PFAS are almost everywhere. These “forever chemicals” are found in rainproof clothing, nonstick cookware, stain-resistant carpets, food packaging, shampoos, eye makeup, paints and sealers, ski wax and much more.
We’re exposed to PFAS in our homes, cars and workplaces every day, and it is not clear what the impacts are. Then why all the concern about PFAS in biosolids applied to farmland, where the concentrations are low and few people if any come into contact with them?
The worry is based on a very small number of farms where biosolids or sludges high in PFAS were applied before concerns about the compounds were known. On those farms, PFAS has ended up in livestock that eat the crops grown on the fields. There is also concern that PFAS can percolate down to groundwater, and in fact there are some “hot spots” where PFAS from industrial products like firefighting foams have done so.
The question is: Does that justify widespread curtailment or bans on land application of biosolids, creating serious and costly problems for clean-water utilities and depriving farmers of a highly beneficial product that enriches soil with organic matter and improves yields?
Last August the New York Times published an article[1] raising alarm about “sewage fertilizer” and the specter of PFAS “poisoning America’s land.” It caused consternation among clean-water professionals for the way it exaggerated the concern, essentially using a few anecdotes about PFAS hot spots to cast suspicion on the entire biosolids sector.
Compelling response
Among professionals responding to the article was Sally Brown, Ph.D., a research professor in the School of Ecosystem and Forest Sciences, College of the Environment, at the University of Washington, and a senior adviser to Biocycle magazine. Brown argues that humans exposure to PFAS through biosolids is trivial compared to exposure from everyday consumer products.
Brown’s research focuses on beneficial use of waste products and has worked on studies involving soil health, climate change mitigation, biosolids recycling and wastewater treatment. She believes that soil amendments including biosolids and composts, can help people and communities live more sustainably.
Recognitions for her work include the Rufus Chaney Research Award from the U.S. Composting Council, special recognition from the U.S. EPA, and the Green Globe Award for outstanding achievement in environmental stewardship from the King County (Washington) Department of Natural Resources and Parks.
She is a Fellow in the Soil Science Society of America and was a member of the National Academy of Science Committee on Soil Science. In an interview with Treatment Plant Operator, Brown shared thoughts on PFAS and their presence and impact in clean-water plant residuals.
TPO: Briefly, what is the background on your work with biosolids?
Brown: I got my Ph.D. working on heavy metals in biosolids, mostly cadmium, and then realized that biosolids could be used to fix metals-contaminated soils. So I began working less on contaminants and more on how we can best use biosolids. One thing I do is put together a library of research on topics pertaining to biosolids that is sent monthly to the regional biosolids associations. PFAS is a big issue, so it has been part of my job for the past 15 years.
TPO: How important is it that biosolids continue to be beneficially used?
Brown: Using biosolids is the most cost-effective thing a municipality can do with them. It is also the best option for soils and the planet. We have cities like Tacoma in Washington with Tagro and DC Water with Bloom, making biosolids products that are available to people with gardens. That results in drastic savings because they work so well that people pay for them.
TPO: What about benefits beyond simply saving on costs?
Brown: Environmentally, biosolids are amazing. It is much better for the environment to recycle nutrients we already have than to mine or manufacture new ones. First of all, by replacing synthetic nitrogen that is fixed from the atmosphere, there are big savings on energy and carbon emissions. Also, there are concerns about the availability of phosphorus, and so reusing that nutrient in biosolids is an excellent practice. And finally, because these nutrients are in an organic matrix, the plants and soils respond. Users get higher yields and healthier soils.
TPO: How common is it to find biosolids products with comparatively high PFAS levels?
Brown: It’s very uncommon, and the biosolids with high levels are generally legacy materials. The two PFAS compounds that have been banned, PFOA and PFOS, were mainly from manufacture of paper destined for food packaging. So the PFAS was in land-applied pulp sludges, or in biosolids from wastewater treatment plants that took untreated effluent from pulp mills that made food-service paper. You find high levels here and there, but is that a majority of biosolids? Absolutely not.
TPO: What is the best way to prevent that kind of PFAS contamination in biosolids?
Brown: The easiest way to control high levels of PFAS coming into a wastewater system is to do pretreatment. That is exactly what worked with metals in biosolids. You control the industrial discharges into the system.
TPO: How would you respond to the section of the Times article dealing with the farm in Michigan where beef cattle were allegedly contaminated?
