Just passing through: The life cycle of PFAS

It’s hard to escape a day without seeing something related to per- and polyfluoroalkyl substances (PFAS), a group of synthetic compounds used in a wide range of manufacturing and linked to serious human health concerns. Just the other day, I saw an article by the Keck School of Medicine of the University of Southern California about a study linking PFAS levels in the bloodstream of study participants to tea consumption. Of course, I was reading this as I was drinking my daily serving of iced green tea. This article had me thinking about the PFAS around (and in) us and what will eventually happen to them.

I have accepted the fact that PFAS compounds are in my blood. My next logical thought was how long PFAS would remain in my blood. Our bodies are constantly trying to remove toxins, but a particular problem with PFAS is that they tend to accumulate in our bodies more quickly than they are excreted. A recently published review of various studies estimating the half-life of PFAS compounds in humans found the mean half-life for various PFAS compounds ranged from 1.48 to 8.5 years. I was relieved to read that, if I stopped my green tea PFAS habit (assuming my specific tea bags contained PFAS), I could be PFAS-free in 17 years or less. Something to look forward to.

Fortunately, efforts are being made in the U.S. and worldwide to phase out the use of PFAS in everyday products. Eventually, we will live PFAS-free lives. But until these compounds are completely removed from manufacturing processes, we commonly are left to dispose of PFAS-containing products in two ways: through the sewer or the landfill.

What happens, then, with all the waste containing PFAS that has been disposed of and contained in the landfill? What is the fate of PFAS in the landfill? Similar to what happens in our bodies, PFAS accumulates in the landfill and is slowly “excreted,” mainly through leachate removal but also to some extent through landfill gas. A September 2023 article estimated that 10 percent of PFAS entering landfills annually is emitted through leachate and 6 percent through landfill gas. The remaining 84 percent is accumulated in the landfill. While I am comforted to know that most PFAS are contained within the landfill, the fraction that makes its way into leachate and landfill gas is concerning for our environment.

A standard tool for determining what happens to waste in a landfill is the Environmental Protection Agency’s Method 1311, “Toxicity Characteristic Leaching Procedure,” or TCLP. I am not going to argue for or against the use of TCLP in assessing the leachability of PFAS from waste as plenty of research needs to be completed in this area. I do know from some analyses I performed (very few samples disclaimer) that wastes containing PFAS leached approximately 10 percent of their PFAS mass during the TCLP test, similar to the study referenced above.

The connection between the published articles I have cited here raised my interest. More research will be done in this area to further characterize the leachability of PFAS compounds and their mass flux through the landfill over multiple years. I’m certain scientists and researchers will develop a model to determine the mass balance of PFAS disposed at, sequestered in and emitted from a landfill on an annual basis. This will help landfills plan for leachate pretreatment and landfill gas treatment to remove PFAS from their emissions.

Currently, most landfills in the U.S. do not treat these emissions to remove PFAS. Many landfills, especially smaller municipally owned facilities, have not planned for costly PFAS treatment of leachate and landfill gas. The bulk of the PFAS emitted from municipal solid waste landfills ends up at local, publicly owned treatment facilities. Some will end up in biosolids and be returned to the landfill for another round of leaching, while the rest will be discharged to the environment in the treatment facility’s effluent.

My hope is research will show that, at some point, PFAS will remain sequestered in the landfill with diminishing amounts of PFAS being leached. And, that the research is correct—the PFAS compounds in my bloodstream are just passing through.