GEOFF BENNETT: A recent government study estimates that nearly half of America's tap water could contain toxic forever chemicals known as PFAS.

As Stephanie Sy reports, there are thousands of these chemicals, and exposure to them can lead to serious health effects.

STEPHANIE SY: Amna, last month, the U.S. Geological Survey tested the nation's drinking water and found at least 45 percent of samples had one or more forever chemicals.

The study also found contamination centered in urban areas and near industrial sites.

These chemicals have been used in many everyday items since the 1940s, from nonstick cookware to cosmetics to rain jackets.

PFAS are also widely used as a firefighting chemical.

3M, a PFAS manufacturer, recently proposed a more-than-$10 billion settlement to address claims by hundreds of cities that want the company held liable for contaminating public water supplies.

But litigation continues, and 3M will continue to make the chemicals until 2025.

For more on the possible harms of PFAS and what can be done, I'm joined by Jamie DeWitt, professor of pharmacology and toxicology at East Carolina University.

Professor DeWitt, thank you for joining the "NewsHour."

There have been studies showing that all of us have some level of PFAS in our bodies.

How much should we worry about this?

JAMIE DEWITT, East Carolina University: Well, PFAS are a very large group of chemicals.

There's about 14,000 individual chemicals.

And they're associated with many of the chronic diseases that take people's lives today.

So, people should be concerned.

But they should also be concerned about all of the different chemicals that are in the environment that are leading to chronic diseases that we experience in our lives today.

STEPHANIE SY: Well, that's just it.

There are so many different chemicals, we sort of all assume, in the air, in the water.

What makes PFAS particularly insidious and toxic?

And you said that PFAS have been linked to certain cancers and disease.

At what levels of exposure?

Do we know that?

JAMIE DEWITT: So, we know that exposure to PFAS are particularly problematic because they're very persistent.

That means that they last for a very long time in the environment, maybe longer than any other chemical synthesized to date.

They also tend to last for a long time inside of our bodies, giving them the opportunity to interact with different parts of our bodies to lead to those diseases.

And they have been linked to diseases such as kidney cancer and testicular cancer and a host of other diseases.

In the world of toxicology, we call them multisystem toxicants because they can affect many different parts of the body.

STEPHANIE SY: And from what I understand, at least so far, the research says it has to be pretty high concentration of PFAS for there to be this linkage.

Do we know what communities and areas of the country are at higher risk of exposure to PFAS?

JAMIE DEWITT: We do know that people who live in areas where there is known contamination to their drinking water and people who work for PFAS have higher concentrations of them in their bodies.

In 2022, the National Academies came out with a report for clinicians, health care providers who might be treating people who are exposed to PFAS, and they had some specific recommendations for elevated standards of care that health care providers could give to patients who had concentrations greater than 20 nanograms per mil of seven different PFAS in their blood.

Twenty nanograms per milliliter is a very small amount.

STEPHANIE SY: The Biden administration's EPA, as you know, has taken several actions to highlight the dangers of PFAS.

In fact, they have just announced $5 billion in grant funding to states that want to address PFAS in the environment.

How much can that help?

And should some of these chemicals be banned outright?

JAMIE DEWITT: Well, efforts to limit some of the PFAS that are being proposed by the Biden administration are really good step forward.

Even though only six PFAS are being recommended for regulatory action, if the technologies in place to filter out those six PFAS are implemented, then those technologies also will work to filter out a huge number of other PFAS.

So it is a good step forward.

There are some efforts at levels of individual states and in different countries in the European Union, for example, to ban or phase out what are considered to be nonessential uses of PFAS.

STEPHANIE SY: Is there any at-home technology that the average person can use if they want to reduce their PFAS exposure, especially in their drinking water?

I mean, can you use water filters and things like that?

JAMIE DEWITT: Yes, that's a really good question.

And that's a question that a lot of different scientists studying PFAS removal and remediation get asked.

There are some filters that you could buy at a grocery store, for example, that have carbon filters in them.

Those do a decent job of filtering out some PFAS, but you have to be very good about changing out your filter.

And for those who can afford it, reverse osmosis, such as under the sink, or whole-home reverse osmosis can also be very good at filtering out many different PFAS.

But those are often out of reach for many individual homeowners because of their price.

STEPHANIE SY: Jamie DeWitt, professor of pharmacology and toxicology at East Carolina University, thanks so much for joining us with your expertise.

JAMIE DEWITT: Thank you.