Do Whole House Water Filters Remove Pfas? [Learn More]

Yes! a lot of whole household water filters are only partially effective at removing toxic perfluoroalkyl substances, commonly known as PFAS, from drinking water.

Some scientists refer to PFAS as “forever chemicals” because they last forever in the environment and build up in the human body. Stapleton said that they are now almost always found in samples of human blood serum.

A new study by scientists at Duke University and North Carolina State University shows that, while using any filter is better than not using any, many household filters are only partially effective at removing toxic perfluoroalkyl substances, or PFAS, from drinking water. Some, if not taken care of properly, can even make things worse.

Heather Stapleton, the Dan and Bunny Gabel Associate Professor of Environmental Health at Duke’s Nicholas School of the Environment said, “We tested 76 point-of-use filters and 13 point-of-entry or whole-house systems and found that their effectiveness was all over the place.”

Stapleton said that all of the under-sink reverse osmosis and two-stage filters got almost all of the PFAS chemicals we were looking for out of the water. “On the other hand, activated-carbon filters used in many pitcher, countertop, refrigerator, and faucet-mounted models didn’t work as well as they should have. The whole-house systems were also very different, and in some cases, they actually made the water contain more PFAS.

“Home filters are really just a stopgap,” said Detlef Knappe, the S. James Ellen Distinguished Professor of Civil, Construction, and Environmental Engineering at NC State, whose lab worked with Stapleton’s to do the study. “The real goal should be to stop PFAS pollutants where they come from.”

ALSO SEE: Do any Water Filters Remove PFAS

Environmental Science & Technology Letters came out on February 5 with the researchers’ results, which had been reviewed by other scientists. It is the first study to look at how well point-of-use filters remove PFAS in a residential setting.

They looked at filtered water samples from homes in Chatham, Orange, Durham, and Wake counties in central North Carolina and in New Hanover and Brunswick counties in southeastern North Carolina. Three perfluoroalkal sulfonic acids (PFSAs), seven perfluoroalkyl carboxylic acids (PFCAs), and six per- and poly-fluoroalkyl ether acids were looked for in the samples (PFEAs). One of the PFEAs they tested for was GenX, which has been found in high levels in the water in the Wilmington area of southeastern North Carolina.

Some important points are:

  • Reverse osmosis filters and two-stage filters cut the amount of PFAS, including GenX, in water by 94% or more. Since only a few two-stage filters were tested, more research is needed to figure out why they worked so well.
  • On average, activated-carbon filters got rid of 73% of PFAS contaminants, but the results were very different. In some cases, the chemicals were taken out completely, and in other cases, they were not reduced at all. Researchers didn’t find any clear links between how well a filter removed chemicals and the brand, age, or chemical levels of the source water. Researchers said, though, that it’s probably a good idea to change filters often.

There were a lot of differences in how well-activated carbon filters removed PFAS from whole-house systems. After filtration, the levels of PFSA and PFCA went up in four of the six systems that were tested. Because the systems get rid of the disinfectants used to treat city water, bacteria can grow in the pipes of homes.

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