The cool morning spring breeze hit Saundra Traywick "like a punch to the face."
Walking through her wooded 38-acre donkey farm in central Oklahoma, Traywick suddenly found it hard to breathe as the air smelled "toxic" and "like death."
Less than a mile away, a truck was spreading a chunky dark fertilizer on a hay farm, a familiar ritual in this rural community just beyond Oklahoma City's northeast suburbs.
But this fertilizer was putting off a smell that Traywick had never encountered. She soon discovered the fertilizer was made from processed sewage.
Converting sewage to fertilizer saves cities money on landfill costs, is a cheaper nutrient-rich fertilizer for farmers, and has become a billion-dollar industry for a handful of companies. However, biosolid fertilizer has been shown to contain chemicals that can harm the environment and human health.
"Essentially anything that goes down the drain ends up on these fields," said Traywick, who, months after first learning about biosolid fertilizer, urged the nearby town of Luther to ban it, which city leaders did in 2020.
Scientific studies are increasingly warning about the PFAS chemicals found in biosolid fertilizers. PFAS - short for per- and polyfluoroalkyl substances, also called "forever chemicals" - can be found in many water- and heat-resistant products, personal hygiene materials, medication and industrial waste.
But while some states have recently restricted or banned biosolid fertilizer entirely after finding it contaminated farmland and groundwater, Oklahoma lawmakers and environmental officials attempted to take steps this year to protect cities and corporations from liability if new health problems are found.
The EPA estimates that as much as 3.5 million dry metric tons of treated sewage waste is spread as fertilizer across the country yearly - enough to cover the entire state of Missouri.
Oklahoma has one of the most extensive biosolid fertilizer programs in the nation, as more than 80% of the state's wastewater sludge ends up on crop fields, according to Investigate Midwest's analysis of state records.
Synagro, a Goldman Sachs-owned company that spreads most of the biosolid fertilizer in Oklahoma and across the country, has lobbied against new regulations over "forever chemicals" in its fertilizer, even as it faces lawsuits from farmers claiming its product has devalued their land and created numerous health problems. "Biosolids are a nutrient-rich end-product of the wastewater solids treatment process that have been treated to ensure safe use in agricultural land application," the company said in a statement.
The issue has also taken center stage in an Oklahoma state House race, as a longtime lawmaker who uses biosolid fertilizer on his land risks losing to a challenger who wants to end the practice.
"I'd say it's one of the main issues," Traywick said about the upcoming state House election.
While scientists have discovered PFAS chemicals already exist in the blood of nearly every living person and animal on the planet, recent studies have raised concerns about increased PFAS exposure through its presence in biosolid fertilizers, which impacts the air, water and food.
Air: UCLA researchers found that microplastics in biosolid fertilizer are highly suitable to wind, "thereby increasing … inhalation health risks," such as lung tissue damage, according to a study published in January.
Water: Groundwater near biosolid fertilizer-applied fields often have elevated rates of PFAS, sometimes at higher rates than what is deemed suitable for human consumption, according to a 2024 study published by the American Chemical Society.
Food: In 2022, beef from a Michigan farm was contaminated with high levels of PFAS that officials said came from biosolid fertilizers.
