Release of “forever” chemicals into the air from landfills

Some landfill gas emissions contain PFAS, a class of pollutants colloquially known as “forever chemicals” because they are so difficult to remove from the environment once they have spread, according to a controversial new study.

Some commonly used products or their residues, such as clothing, cosmetics and wastewater sludge solids, contain perfluoroalkyl and polyfluoroalkyl substances (PFAS) that will eventually end up in landfills.

Timothy Townsend of the University of Florida in the United States and his colleagues had previously established that waste containing PFAS can contaminate water leaking from landfills. This leachate is usually captured and treated before it enters the environment.

Landfills also produce a gas that can be captured and controlled, but unlike leachate, it is often released untreated. The emitted gas is primarily made up of methane and carbon dioxide; however, two recent studies also discovered a subgroup of PFAS in the air called fluorotelomer alcohols, which can be toxic if inhaled and can be transported long distances. Because the prevalence of PFAS-contaminated vapors at landfills is not yet widely known, Townsend, Ashley M. Lin of the University of Florida, and colleagues decided to identify and measure them in gas released at three Florida sites.

The researchers pumped landfill gas from pipes through resin-filled cartridges that captured PFAS from the air. They released the compounds from the cartridges with organic solvents and analyzed the extracts for 27 neutrally charged PFAS, including fluorotelomer alcohols. Surprisingly, some of the fluorotelomer alcohol levels were up to two orders of magnitude higher than those found in previous studies at other landfills. Three of these alcohols (abbreviated 6:2, 8:2, and 10:2) made up the majority of the vaporized pollutants measured at each site.

Florida’s three-site landfills, such as the one adjacent to the photographed site where the measuring instruments were placed, contain high levels of PFAS, including fluorotelomer alcohols, which are released into the air. (Photo: Ashley Lin)

The researchers also collected leachate samples and analyzed them for the presence of PFAS ions commonly found in water samples. From this data, they calculated that the annual amount of fluoride (as a proxy for PFAS content) leaving landfills through gas emissions could be similar to, or even higher than, the amount leaving leachate.

Since landfills are reservoirs for PFAS, this new study indicates that the gas released from these sites will need to be considered when planning future mitigation and management strategies to reduce potential inhalation exposure and release into the environment.

At some landfills, fumes are burned or trapped for energy production. However, the team says more research is needed to determine how much air pollutant removal these treatments provide.

The study is titled “Landfill Gas: A Major Pathway for Neutral Per- and Polyfluoroalkyl Substance (PFAS) Release.” It was published in the academic journal Environmental Science & Technology Letters. (Source: American Chemical Society)