Relying on the term “forever chemicals” is part of the problem.

In the past four years, concerns about poly/perfluorinated alkyl substances (PFAS) have entered the agri-food industry amid media reports alerting consumers of yet another danger from the farm. As a result, the phrase “forever chemicals” has become a flashpoint among farmers, advisors and others involved in the debate. Late last year, it spurred demands for on-farm risk assessments and recognition within the U.S. Farm Bill.

Dr. Scott Mabury believes there has been a lot of hype and misinformation within general media reports about the seriousness of PFAS and their impact on farming and the environment.

“People fear what they don’t understand, and since chemistry is technical and often not well understood, it becomes easy to create fear or alarm,” says Mabury, vice-provost of academic operations at University of Toronto. “This is especially true when discussing anything around the production of food.”

Mabury’s background is as an environmental chemist. He also farms east of Toronto and he dislikes the “forever chemicals” brand that many have applied to PFAS, including media outlets.

According to a Government of Canada report in 2023, there are more than 4,700 human-made substances containing PFAS, a family of chemicals found in many household products, with fluorine chief among them. The list includes Teflon, pharmaceuticals and firefighting foams (aqueous film-forming foams (AFFF), stain- or water-repellent fabrics, food packaging and agricultural chemicals. The history of some PFAS products dates back to the 1950s.

Misunderstood
The reason for concern is the chemical make-up of certain products: some fluorinated chemicals are “extremely persistent” but some polyfluorinated chemicals are degraded in the environment. Mabury notes the use of land-applied municipal sewage compost has landed agriculture squarely in the middle of the debate.

“Many of the degradation products are the highly persistent perfluorinated acids widely observed in the environment, including human blood,” he adds.

However, a common challenge in the general population is equating detection to toxicity, which Mabury credits as part of the hype surrounding PFAS. Science can now detect the presence of compounds and elements via tests that didn’t exist 40 years ago, when pollutants in water were commonly measured in parts per million (ppm). Today, detection methods can measure most agents in parts per billion (ppb) and parts per trillion (ppt), with some now capable of parts per quadrillion (ppq or 1 x 10-15).

In translating it to time, if one part per million was equivalent to 11.6 days, one part per billion would be one second in 32 years and one part per trillion would be equal to one second in 31,709 years. But toxicity requires exposure, not just identification, and that’s where some degree of confusion and panic can occur.

Besides, as Mabury points out, the agri-food industry has moved to shorter-chained fluorinated materials which are generally safer. Nature is relatively efficient at processing many of the fluorinated products when released from consumer or industrial uses. Volatile fluorotelomer alcohols found in stain- and water-repellent materials and AFFF are detected in the atmosphere and can travel considerable distances but are usually degraded in the atmosphere.

In soil applications
With the application of municipal bio-solids, Mabury maintains their use will do more to meet crops’ nutrient needs and help to improve soil health than pose any serious risks due to PFAS. But that hasn’t deterred state and federal authorities in the U.S. from farmers and environmental advocates calling for “state and national action on PFAS”. That came in October 2023 in a request from a coalition of farmers from Maine, Michigan and New Mexico. In particular, Maine representatives demanded wider testing and monitoring of PFAS levels from agricultural activity. The drawback to that testing however, was that most required producers to cover the costs.

Prior to demands from that coalition, the Canadian Food Inspection Agency (CFIA) proposed an interim standard requiring biosolids contain less than 50 ppb of perfluoro-octane sulfonic acid (PFOS). According to testing from government and industry, more than 90 per cent of biosolids contained less than that level, which Mabury cited as “one of the most extensively produced, studied and measured” components. In tests of different materials, levels of PFOS were far below the 50-ppb threshold: municipal compost contained 0.75 ppb and beef manure tested below the lowest concentration to be quantified, at 0.33 ppb.

Mabury added that municipal compost (at 50 per cent dry matter) could be applied at 10 ton per acre. Since there are no established “safe soil” concentrations, at 0.75 ppb, it would take roughly 1,280 ton per acre -or 2,570 ton, as applied -for the average background concentration to double.

In background soils sampled in a six-inch soil profile across North America, PFOS ranged from 0.00004 to 0.0038 pounds per acre.