Does Filtering Water Remove PFAS? [Learn More]

Water filtration is only partially effective at removing hazardous PFA chemicals.

According to a recent study by researchers at Duke University and North Carolina State University, many household filters are only partially efficient at removing harmful perfluoroalkyl compounds, or PFAS, from drinking water, even though using any filter is preferable to using none at all. A few, if not kept up with, can further exacerbate the problem.

Heather Stapleton, the Dan and Bunny Gabel Associate Professor of Environmental Health at Duke’s Nicholas School of the Environment said, “We examined 76 point-of-use filters and 13 point-of-entry or whole-house systems and found their performance varied substantially.

The PFAS compounds we were testing for were nearly completely removed by all of the under-sink reverse osmosis and two-stage filters, according to Stapleton. Contrarily, the performance of activated-carbon filters, which are commonly used in pitchers, countertops, refrigerators, and faucet-mounted models, was erratic and unpredictable. The whole-house systems likewise varied greatly, and occasionally they even made the water’s PFAS levels higher.

Home filters are really just a band-aid, according to Detlef Knappe, a professor of civil, construction, and environmental engineering at NC State whose lab collaborated with Stapleton’s on the research. “Control of PFAS pollutants at their source should be the real objective.”

ALSO SEE: Does Reverse Osmosis Remove PFAS?

Due to their potential health effects and pervasive presence in the environment, particularly drinking water, PFAS has drawn attention in recent years. The chemicals, which are commonly used in firefighting foams and stain- and water-repellants, are linked to a number of malignancies, low birth weight in infants, thyroid disease, weakened immune systems, and other illnesses.

The toxins, which can harm reproductive and developmental health, may be especially dangerous to mothers and young children.

Because PFAS linger in the environment forever and build up in the body, some scientists refer to them as “forever chemicals.” According to Stapleton, they are now almost always present in tests of human blood serum.

Environmental Science & Technology Letters, a peer-reviewed journal, published the researchers’ results on February 5. It is the first study to look at point-of-use filters’ abilities to remove PFAS in a residential setting.

In Chatham, Orange, Durham, and Wake counties in the center of North Carolina, as well as New Hanover and Brunswick counties in the southeast, they examined filtered water samples taken from residences.

Three perfluoroalkal sulfonic acids (PFSAs), seven perfluoroalkyl carboxylic acids (PFCAs), and six per- and poly-fluoroalkyl ether acids were among the PFAS pollutants that were evaluated in the samples (PFEAs). One of the PFEAs they tested for was GenX, which has been discovered at significant concentrations in water in the Wilmington region of southeast North Carolina.

Important lessons include:

  • Although the small number of two-stage filters examined makes it necessary for additional testing to discover why they performed so well, reverse osmosis filters and two-stage filters reduced PFAS levels, especially GenX, in water by 94% or more.
  • On average, PFAS pollutants were removed by activated-carbon filters at a rate of 73%, but results varied substantially. Chemicals were partially or totally eliminated in some instances while they were completely decreased in others. Researchers found no discernible correlations between filter brand, age, or source water chemical levels and removal effectiveness. However, researchers stated it is probably a very good idea to replace filters frequently.
  • The effectiveness of whole-house systems using activated carbon filters to remove PFAS varied greatly. After filtration, PFSA and PFCA levels actually rose in four out of the six systems that were put to the test. The systems can also expose house pipes to bacterial growth since they eliminate disinfectants used in city water treatment.

The most effective system for eliminating both the PFEAs, including GenX, found in Wilmington and the PFAS pollutants common in central North Carolina is the under-sink reverse osmosis filter, according to Knappe. Sadly, they are also significantly more expensive than other point-of-use filters.

Given that PFAS pollution impacts households that struggle financially more than those that do not, this raises questions regarding environmental justice.

The study’s lead author was Nick Herkert, a postdoctoral associate in Stapleton’s group. The writers included Cara Peters, David Bollinger, Sharon Zhang, Kate Hoffman, Lee Ferguson, and John Merrill from NC State and Duke. The Wallace Genetic Foundation and N.C. Policy Collaboratory provided funding via the N.C. PFAS Testing Network.

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