Some landfill 'burps' found to contain airborne PFAS

Many municipal landfills ‘burp’ gas from decomposing organic matter rather than letting it build up — and burps from buried waste containing per- and polyfluoroalkyl substances (PFAS) can release these chemicals into the air. That’s according to a new study published in the journal Environmental Science & Technology Letters, which reports unexpectedly high levels of airborne PFAS at three landfills and demonstrates that vented gases and liquid by-products called leachates could transport similar amounts of these contaminants to the environment.

Some consumer products and commercial waste, such as children’s clothing, cosmetics and wastewater treatment sludge solids, contain PFAS — and they ultimately end up in landfills. Timothy Townsend and his colleagues at the University of Florida previously established that PFAS-containing waste can contaminate the water that seeps through landfills; this leachate is usually captured and treated before entering the environment.

Landfills also produce gas that can be captured and controlled, but unlike leachate, it’s often released untreated. The burped gas is mostly made up of methane and carbon dioxide; however, two recent studies also discovered a subset of airborne PFAS called fluorotelomer alcohols, which have the potential to be toxic when inhaled and can be transported long distances. Since the prevalence of PFAS-contaminated landfill vapours isn’t yet widely known, Townsend and his team wanted to identify and measure them in vented gas at three sites in Florida.

The researchers pumped landfill gas from pipes through cartridges filled with resin that captured the airborne PFAS. They freed the compounds from the cartridges with organic solvents and analysed 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 previous studies at other landfills. Three of these alcohols (abbreviated 6:2, 8:2 and 10:2) comprised most of the vaporised contaminants measured at each site.

The researchers also collected leachate samples at the Florida sites and analysed them for ionic PFAS commonly found in water samples. From this data, they estimated that the annual amount of fluorine (as a proxy for PFAS content) leaving the landfills through gas emissions could be similar to, or even greater than, the amount leaving through leachates.

Because landfills are repositories for PFAS, this work indicates that vented gas from these sites should be considered in future mitigation and management strategies to reduce potential inhalation exposure and release to the environment. Some landfills burn the vapours or trap them for energy production, and the team suggests that further research is needed to determine the degree of removal these treatments provide for airborne contaminants.

Image caption: Landfill burps from three sites in Florida, such as this one, contain high levels of airborne PFAS, including fluorotelomer alcohols. Image credit: Ashley Lin.