PFAS and agriculture: What it means

The Dairy Voice podcast, from the NDHIA’s media partner, Dairybusiness.com, recently hosted a discussion on a relatively new and emerging concern for the dairy industry: per- and polyfluoroalkyl substances (PFAS). These manmade chemicals are known as “forever” chemicals, and have caused undo hardship on a dairy farm in New Mexico, as well as one in Maine, both of which were found to have high levels of contamination in their milk. Detectable levels of PFAS have also been found on numerous dairy farms in Michigan, one of a handful of states which have been testing for these chemicals to see just how ubiquitous they are.

This isn’t just a dairy problem. PFAS are cropping up in soils, water, food and feed across the nation. But PFAs aren’t farm-derived. These synthetic chemicals, which do not readily break down and therefore can continue indefinitely and accumulate in the environment as well as in our bodies, are commonplace in consumer personal care products and household goods. They are detectable and commonly found in our bloodstream.

PFAS repel oil and water, are temperature resistant, and decrease friction. They are found in common household clothing and fabric items that are stain resistant or water repellent, and in non-stick cookware. They are found in cleaning products and waxed dental floss, and in food packaging. And they are now being tested for and found in food itself, in soils and water, and in our bodies, typically at low levels.

The reason PFAS are so formidable is the bond between the carbon and fluorine atoms, which is “actually the strongest bond in nature,” environmental engineer Matt Schroeder, of the Dragun Corporation in Michigan, said on the podcast. “We’ve found that they have some potentially some health issues at some very low levels.”

But how are they finding their way onto our farms?

PFAS may have negative health effects in the part per trillion range, and the Food and Drug Administration (FDA) has begun testing for these chemicals — there are more then 5,000 — in foods.

Dairy concerns?

In 2016, the FDA tested milk samples, with no PFAS found in 49 samples commercially available milk tested. Raw milk samples included one of 12 with PFAS at detectable levels. That one farm had applied biosolids to their fields.

Field application of biosolids may be a concern for dairy farmers moving forward. But the biggest dairy farm contamination — that in New Mexico — occurred on a farm located next to an Air Force base, where aqueous film forming foam, a firefighting product loaded with PFAS, contaminated ground water. Other contamination situations have occurred in proximity to manufacturing plants where PFAS are produced or utilized in production.

According to the North East Biosolids and Residuals Association website, “typical biosolids with no direct large industrial inputs are unlikely to impact ground and surface waters at levels above U.S. EPA’s health advisory level for drinking water (70 ppt).”

Wisconsin attorney Leah Ziembra, also interviewed on the podcast, advises dairy farmers to “remain level-headed about this,” and to examine “the risk profile on your operation. There’s a lot of information about sites” known to be high risk for PFAS contamination.

Biosolids sourced from a treatment plant accepting wastewater from a primary PFAS user are the primary concern. Farms located in proximity to these sources should also be concerned about PFAS levels in their soil and ground water.

Scientific perspective

Dr. Linda Lee, of Purdue University, holds a doctorate in soil chemistry and contaminants hydrology, and is an expert on PFAS. She was recently featured on the Water Environment Federation’s Words on Water podcast.

PFAS are very water soluble, with shorter chained PFAS more soluble than the longer ones. PFAS also are unstable in the manner in which they move through soil profiles, and the soil/water interface — the zone where crops grow — is particularly problematic. PFAS do not move quickly through this zone, and “PFAS do weird things” while there, Lee said.

Biosolids are derived from wastewater treatment plants, where water from residential, commercial, industrial and other uses are treated and separated into sludge and effluents, along with a small percentage of volatile material which is released to the air, Lee explained. Although PFAS dissolve in the effluent, the dilution effect keeps their levels low, so they don’t tend to accumulate in our rivers and fish at unacceptable levels.

“The problem with biosolids is that they have really high nutrient value, (and) high carbon value, to them. They’ve been land-applied for decades,” before there was any concern about PFAS. Today, we primarily need to investigate “how much is the land-applied biosolids contributing to our total load of PFAS in our drinking water, and our food system,” Lee said.

Biosolids are a resourceful way to recycle our own waste, and to help combat climate change via carbon sequestration. Lee believes that the benefits of biosolids production and reuse as soil amendments outweigh the PFAS risk, as biosolids are not normally a source of PFAS contamination. The issue comes from industrial contamination from manufacturers of PFAS, or heavy users of products in which the chemicals are found, such as airports.

“I suspect that at least 95 percent of biosolids that get produced by municipal plants have…relatively low PFAS loads, that when they are land-applied are not going to be significant,” Lee said.

Dilution of land-applied PFAS, by mixing biosolids with other materials to meet the nitrogen needs of the land, is recommended. If biosolids were simply applied based on land nitrogen needs, it could require a large amount, maximizing PFAS load on the land.

The PFAS in land-applied biosolids don’t disappear, Lee said. Those with smaller chemical chains are more mobile, while the longer chained PFAS tend to stay in the soil and accumulate. Large PFAS do very slowly degrade into smaller PFAS. The key is to keep the PFAS load from biosolids low enough, via dilution with other materials, to allow this degradation process to occur, so the total PFAS load of the soil remains within regulatory limits. The half-life of long chain PFAS is about five years.

If effluent from water treatment plants is used for irrigation of crops, some PFAS volatilize into air. Most remain in the soil until they hit groundwater, or are discharged in tile drainage, Lee said.

Short chain PFAS from biosolids or effluent are taken up by crops, or move into groundwater. But these have shorter half-lives, and much higher concentrations are needed to reach levels where adverse health effects are of concern, Lee said.

Another issue is the use of any crops where PFAS are detected. Are these crops being directly consumed by humans, or are they being used for animal feed? Will the PFAS accumulate in livestock over time, to unsafe levels, and then be found in their milk or meat?

All of these questions, and more, still need to be quantified. Keeping the direct-to-body levels of PFAS, measured in parts per trillion, very low is the key to mitigating any adverse health effects, Lee emphasized.

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