Study shows higher risk of childhood leukemia tied to PFAS exposure from household dust

PFAS—a group of chemical compounds made up of per- and polyfluoroalkyl substances— are ubiquitous in the environment. Young children are often exposed to PFAS by ingesting household dust. PFAS are often called “forever chemicals” because they do not easily break down in the environment.

To date, research studies have mostly focused on the risks of adult cancers from PFOS and PFOA, two legacy PFAS which are no longer manufactured in the U.S. but persist in the environment and in human blood. Less has been known about the impact of other legacy and emerging PFAS, especially regarding the risk of childhood cancers.

A study led by Catherine Metayer of UC Berkeley School of Public Health has begun to fill the research gap.

Several years ago, Metayer’s team collected dust samples from 204 households with healthy children, and compared them to dust samples from homes where 178 children developed acute lymphoblastic leukemia, known as ALL. They then analyzed the dust for 33 different PFAS, using targeted liquid chromatography mass spectrometry analysis.

The results, published online ahead of print in the International Journal of Cancer on February 14, 2025, show that children exposed to a mixture of eight PFAS, detected in at least half of the home dust samples, were 1.6 times more likely to develop leukemia than children with lesser exposure—the equivalent of a 60% increased risk. The children were age seven or younger.

“Dust is a reservoir of persistent chemicals, and it’s an interesting snapshot of what a young child is exposed to,” said Metayer, an adjunct professor of epidemiology/biostatistics at UC Berkeley and principal investigator of the California Childhood Leukemia Study (CCLS), conducted by UC Berkeley researchers and supported by supported, in part, by the National Institute of Environmental Health Sciences, the National Cancer Institute, and the US Environmental Protection Agency. CCLS is part of the California Environmental Contaminant Biomonitoring Program, also known as Biomonitoring California, a collaborative effort of the California Department of Public Health and California EPA.

Metayer has been studying childhood leukemia for 20 years, and also directs UC Berkeley’s Center for Integrative Research on Childhood Leukemia and the Environment.

Several years ago, Metayer recalls, she was at a meeting at the National Institute of Environmental Health Sciences (NIEHS), when Linda Birnbaum, who was then the director, had a request.

“Linda Birnbaum came to me at the end of the meeting, and said, ‘Catherine, I need your help. I need you to do a study on PFAS and childhood cancers. People are contacting me…they are really worried.”

After she left the meeting, Metayer thought, “I have to do something.” She remembered the trove of dust samples in her freezer—part of the California Childhood Leukemia Study—and proposed analyzing them for PFAS.

“We measured not only the legacy PFAS but a larger pool—33 different ones—and then focused on the ones that were most commonly detected.”

That the results showed a higher incidence of childhood cancer did not surprise her.

“There are many different ways that chemicals can have a carcinogenic effect,” Metayer said. “The PFAS are affecting a lot of them: oxidative stress, immunotoxicity, and endocrine disruption. For childhood leukemia, alteration of the immune system is a well established pathway that can lead to the development of childhood acute lymphoblastic leukemia. Knowing that PFAS are highly immunotoxicant, that class of chemicals was quite a good candidate to look at in the context of childhood leukemia.”

Within the mixture, individual PFAS had different—sometimes opposite—effects.

For example, N-ethyl perfluorooctane sulfonamido acetic acid (EtFOSAA) contributed the most to the increased risk. Children exposed to the highest level of EtFOSAA were more than twice likely to develop leukemia than those exposed to the lowest studied levels. In contrast, exposure to other PFAS like PFHxS were associated with a reduced risk of leukemia.

Metayer said she does not yet know why, but opposite effects have also been seen in adult cancers.

Her next study will analyze PFAS in blood samples taken when mothers were pregnant, and samples taken from children at birth.