Farming through forever chemicals: Maine’s approach to PFAS contamination

Maine has emerged as a national leader in researching and responding to per- and polyfluoroalkyl substances (PFAS) contamination in agricultural land.

While PFAS contamination has impacted dozens of Maine farms, even causing some to permanently cease operations, Duncan Pfaehler, a senior planner with Maine’s PFAS Response Program, said, “This is not the end of the world. We just need to be precise about how we handle it.”

PFAS, also known as forever chemicals, are a class of thousands of manmade chemicals that have been used for decades in many consumer and industrial products. Their heat- and water-repellent properties are useful in products like firefighting foams, carpets, upholstery, non-stick cookware and water-repellent clothing. But these properties are also what cause PFAS to persist in the environment, and they are associated with numerous health risks including an increased risk of liver and thyroid disease and kidney and testicular cancers.

Maine first began investigating PFAS contamination at farms in 2016 when milk at a dairy farm in southern Maine was found to have high levels of perfluorooctane sulfonate (PFOS), a type PFAS.

Since that discovery, Maine has taken a proactive approach to measuring PFOS on farmland where biosolids spreading occurred. Testing of soil, water, crops and agricultural products has been extensive and ongoing.

PFOS is the most prevalent PFAS compound found in contaminated ag systems, according to Pfaehler. Among the thousands of different PFAS compounds, PFOS consistently shows up as the dominant contaminant on affected farms and readily transfers through the agricultural food chain.

“That application of sludge is then taken up into crops, which then goes to our livestock and then into our food supply and ultimately into us,” said Pfaehler.

In the absence of federal standards, Maine has established state-specific PFOS action levels for three agricultural products: milk, beef and chicken eggs. These are regulatory thresholds that require immediate cessation of sales when PFOS levels are exceeded. For milk, the threshold is 210 parts per trillion (ppt); for beef, 3.4 parts per billion (ppb); and for chicken eggs, 4.7 ppb.

Maine is also supplementing the milk, beef and egg testing with non-enforceable soil screening levels to identify at-risk areas on the state’s farms. A screening level is a threshold concentration that determines whether further investigation is warranted. For PFOS, the most conservative agricultural soil screening level is 6.4 ppb. At this time, Maine has not established guidelines for safe levels of PFAS (or PFOS) in produce intended for human consumption.

One of Pfaehler’s jobs is to communicate with farmers about their options and mitigation strategies after they receive PFOS test results. He stressed that a one-size-fits-all approach was not effective. According to Pfaehler, every farm is unique, requiring different site-specific investigation, sampling and customized mitigation strategies.

“I think the most important message that I want to tell folks, and especially farmers, is that farms can continue operating and producing safe food despite having PFAS on their property,” he said.

PFAS mitigation will vary depending on the farm type and the source of contamination. The PFAS Response Program offers financial resources to help pay for these strategies, as well as PFAS testing and more. Since there are no proven methods for reducing or removing PFAS from soil, most efforts are related to managing a farm’s water and soil resources and adapting crop plans.

Reducing PFOS levels in water means filtering contaminated groundwater from wells and drilling new wells in uncontaminated areas to provide clean drinking water for livestock and crops.

Other strategies relate to feed management, such as switching to crops with lower PFAS uptake. On a livestock farm, this can be accomplished by transitioning from corn silage to snaplage or grain corn in contaminated fields. This is effective because reproductive plant parts like seeds and grains have a lower propensity to accumulate PFOS than vegetative parts like leaves and stems. Similarly, a produce farmer might only grow leafy greens, which have a higher uptake of PFAS, on uncontaminated fields.

Livestock farms often have more options because animals gradually purge their bodies of toxins. Pfaehler said, “While we do hear about PFAS being ‘forever’ chemicals, they are not forever in our beef animals and our dairy animals. They do eventually rid these chemicals from their bodies. It just takes time and we have to cut off the source of that intake.”

For example, livestock farms can strategically feed forages with higher levels of PFOS during different stages of the lifecycle. Some farms put contaminated animals on clean feed for extended periods before slaughter. Pfaehler cited a farm that fed clean feed for four months prior to slaughter, with tissue samples showing reduction to acceptable levels in every animal.

In another example, he discussed PFOS levels at a dairy farm over a 1.5-year period. The levels started at 800 ppt, which far exceeded the threshold of 210 ppt. The farm was required to stop shipping milk, but the state worked diligently with the farm to identify the source of contamination and then reduce it. The PFOS levels then began to drop, and they were able to start shipping milk again.

This progress reflects extensive collaboration among state agencies, Pfaehler said. Agencies include the Maine Department of Agriculture, Conservation & Forestry, the Maine Department of Environmental Protection, the Maine Center for Disease Control & Prevention and University of Maine Cooperative Extension.

by Sonja Heyck-Merlin