Exploring How PFAS in Wastewater Irrigation Impacts the Entire Food System
Farmers using treated wastewater for irrigating their crops have found a viable way to get additional nutrients to their fields while reducing reliance on synthetic fertilizers. This practice has been around for decades, but does it have a seedy underside that’s potentially damaging to food animals and humans?
Kelly Kosiarski, a Ph.D. graduate assistant at Penn State University and student ASABE member, presented about polyfluoroalkyl substances (PFAS) in treated wastewater used for irrigation and its effects on plant health at the ASABE Annual International Meeting.
If you’re not familiar, PFAS are synthetic chemicals with carbon-fluorine bonds—the fourth strongest bond in chemistry, to be exact. These extremely strong bonds make PFAS undegradable, yet they’re found in more than 7 million different consumer products. Some common products that have PFAS are pharmaceuticals, non-stick cooking pans and personal care products like makeup, including foundation. Wastewater treatment cannot remove some contaminants like PFAS, so they make their way into the water cycle.
Farmers using treated wastewater with high levels of PFAS can cause negative impacts on entire ecosystems, including drinking water, livestock, humans. Kosiarski’s research aimed to determine the biggest pathways for PFAS exposure in crops—foliar absorption compared to root uptake in corn and orchard grass, two common forage sources for cattle. Kosiarski’s study estimated the amount of PFAS a cow might be exposed to throughout a year of eating that forage, and what that might mean for consumers.
Treated wastewater is typically irrigated into fields through spraying, which covers both the plants and the soil profile. Water in the soil is taken up through the roots. But which approach has the most negative impact on the crop?
Kosiarski’s study conducted a weekly intake calculation of the cows’ forage intake. Because no benchmarks were available for livestock, their benchmark was recommendations set by the European Food Safety Authority (EFSA), which sets tolerable weekly amounts of PFAS for humans.
The results found that crops typically absorb more PFAS through taking water up in their roots. The good news for crop growers is that there weren’t any adverse plant health effects. Plants have a much higher tolerance to PFAS than humans, because of their cell structure and lignin. PFAS can look like fatty acid molecules to the human body, bind to transporter proteins and have to be metabolized differently, so the human body has a difficult time processing them. Studies have also shown that PFAS cause vaccines to have decreased immunity in humans.
Cattle eating those forages were exposed to PFAS levels exceeding the tolerable weekly intake for humans. Kosiarski’s research was unable to explore further what the bioaccumulation of PFAS means for humans.
This research is a great foundation for future studies on how PFAS interact with ruminant digestive systems, how PFAS affect calves and cattle’s responses to vaccines.