It’s literally raining “forever chemicals” in Miami

PFAS are in Miami’s rainwater. And it is the latest evidence the synthetic “forever chemicals” — that have raised health concerns for people and wildlife — hitch a ride on the water cycle, using the complex system to circulate over greater distances.

For more than a year, FIU researchers collected and analyzed 42 rainwater samples across three different sites in Miami-Dade County. A total of 21 perfluoroalkyl and polyfluoroalkyl substances, or PFAS, were detected, including PFOS and PFOA (since phased out of production over cancer concerns), as well as the newer varieties used in manufacturing today.

While profiles of several PFAS matched back to local sources, others did not. According to the study, published in Atmospheric Pollution Research, this suggests Earth’s atmosphere acts as a pathway to transport these chemicals far and wide — contributing to the worldwide pollution problem.

“PFAS are practically everywhere,” said FIU Assistant Professor of Chemistry and study author Natalia Soares Quinete. “Now we’re able to show the role air masses play in potentially bringing these pollutants to other places where they can impact surface water and groundwater.”

Widely used in consumer products — non-stick cookware, clothing, cosmetics, food packaging, detergents and firefighting foams, to name a few — PFAS were purposefully created to be almost indestructible. They don’t break down easily or simply go away. Once in the environment, they accumulate over time. People can ingest or inhale them, and exposure has been linked to liver and kidney damage, fertility issues, cancer and other diseases. The EPA warned even low levels of exposure can be dangerous, setting strict near-zero limits for some PFAS in drinking water.

It's still unclear, though, how exactly these long-lived chemicals journey through the environment.

Quinete, who heads the Emerging Contaminants of Concern lab in FIU’s Institute of Environment, has been trying to piece this picture together.

Her research group is among the first to extensively track the prevalence of the persistent pollutants across South Florida. They’ve detected PFAS in drinking water and surface water including Biscayne Bay. And, subsequently, also found PFAS in animals that live in those areas, including oysters and economically important recreational fish and lobsters. Rain was the natural next place for the team to look.

PFAS can infiltrate the atmosphere by either evaporation or getting absorbed into microscopic particles and dust. Wind and shifting air currents shuttle them along. Eventually, it rains. As each drop falls to earth, it brings along some of the pollutants. The cycle begins and ends and begins again.

This played out in the team’s data.

Between October 2021 and November 2022, the most frequently detected and abundant PFAS in Miami’s rainwater, in 74% of samples, were PFCAs — commonly used in non-stick and stain-resistant products, food packaging and firefighting foams. The researchers previously detected high levels of these compounds in nearby surface waters, a sign they’re coming from local sources.

However, a noticeable shift occurred at certain times of year. PFAS concentrations suddenly skyrocketed during the dry season (October through May), coinciding with Northeastern air masses moving into Miami. More emerging PFAS also made an appearance including those typically found in North Carolina and other states, where facilities produce goods made with these particular chemicals.

“The season variations were interesting to us,” said Maria Guerra de Navarro, a graduate student in Quinete’s lab who helped lead the study. “We know there are northern states with manufacturing that matches back to the PFAS we saw, so it’s likely that’s where they are coming from.”

Here’s what the researchers suspect is happening: Drier air in northern currents creates perfect conditions for more PFAS-laden dust and particles to spread around. Rain “washing out” those pollutants from the air could account for higher contaminant concentrations. Guerra de Navarro is currently examining this kind of dry deposition, measuring how many PFAS can be packed into particles smaller than 10 microns — seven times smaller than the strand of a human hair (70 microns).

As with their past research, the team hopes the data can help guide future solutions and regulations for controlling and reducing PFAS.

“This is all about creating awareness that this is all one world,” says Guerra de Navarro. “What’s happens in one area can impact here, there, everywhere. We have to be thinking about how to prevent these chemicals from going all over the world.”