Pine needles can contain toxic PFAS compounds, according to NC State study

Pine needles don’t lie.

Scientists at NC State University have detected more than 70 types of toxic PFAS in pine needles, including extremely high levels of several compounds in needles collected near Raleigh-Durham International Airport.

The findings, and others detailed in a recent study, could help scientists “fingerprint” the compounds and trace them over time to their original sources.

Since the needles have a waxy coating whose function is to protect the tree, pollutants, such as PFAS, can accumulate in them. This can occur either through the air or in uptake through the soil.

The scientists collected and analyzed needles from loblolly and longleaf pine trees in six North Carolina counties: Brunswick, Cumberland, Durham, Onslow, Robeson and Wayne. Some needles were gathered within the past five years; others were much older. Because PFAS persist in the environment for decades — earning them the nickname “forever chemicals” — scientists found the compounds in pine needles that had been stored in university collections since the 1960s.

The needles were then dried at low temperatures so as not to remove any PFAS.  After extracting the PFAS from the needles, scientists used mass spectrometry, which analyzes chemical substances according to certain properties, to determine their concentrations and their type.

The scientists found that the number of compounds detected increased over time. That trend aligns with manufacturing practices. Only a few types of PFAS were made in the 1940s. Now roughly 9,000 types have been produced.

PFAS, also known as perfluorinated and polyfluoroalkyl compounds, are widespread in the environment. They have been manufactured since the 1940s, and are found in consumer products, such as microwave popcorn bags, Teflon cookware and water-, stain- and grease-resistant materials. 

Chronic exposure to PFAS has been linked to multiple health effects, including several types of cancer, thyroid disorders, depressed immune systems, reproductive issues and problems with fetal development.

There were also interesting patterns in where certain types of PFAS were found.

“Extremely elevated levels” of three types — PFSA, PFCA and PFASA — were found only in needles collected near RDU Airport.

“That surprised us,” said chemist Kaylie Kirkwood, one of six scientists who worked on the study. “Once we got the results were knew we had to go back and really get a full picture.”

Another compound, PFECHS, was detected only at sites near RDU. This compound was a replacement for PFOS, which has been phased out. It is considered as an essential for use in aircraft hydraulic fluids. 

Compounds were also found in tree needles near a National Guard facility adjacent to RDU. “They were the highest levels we saw in the entire study,” Kirkwood said.

Needles from trees near the Fayetteville Regional Airport had different types of PFAS than those found at RDU. These were a type of chlorofluoroether, which Chemours reportedly does not use or make. Scientist theorized that the compounds found at the Fayetteville airport are likely a “component of materials at the air port or another unknown source in the area.”

Since 1960, the military and the aviation industry have used firefighting foam that contained PFAS, both to extinguish blazes and in training exercises. That could also explain why a spike of the compounds were found in pine needles originating in Wayne County in 1967. Seymour Johnson Air Force Base is located in Goldsboro, in Wayne County.

Predictably, there was an uptick in PFAS in needles near of the former DuPont plant, now Chemours, on the Bladen-Cumberland County line. DuPont began discharging PFAS into waterways and the air in 1980. Over the next 30 years, needles from trees within two miles of the plant showed the presence of PFAS, including two that are very specific to Chemours plant: GenX and Nafion Byproduct 2. 

However, the study results showed that there is a “decreasing trend” in the abundance of PFAS  in pine needles near Chemours, likely the result of state regulators requiring the company to rein in its emissions and discharges.

The scientists limited their research to detecting PFAS in the needles. (For areas with different tree types, eucalyptus and other plants could be used.) It’s unclear what becomes of the PFAS once the needles fall to the ground — or are used for plant mulch. Presumably, the compounds would enter the soil as the needles decomposed.

The study has could be expanded to learn how quickly PFAS accumulate on the needles, for instance, after a chemical spill. Or trees could be planted close together around a manufacturing plant to study how wind patterns affect how PFAS travel in the air.

“I don’t think we were trying to like instill any panic about pine needles,” Kirkwood said. “We were more wondering how can we use something that is already accumulating — PFAS — and  to learn more about it.”

Kirkwood was joined by fellow scientists Jonathan Fleming, Helen Nguyen, David Reif, Erin Baker and Scott Belcher on the research. The results were published in February in Environmental Science & Technology, a peer-reviewed journal.