There’s increasing concern over a chemical spill into the Farmington River that happened earlier this month. An accident June 9 at Bradley Airport released 50,000 gallons of firefighting foam containing chemicals known as PFAS -- and a substantial amount of it made its way from the sewer system into the waterway. In the days since, it’s become evident that it’s going to be very hard to contain and remove the chemicals from the spill.

New Hampshire Public Radio’s environment reporter Annie Ropeik has covered the issue of PFAS pollution around the region for several years. She joined Connecticut Public Radio's Morning Edition to tell us more about these chemicals.

What are they?

It's a really broad class of thousands of industrial chemicals that were used for decades in all kinds of products -- think Teflon, Gore-Tex, stain-resistant carpets, greaseproof packaging for food -- really, I think of it as anything that resists something -- so water, heat, or grease. In the case of firefighting foams, they are flame retardant.

Even though PFAS chemical production in the U.S. has ramped down in the past couple of decades, places like airports and military bases will have vast stores of these foams in their sprinkler systems.

How large an environmental risk does a spill like this pose?

It's potentially a very big environmental risk. These chemicals are really tricky because they latch on to bodies and to the environment really easily, and they're really hard to get out. And they also can have potential health risks in really, really, really small amounts. So a spill like this, depending on how much of those chemicals did get into your groundwater system, into the drinking water, into the water lines -- that water could make its way to people's taps, into people's private wells and into municipals wells. And it may be so dispersed that it winds up there at really low level.

But firefighting foam contains really high amounts of these chemicals so it could be quite concentrated in certain areas. It's hard to find it, it's hard to test for it, because ths is a fairly new area of environmental study. Also water treatment facilities don't tend to have treatment installed to get rid of these chemicals because there's very little regulation around them, and that's only just starting to develop.

What kinds of health risks?

The science around that is still evolving too, but it's pretty clear that these chemicals can cause, or have been linked to kidney disease, liver problems, high cholesterol, as well as developmental and immune disruptions, reproductive issues, and there's growing research to suggest that they could be linked to certain types of cancer as well.

How are affected communities thinking about regulation and clean-up?

Regulation is really difficult, because there are thousands of these chemicals, and we only have good science around a handful of them, maybe a dozen or fewer. Treatment technologies also are still evolving to test for the really low levels of these that have been linked to health problems. Some advocates want them regulated as a class, not one-by-one. But right now, one-by-one is how the federal and state regulation is proceeding.

States like New Hampshire where I am, have proposed, or are about to propose drinking water standards for these chemicals. There is no federal drinking water standard, which means no treatment is required of public water systems. And then communities are also really struggling with the cost of clean-up when these chemicals are found.

It's a problem without an owner because these chemicals came from companies like 3M and Dupont that were made decades ago and sold to firefighting foam companies. Who's liable? Who actually put it in the water? These are all huge questions that people have to solve before the funding can come through to actually help fix the problems, which can be really expensive.

This interview has been lightly edited from its original broadcast form.