Carla Ng watches a student pipette in the lab
Earth Month

PFAS, the ‘forever chemicals,’ explained by Pitt engineer Carla Ng

  • Innovation and Research
  • Sustainability
  • Swanson School of Engineering

“Forever chemicals” have made the news recently, with new EPA rules limiting the amount of some types that can be in drinking water.

As Earth Month 2024 winds down, we asked leading forever chemical expert Carla Ng, an associate professor of civil and environmental engineering at the University of Pittsburgh Swanson School of Engineering, to explain what these chemicals are, where they’re found and what’s being done to limit their impact.  

What exactly are forever chemicals?

When scientists created a chemical compound capable of repelling both water and oil in the 1940s, they believed it was a revolution in materials sciences. They weren’t wrong.

That class of chemical compounds, called per- and polyfluorinated alkyl substances (PFAS), were quickly used to create useful domestic products like Teflon and dental floss, along with industrial agents like firefighting foam. They even found use in parts of the Manhattan Project.

Decades later, PFAS are still around. Because of their impressive surface density, these “forever chemicals” don’t naturally break down in either the human body or nature, causing health concerns like cancer, thyroid disease and reproductive impairment.

Ng has devoted much of her career to studying common sources of PFAS contamination, and collaborating to create road maps that reduce nonessential uses of PFAS, stop human and environmental exposure from getting worse and more equitably distribute the associated costs.

[Watch: Carla Ng on how forever chemicals became a “forever headache”]

Where are they found?

Pretty much everywhere.

Ng explained that while society is more aware of the risks PFAS pose than we were in the 1940s, the chemicals are still being widely used today for specialized firefighting foams, personal care products and food packaging, just to name a few applications.

“It’s hard to escape them,” Ng said.

The Environmental Protection Agency (EPA) reports that most people in the United States have been exposed to PFAS in some capacity. Exposure happens when touching, eating, drinking or breathing in materials containing PFAS, commonly from drinking water, waste sites, consumer products like nonstick repellants or fire extinguishing foam.

Ng recommends using the Environmental Working Group’s interactive map, which tracks PFAS contamination throughout the United States. She notes that states with higher levels typically have the most research completed behind them.

“Scientists still do not know how much PFAS have been produced globally, which means major ‘hotspots’ of PFAS contamination are probably being missed,” Ng said.

How do scientists test for contamination in drinking water?

Until this month, there was no national standard for PFAS maximum contaminant level, so individual states set their own. Pennsylvania, for example, set its maximum level for PFOA and PFOS — both fall under the PFAS umbrella — at 14 parts per trillion for PFOA and 18 parts per trillion for PFOS on January 14, 2023.

The EPA has its own approved method for testing drinking water and utilizes a certified lab. Ng’s lab used a method called 1633 — which is still in development by the EPA — when trying to understand how much contamination occurred when a small Pittsburgh community faced its own ecological disaster. While it requires double the volume of water compared to the EPA method, it’s capable of detecting a wide range of PFAS compounds.

Can they be eradicated?

There was a time before PFAS was used for everything and found everywhere. We won’t be going back to that anytime soon.

“Even if we are able to immediately stop the use of these PFAS chemicals, the problem lies with the forever chemical properties that they have,” Ng said. “It’s going to be a really long time before the environment is clean again.”

One question that sits between us and a future with fewer forever chemicals is whether PFAS is necessary. Ng and other researchers have been trying to determine if there are ethical, non-harmful alternatives that will allow us to stop using PFAS in some applications. It’s possible to find a suitable replacement for nonstick pans and dental floss, but what about green technology, safety suits or medical devices?

“The importance is that this shouldn’t be permanent, and we need to have innovation to drive the creation of replacements of these compounds,” Ng said.

There’s still a gray area when it comes to disposing household items that contain these chemicals as they just typically end up in landfills, creating a cyclical problem as regulations of PFAS are still coming to light.

At home, at least, there are ways to limit one’s risk of contamination. Both granular activated carbon and reverse osmosis filters can reduce PFAS levels in drinking water.


— Kat Procyk, photography by Johnathan Wright