The research team found that total particle-phase PFAS concentrations in Huntsville ranged from 110 to 130 picograms per cubic meter, approximately 5.5 times lower than the concentrations measured in Houston.
As concerns grow nationwide about the health and environmental risks posed by persistent “forever chemicals,” new research at The University of Alabama in Huntsville (UAH) is bringing the issue closer to home, revealing compounds in airborne particles collected in Huntsville, Ala., carry a distinct chemical signature that may reflect nearby industrial and military activities. Research led by UAH scientists at UAH, a part of The University of Alabama System, has found evidence of persistent per- and polyfluoroalkyl substances (PFAS), commonly known as “forever chemicals,” in airborne particles collected in Huntsville.
The study, published in ACS ES&T Air, compared airborne PFAS collected in Huntsville and Houston, Texas, and found that the two cities had markedly different chemical profiles. In Huntsville, long-chain PFAS compounds, including perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA), predominated in the samples. These compounds have been phased out of U.S. production but can persist in the environment long after their original use.
“What was surprising was that most of what we saw were legacy long-chain compounds, such as PFOA and PFNA, that are no longer produced in the U.S.,” says Dr. Shanhu Lee, a professor of Atmospheric and Earth Science and co-author of the study. “We did not see the newer replacement PFAS such as GenX.”
The research suggests that legacy PFAS can continue entering the atmosphere from older products, contaminated soil and water and industrial sites long after production has stopped.
“With the 3M and Daikin America fluoropolymer plants in Decatur, only about 15 miles from our site, it is quite expected to see PFAS in the air,” Lee explains.
PFAS are synthetic chemicals used in a wide range of industrial and consumer applications, including water- and stain-resistant textiles, grease-resistant food packaging and firefighting foams. Their persistence in the environment and associations with adverse health effects, including increased cancer risk, have raised concerns about human exposure through contaminated food and water. Inhalation of PFAS in ambient and indoor air is another potential exposure pathway, although the extent of exposure through air remains incompletely understood.
The research team found that total particle-phase PFAS concentrations in Huntsville ranged from 110 to 130 picograms per cubic meter, approximately 5.5 times lower than the concentrations measured in Houston. However, the composition of the chemicals differed substantially. In Houston, short-chain perfluoroalkyl carboxylic acids dominated the PFAS profile, consistent with patterns reported in many urban environments. In Huntsville, the distribution was reversed, with longer-chain compounds predominating.
PFAS can move between the gas phase and airborne particles as environmental conditions change, allowing the chemicals to travel through the atmosphere and reach locations far from their original sources.
“PFAS are semivolatile, so they move back and forth between the gas and particle phases as they travel,” Lee notes. “Once emitted, they can travel to different locations. That is why PFAS are ubiquitous.”
Advancing real-time PFAS monitoring
In addition to comparing the two cities, the researchers demonstrated the value of an emerging approach for monitoring atmospheric PFAS. The team used an iodide chemical ionization mass spectrometer (I-CIMS) to measure PFAS in both the gas and particle phases in Houston at intervals of a few minutes. Traditional laboratory methods often rely on collecting samples over extended periods and analyzing them later. Although these methods can identify and quantify specific compounds with high accuracy, they may not capture rapid changes in atmospheric chemistry.
The I-CIMS approach offers a way to observe those changes as they happen. The researchers validated the technique against targeted laboratory analysis using liquid chromatography-electrospray ionization Orbitrap mass spectrometry. The researchers confirmed the accuracy of their real-time monitoring technique by comparing their results with those from an established laboratory method for detecting PFAS.
The measurements revealed that gas-phase PFAS concentrations tracked changes in temperature and ozone, while particle-phase concentrations were associated with humidity. These findings help explain how meteorological conditions influence whether PFAS remain airborne as gases or become associated with particles.
The researchers also found that humid conditions can favor the uptake of PFAS into water-containing airborne particles. This process may be particularly important in warm, humid urban environments, with implications for atmospheric transport, deposition and potential inhalation exposure.
The study involved UAH Ph.D. students Vignesh Vasudevan-Geetha and Zach Watson, research scientist Lee Tiszenkel, a UAH alumnus, and collaborator Dr. James (Jimmy) Flynn of the University of Houston.
For Lee, communicating the findings to the public is an important part of the research mission, as the results will encourage community members to ask questions about PFAS emissions and consider ways to reduce the use of these chemicals.
“Knowing the truth is the first step of mitigation,” the researcher says. “I hope this finding will encourage community members to have more proactive/active conversations about PFAS in the air we breathe and help reduce PFAS use in industry and in our daily lives. So many consumer products contain PFAS.”
The next goal is to investigate seasonal variations in Huntsville’s atmospheric PFAS concentrations to better understand how these compounds are emitted and how their presence in the air changes throughout the year.