Exposure to “permanent chemicals” during pregnancy may increase the risk of childhood asthma, according to a new study from Sweden.
Researchers at Lund University have found that prenatal exposure to extremely high levels of per- and polyfluoroalkyl substances known as PFAS in drinking water is consistent with high rates of childhood asthma in communities that have dealt with decades of pollution.
The findings, published Thursday in the journal PLOS Medicine, are noteworthy. Exposure to PFAS causes a myriad of well-documented health effects, but its association with asthma has not been well studied.
“We were surprised because we had no expectations going into the study,” said study co-author Anneliese Blomberg, an associate researcher in epidemiology at Lund University.
The researchers stressed that the association they found was limited to very high levels of PFAS exposure and said the study needs to be replicated. Still, it affects people around the world who are permanently exposed to high levels of chemicals.
“This is a public health impact that has gone completely undetected until now,” Blomberg said.
This study adds to a long list of proven human health harms from PFAS exposure and a growing list of causes of environmental asthma. Researchers have called childhood asthma a “global epidemic,” and its incidence has been rising in recent decades. As threats to lung health are further exacerbated by rising air pollution, exposure to toxic substances, and heat amplified by climate change, now is a critical time to understand the causes of respiratory diseases.
PFAS (forever chemicals) have been widely used in many consumer products since the 1940s. They are now ubiquitous, found in drinking water, fish, livestock, and more. The new study focused specifically on aqueous film-forming foam (AFFF), a fire extinguishing agent that contains several harmful PFAS.
Residents of the southern Swedish city of Ronneby were unknowingly exposed to water containing high levels of PFAS for more than 30 years after AFFF runoff from the local military airfield contaminated one of the two municipal water supplies. About a third of the city’s residents had been drinking highly contaminated water for years before the contamination was discovered in 2013 and the water system was shut down. Subsequent tests revealed extremely elevated levels of PFAS in their blood.
Researchers followed a cohort of more than 11,000 children born between 2006 and 2013 in the region until they were 12 years old or until the end of 2022. The researchers estimated prenatal exposure to PFAS using water distribution records and parents’ addresses, and categorized exposure levels based on the parents’ addresses during pregnancy during the five years before birth. Children born to parents who lived in an address with contaminated water for all five years prior to the child’s birth were placed in the “very high” exposure category.
After adjusting for factors such as socioeconomic status and parental smoking, the researchers found that children with very high prenatal PFAS exposure levels had an approximately 40 percent higher risk of developing childhood asthma than children outside exposed areas. No increase was seen in children with high or moderate exposure.
“We didn’t see any effect in the vast majority of study participants,” said Anna Sakne Joad, associate professor of epidemiology at Lund University and another co-author. “We want to help people who are concerned understand what they need to worry about, but we also want to tell them what, to our knowledge, they don’t need to worry about.”
Tracy Woodruff, a professor of epidemiology at Stanford University who was not involved in the study, said the study was well-done and very interesting. The results are especially compelling because of the large sample size and the urgency of the focus, she said.
“This area of immune function is very understudied and undervalued in environmental health,” says Woodruff, a former senior scientist at the U.S. Environmental Protection Agency.
He said the situation was made worse by government inaction, a lack of investment in this area of research, and a failure to allow industry to provide enough data for scientists to understand how exposure to chemicals affects immune function. Woodruff noted that the Trump administration’s decision to eliminate the EPA’s Office of Research and Development is a blow to the understanding and regulation of PFAS contamination.
“The EPA is actively destroying some of the institutions critical to identifying toxic chemicals and their health effects,” Woodruff said.
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New research has its limits. One is to use addresses to approximate PFAS exposure, Bromberg said. Some exposure levels can be misclassified, and it is difficult to distinguish between in utero and childhood exposures, given that many of the children studied continued to live at the same address while drinking contaminated water.
“We can’t really say that the prenatal period is important because the children were still exposed when they were still young,” Blomberg said. “You can’t completely separate those effects.”
Blomberg and Joad said they hope this study can be replicated in other highly exposed populations around the world.
Woodruff said further research is important, but he also wants the government to clean up existing PFAS and prevent further contamination.
“We know a lot about PFAS exposure,” she said. “We need to take action too.”
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Keerti Gopal covers the intersection between climate change, public health, and environmental justice for Inside Climate News. Previously, we covered climate change activism and the suppression of movements. She is a National Geographic Explorer and has received fellowships from Fulbright, Solutions Journalism Network, The Lever, and the National Press Foundation.
