Environmental factors contribute to higher PFAS exposure in Southern California

Evidence is mounting on the health problems linked to per- and polyfluoroalkyl substances (PFAS), a group of manufactured chemicals used in consumer products that accumulate in the body and take a very long time to break down. These substances increase risk for a number of medical concerns, including cancer, liver damage and fertility issues.

In a study funded in part by the National Institutes of Health and the USC President's Sustainability Research Initiative, researchers from the Keck School of Medicine of USC explored whether drinking water, food access and industrial pollution were linked to differences in blood levels of PFAS among 446 Southern California residents. It is one of the first studies to analyze PFAS in relation to certain neighborhood factors, including food access and proximity to Superfund sites-;areas designated by the U.S. Environmental Protection Agency (EPA) as contaminated with toxic substances.

Instead of placing the burden on individuals to avoid PFAS, we're looking at neighborhood factors beyond their control. How can we improve our neighborhood environments to reduce PFAS and the associated disease risk?" 

Shiwen (Sherlock) Li, PhD, first author, postdoctoral researcher in the Department of Population and Public Health Science, Keck School of Medicine

Several factors were associated with higher levels of PFAS in the blood. These include living in a neighborhood with low food access, living in a water district with PFAS contamination, and living within a three-mile radius of a PFAS-polluting facility or Superfund site. The results were just published in the journal Environmental Research.

Because participants in the study were primarily Latino, the findings provide evidence for the power of addressing neighborhood-level factors in reducing racial and ethnic environmental health disparities. 

"We're adding a different perspective to solving the PFAS problem, because the risk to exposure of PFAS at the neighborhood level is not evenly distributed," Li said.

Mapping PFAS contamination

Li and his colleagues started with a simple question: What neighborhood factors predict differences in blood levels of PFAS? After obtaining blood samples and residential addresses from two predominantly Hispanic participant groups, the Metabolic and Asthma Incidence Research Study and the Study of Latino Adolescents at Risk, they conducted a series of analyses to dig deeper.

Using data on drinking water contamination from both the EPA and the state of California, the researchers found that people who lived in areas where perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) or perfluorohexanesulfonic acid (PFHxS) was found in drinking water had higher levels of those substance in their blood: a 1.54 nanogram per milliliter average increase for PFOS; 0.47 ng/mL for PFOA; and 1.16 ng/mL for PFHxS, compared to people living in areas without PFAS-contaminated water. The national averages for those PFAS range from about 1 to 6 ng/mL, so the increases are substantial, Li said.

Because PFAS are commonly found in food packaging, the researchers also explored whether low access to fresh food related to PFAS exposure. They used data from the U.S. Department of Agriculture, which defines low food access as a census tract where more than 500 people or one-third of the population live more than 0.5 miles from the nearest supermarket. They found that people living in neighborhoods with low food access had higher levels of PFOS, PFOA and perfluoroheptanesulfonic acid (PFHpS) in their blood (2.51 ng/mL, 0.6 ng/mL and 0.06 ng/mL, respectively), likely because they were more apt to consume packaged foods, Li said.

Finally, researchers studied whether living near a designated Superfund site or an industrial site known to process PFAS was linked to higher blood levels of PFAS. They found that for each industrial site processing PFAS within a three-mile radius, blood levels of PFOS increased. Living near a Superfund site predicted higher levels of PFOS, PFHxS, PFHpS and perfluoropentanesulfonic acid (PFPeS) in the blood.

Raising awareness on PFAS risks

New EPA rules are changing the way PFAS are regulated. Starting in 2024, these chemicals were included on the list of hazardous substances that can lead to a "Superfund site" designation, opening up additional funding for toxic waste cleanup. Another new rule, set to take effect in 2029, will regulate the levels of six PFAS in public drinking water.

"But in the meantime, those water systems are still contaminated with PFAS, and a lot of people don't know they live in a neighborhood with water contamination. So, the first step is to raise awareness," Li said. The Keck School's Department of Population and Public Health Sciences has launched several community engagement efforts to share their research findings with people living in high-risk areas.

Next, Li and his team will explore PFAS exposure near chrome plating facilities, which use high levels of PFAS in their manufacturing processes.