Researchers have found some kinds of chemicals are harder to filter from water.
These compounds belong to a family called highly fluorinated chemicals. They’re used to make carpets, clothes and cookware stain and water repellant.
They’ve also been used in firefighting foam at military bases and airports. Those chemicals from firefighting foam have contaminated drinking water around the country, including drinking water wells near the former Wurtsmith Air Force Base near Oscoda.
Chris Higgins is an associate professor of civil and environmental engineering at the Colorado School of Mines.
“We used to think PCBs and DDT were going to be the most problematic chemicals because they are really long lived. These chemicals are much, much more long lived than things like PCBs,” he says.
Higgins is an author of a study out today in the journal Environmental Science & Technology. He and his team sampled a groundwater well near a military base where firefighting foam had been used. They found two chemicals that are commonly found in that foam, called PFOA and PFOS. And 28 other fluorinated chemicals.
Higgins says they ran tests in the lab to model how well a granular activated carbon filter would work on these chemicals (like the kind some water treatment plants use).
"These filters have the capacity to work for these other chemicals. You just have to replace the carbon much more frequently,” he says.
He says this matters because we don’t know a lot about many of these fluorinated chemicals. And it’s expensive to change out filters more often.
“I think the relevance for water treatment plants is we need to have a conversation about these other chemicals that might be present, and what is their importance? Do we care about them in terms of potential for toxicity and do we treat for them even though we do not have information on their toxicity?” he says.
The state of Michigan is providing reverse osmosis filters or bottled water coolers for people near Oscoda. They’re giving them to people with well water that’s affected by the plume from the former Air Force base.
Higgins says reverse osmosis filters are the best technology to remove these chemicals. But they're expensive.
Curbing future use
Arlene Blum is the executive director of the Green Science Policy Institute and a research associate in chemistry at the University of California-Berkeley.
She says there are about 3,000 highly fluorinated chemicals in existence, and we don't know much about most of them. The most studies have been done on PFOA and PFOS.
"We do know from human epidemiology studies that they are associated with a couple kinds of cancer, high cholesterol. For children, there’s an association with reduced immune response to vaccines. And a series of other human health effects," says Blum.
The EPA has set drinking water health advisories for PFOA and PFOS. They're guidelines, not regulations. Here's an excerpt from the EPA's page on PFOA and PFOS:
EPA’s health advisories are based on the best available peer-reviewed studies of the effects of PFOA and PFOS on laboratory animals (rats and mice) and were also informed by epidemiological studies of human populations that have been exposed to perfluoroalkyl substances (PFASs). These studies indicate that exposure to PFOA and PFOS over certain levels may result in adverse health effects, including developmental effects to fetuses during pregnancy or to breastfed infants (e.g., low birth weight, accelerated puberty, skeletal variations), cancer (e.g., testicular, kidney), liver effects (e.g., tissue damage), immune effects (e.g., antibody production and immunity), thyroid effects and other effects (e.g., cholesterol changes).
And when it comes to getting these chemicals out of the environment? That's the real challenge.
"That is the big problem. Since they don’t break down ever, they’re accumulating. And once we make them, they don’t go away," Blum says.
Blum says the best way to deal with highly fluorinated chemicals is to think carefully about their use in the first place.
"So, I think each use of these chemicals should be thought out. Do we really need highly fluorinated chemicals? Or could we use a safer alternative for this use?"