researchers from Keck Medicine of USC have identified another potential cause of liver damage. A new study published in Liver International links tetrachloroethylene (PCE), a chemical widely used in dry cleaning and found in household products like adhesive glues, spot removers, and stainless steel polish, to serious liver harm.

According to the findings, exposure to PCE can triple the risk of significant liver fibrosis, a condition where scar tissue builds up in the liver. Over time, this scarring can progress to liver cancer, liver failure, or even death. The study also revealed a clear dose-response relationship: the greater the exposure to PCE, the higher the likelihood of developing liver fibrosis.

"This study, the first to examine the association between PCE levels in humans and significant liver fibrosis, underscores the underreported role environmental factors may play in liver health," said Brian P. Lee, MD, MAS, a hepatologist and liver transplant specialist with Keck Medicine and lead author of the study. "The findings suggest that exposure to PCE may be the reason why one person develops liver disease while someone with the exact same health and demographic profile does not."

Everyday Exposure to PCE

PCE is a man-made, colorless liquid widely used to remove grease in industrial and household settings, including dry cleaning. People are often exposed to the chemical through the air when it slowly evaporates from recently dry-cleaned clothes. It can also enter drinking water when spills or improper disposal contaminate soil and groundwater.

The International Agency for Research on Cancer classifies PCE as a probable carcinogen. Previous studies have connected it to bladder cancer, multiple myeloma, and non-Hodgkin lymphoma. Dr. Lee noted that other research has also linked PCE exposure to liver cancer.

Because of these health concerns, the U.S. Environmental Protection Agency has initiated a 10-year phaseout of PCE in dry cleaning and placed restrictions on its use in other industries. Still, the chemical persists in certain products and remains unregulated in some countries.

Study Findings: Greater Exposure, Greater Risk

Lee and his colleagues analyzed data from the National Health and Nutrition Examination Survey (NHANES), a large, nationally representative study of U.S. adults. They examined blood samples from participants aged 20 and older collected between 2017 and 2020 and found that about 7% of people had detectable levels of PCE.

Those with measurable PCE exposure were three times more likely to have significant liver fibrosis compared to those without exposure, regardless of age, sex, race, or education level.

Interestingly, higher-income individuals appeared more likely to have detectable PCE in their blood, possibly due to greater use of dry-cleaning services. However, workers in dry-cleaning facilities may face the highest risk because of long-term, direct contact with the chemical.

For every one nanogram per milliliter increase in PCE in the bloodstream (a nanogram equals one-billionth of a gram), the likelihood of significant liver fibrosis rose fivefold.

A Hidden Explanation for Unexplained Liver Disease

The researchers found that traditional risk factors like alcohol consumption and fat accumulation in the liver did not appear to influence fibrosis when PCE was present. "Patients will ask, how can I have liver disease if I don't drink and I don't have any of the health conditions typically associated with liver disease, and the answer may be PCE exposure," said Lee.

Dr. Lee emphasized that PCE may be just one of several environmental toxins contributing to liver disease. "No doubt there are other toxins in our environment besides PCE that are dangerous to the liver," he said.

He also hopes the findings will lead to earlier detection and better outcomes for those affected. "We hope our research will help both the public and physicians understand the connection between PCE exposure and significant liver fibrosis," Lee said. "If more people with PCE exposure are screened for liver fibrosis, the disease can be caught earlier and patients may have a better chance of recovering their liver function," said Lee.

• Large real-world study finds new GLP-1 drugs help protect the heart in people with cardiovascular risk.
• Clear evidence shows these medications support heart health beyond their weight-loss effects.
• Semaglutide (Ozempic) and tirzepatide (Mounjaro) offer similar levels of heart protection, with only small differences in results.

GLP-1 Drugs Linked to Better Heart Health

Injectable medications used for weight loss may also lower the risk of major cardiovascular problems in people with type 2 diabetes. Researchers from the Technical University of Munich (TUM) and Harvard Medical School reached this conclusion after analyzing insurance claims data. Their findings show that semaglutide and tirzepatide (sold as Ozempic and Mounjaro) can reduce the risk of serious heart-related events by as much as 18 percent.

The research, published in Nature Medicine, drew on a vast collection of data from U.S. health insurance records. "Those data are collected in routine clinical care and can be used for research. They allow us to answer a broad range of relevant questions efficiently. Importantly, we are studying patients who reflect everyday clinical practice -- unlike the highly selected participants typically enrolled in randomized trials," explains Dr. Nils Krüger, the study's lead author and a physician at the Department of Cardiovascular Diseases at the TUM University Hospital German Heart Center.

Heart Protection Beyond Weight Loss

The results clearly indicate that these newer diabetes treatments help protect the heart in people with elevated cardiovascular risk. Compared with sitagliptin, a diabetes medication known to provide no measurable heart benefits, semaglutide cut the risk of stroke and heart attack by 18 percent. Tirzepatide lowered the combined risk of stroke, heart attack, and death by 13 percent compared with dulaglutide, an older GLP-1 drug already in use.

"Both substances have a cardioprotective effect. Our data show that the benefits emerge from early on, indicating that the effect goes beyond weight loss alone," says Dr. Krüger. However, researchers note that the biological mechanisms behind this protective effect remain uncertain.

Because semaglutide and tirzepatide are relatively new, studies directly examining their cardiovascular effects have been limited, especially those comparing the two drugs head-to-head. The research team from TUM, Harvard Medical School, and Brigham and Women's Hospital aimed to fill this knowledge gap to guide better treatment decisions for patients at risk of heart disease.

Comparing Ozempic and Mounjaro

"According to the manufacturers' claims, each one suggests its own product is more effective than the competitor's at reducing cardiovascular risk," says Prof. Heribert Schunkert, Director of the Department of Cardiovascular Diseases at TUM University Hospital. "Our study, however, shows only small differences in heart outcomes between tirzepatide and semaglutide in the risk groups we analyzed."

Dr. Krüger adds: "We hope our findings will provide clarity to physicians about how these new medications perform in clinical practice. Our transparent study design is also intended to support open scientific discussion about whether and how modern GLP-1 drugs should become part of the standard therapeutic repertoire in cardiovascular medicine."

Recently, Dr. Krüger's team was able to show that treatment with semaglutide or tirzepatide can reduce health risks for people with heart failure with preserved ejection fraction by over 40 percent. The study has been published in the journal JAMA (PMID: 40886075).

This work was funded by the National Institutes of Health (R01-HL141505, R01-AR080194) and the German Heart Foundation (S/02/24, SRF-HF/24, RWE/11/25).