Brown: The Times wrote a sensationalist article. You can look online and see how many farms there are in Michigan, and they found just one to talk about. The biosolids used on that farm were from treatment plants that had taken untreated effluent from chrome-plating industries. Michigan has had a very reasonable approach to PFAS. The state regulatory agency made all the utilities test their biosolids, and then they categorized them according to PFAS level. Then they ordered the utilities with the highest PFAS levels to stop land-applying biosolids until the PFAS concentrations came down.
TPO: Was anything done to mitigate those high levels?
Brown: Yes. They identified the industrial sources of the PFAS and required those industries to pretreat. I don’t know the exact success rate of that program, and I don’t remember the number of facilities that had higher than normal PFAS, but it was a minority, and most of those are back online with land application because they controlled the source inputs.
TPO: What happened in areas where high PFAS has been detected in groundwater?
Brown: About one-third of the United States has drinking water that’s above the EPA’s new PFAS standard. The sites with serious groundwater contamination are largely related to military bases and areas where firefighting foams were used.
TPO: The Times article raised the specter of widespread contamination of the nation’s farmland with high-PFAS biosolids. How would you put that issue into perspective?
Brown: In the United States, just over 50% of the biosolids produced, or about 3 million tons, ends up touching the soil each year. At a typical agronomic application rate of 3 tons per acre, that is enough biosolids for one million acres. Now compare that to 659 million acres grassland pasture, 390 million acres in crops, 132 million acres in grazed forest land, 6 million acres in farmsteads and farm roads and 74 million acres in urban land[2]. That million acres looks very small compared to well over a billion total acres.
TPO: The Times article also reported on a farm where beef cattle could not be taken to market because of high levels of PFAS in the meat. How would you respond to that concern?
Brown: If that farm family was eating beef just from those cattle, that’s a high exposure rate, depending on the PFAS concentration in the beef, which the Times didn’t report. But if that beef were sent to market and distributed to multiple supermarkets, what is the chance that any consumer would get more than one occasional serving that came from that farm? Again, it’s dilution, and the likelihood of a significant of exposure is minimized.
TPO: In an article you wrote for Biocycle[3], you used figures to put the risk of PFAS exposure from biosolids into perspective. How do PFAS levels in biosolids compare to levels encountered in household products and settings?
Brown: There are well over 12,000 varieties of fluorinated organic compounds. They are in our bodies and in everyday products. The average biosolids generated in California contains about 27,000 parts per trillion of PFAS. Meanwhile, dog poop contains 85,000 to 94,500 ppt. Dust in a home contains about 523,000 ppt, lipstick up to 1,560,000 ppt, and takeout food packaging up to 876,000,000 ppt. If you’re really concerned about PFAS, cook your meals at home instead of going to McDonald’s. Stop wearing makeup. Get rid of stain-resistant carpet.
TPO: How strong is the scientific evidence of actual human health effects from PFAS?
Brown: I am not an expert on that subject. I don’t know the science well enough. But it’s fair to say that nobody wants elevated PFAS. Why would you? I don’t think it’s a risk anybody should need to have, but banning biosolids is not the way to get rid of that risk.
TPO: What advice would you give to plant operators for dealing with PFAS in biosolids?
Brown: A first step is to test your biosolids to see if there is an issue. Then if you find PFAS at a level that is of concern, you can get your pretreatment staff to look at potential industrial dischargers, do some analysis and try to figure out where the PFAS is coming from.
TPO: What are some messages operators can use to help the public understand the issue?
Brown: The Times article was written in a way that could make people think treatment plants are the sources of this stuff. In reality, as an operator, you are at the wrong end of the pipe, the same as everybody else. You want PFAS in your biosolids as much as people want the PFAS in their blood. Let the public know that you are concerned, too. Be transparent and open about what you do, what your process is, where your biosolids go. You have nothing to hide. Be proud of what you do, because you should be. You’re protecting people from disease, you’re making the environment cleaner, and you’re making soils richer. Don’t lose sight of that.
References:
[1] Something’s Poisoning America’s Land. Farmers Fear ‘Forever’ Chemicals, Hiroko Tabuchi, New York Times, August 31, 2024, https://www.nytimes.com/2024/08/31/climate/pfas-fertilizer-sludge-farm.html?searchResultPosition=4.
[3] Connections: Facts vs. Fear Mongering, Sally Brown, Ph.D., BioCycle, https://www.biocycle.net/connections-facts-versus-fear-mongering/.
