Agriculture isn’t necessarily a source of PFAS, but PFAS have been discovered on farms.

PFAS is the acronym for per- and polyfluoroalkyl substances, also referred to as “forever chemicals,” that were first introduced in the early 1940s. Dr. Glenda Pereira, assistant professor and Extension dairy specialist, University of Maine, said USDA has identified 15,000 of these chemicals that were originally created to be oil-, water- and stain-repellant as well as heat resistant. PFAS are found in a variety of items including water-resistant jackets and high-temperature cookware. PFAS do not break down under normal environmental conditions and tend to accumulate in the body.

While PFAS have been in the environment for more than 60 years, data show more frequent PFAS exposure over the past 20 years. If a water source is contaminated with PFAS, humans or animals drinking the water will have higher than average contamination levels.

Some PFAS have decreased over time; others are more persistent. “We need to understand the source of contamination in food systems – wastewater sludge and septage, aqueous firefighting foam, Department of Defense sites, landfills and water,” said Pereira.

Although agriculture isn’t a source of PFAS, these substances end up in ag systems. “Farmers have used biosolids as a soil amendment for 30-plus years,” said Pereira. “When they were applying biosolids 30 years ago, we didn’t know there would be consequences from PFAS. In Maine, that’s one way a lot of farms have become contaminated.”

The question in Maine became “How do PFAS enter farms and how do they affect livestock?” PFAS in the soil are taken up by crops and consumed by livestock. Contaminated groundwater can impact crops fed to livestock, and PFAS-contaminated drinking water for livestock is another source.

“Dairy cattle that consume contaminated feed can become contaminated at various times in their life,” said Pereira. “Calves are contaminated by the dam in utero, then they’re fed that dam’s colostrum. Animals are also contaminated by forage during grazing, and when they come into lactation, expelling PFAS in milk even after a PFAS-free feeding period.”

Farmers have higher PFAS exposure if they’re near a potential contamination source. However, not all biosolids are contaminated with PFAS, so it’s important to check the source and history of biosolids.

In 2016 and 2017, PFAS were detected in milk on a dairy farm in Arundel, Maine. Rick Kersbergen, Maine Department of Agriculture, said the state assembled a team along with the Maine CDC to address PFAS on Maine dairy farms. A task force was assembled in March 2019.

“Maine Department of Agriculture, Conservation and Forestry did some store shelf testing,” said Kersbergen. “They tested milk to make sure food consumed by most Maine consumers was safe. That led to some detections, and we saw two farms with significant contamination.”

Maine DEP created a map that showed all licensed sites for sludge and septage in the state, which led to the detection of other sites in Maine that had problems related to PFAS in milk.

Kersbergen explained that certain products, including PFAS, are measured in parts per billion (ppb) and parts per trillion (ppt). “Maine is the only state with an established ‘adulteration level,’” he said. “The Maine Department of Agriculture has set that level at 210 ppt. The original farm with PFAS had 14,000 ppt.”

The half-life of PFAS in dairy animals is estimated to be 60 to 90 days. “While they’re ‘forever chemicals,’ they aren’t forever in dairy cows,” said Kersbergen. “Lactation is a good way to clean out a cow.”

One research project looked at how to determine farm-level PFAS issues and PFAS’s potential to contaminate milk. Kersbergen first tested soil, then plants, to determine the exposure pathway and the transfer factor.

“What does it take for soil to potentially contaminate feed, and how much feed is going to contaminate a cow and eventually the milk she produces?” said Kersbergen. “It’s been a challenge to figure out the transfer factor from soil to milk.”

Maine’s 2020 milk testing program was established to determine whether store shelf milk was safe, which it was. “We wanted to find out why we were getting some detections, and were able to trace them to two farms in central Maine,” said Kersbergen. “Farm A, an organic farm on which the previous owner had used biosolids, had a milk level of 20,000 ppt. Farm B had a milk level of about 800 ppt.”

Farm A had many fields with heavy PFAS concentration – greater than 200 ppb in the soil – which meant it would be difficult to grow clean feed. PFAS on Farm B were concentrated in one field, and the farmer had access to other clean fields for crop production.

The high-PFAS fields on Farm A were in pasture at the time of the PFAS discovery. All pastures were perennial swards with various pasture grass and legume species. Kersbergen noted higher transfer factor levels in second and third forage cuttings.

“The reason for that is we see a lot of higher concentration of PFAS in the leaves of grasses versus the stems,” he said. “Second and third cuttings have higher leaf-to-stem ratios.”

Perennial forages have higher potential for residual soil in forages, which may contribute to higher PFAS in the feed. Kersbergen said one recommendation is when filling silos with forage, layer feeds from various fields to dilute PFAS in the total ration.

Because corn tends to have a lower plant uptake of PFAS, Farm A converted all highly contaminated pasture acreage to corn silage. Researchers theorized that snaplage, which includes the grain, husk, cob and the shank of the corn plant, would have lower PFAS levels.

“Management is a factor in eliminating peaks and valleys in milk contamination,” said Kersbergen. “Another spike occurred when a group of heifers entered the milking herd. They had consumed contaminated feed, were not yet lactating and stored PFAS until they started producing milk. If heifers have had potentially contaminated feed, withhold their milk.”

The best approach when managing PFAS on farms is to start with the soil, but this can be challenging regarding sampling and where biosolids were stored. Assistance is available to Maine farmers who suspect PFAS on the farm.

An EPA grant will assist the University of Maine Livestock & Forage Systems Engineering team in ongoing PFAS research on farms. Also benefitting from the EPA grant are the University of Virginia, University at Albany/SUNY, Temple University (in Pennsylvania) and the Passamaquoddy Tribe of Pleasant Point, Maine.

by Sally Colby