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How to reduce PFAS in your drinking water, according to experts

Mar. 07, 2024
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In the next three years, drinking water in the United States may be a bit safer from potentially toxic chemicals that have been detected in the blood of 98% of Americans.

Perfluoroalkyl and polyfluoroalkyl substances or PFAS are a family of thousands of man-made chemicals that do not break down easily in the environment. A number of PFAS have been linked to serious health problems, including cancer, fertility issues, high cholesterol, hormone disruption, liver damage, obesity and thyroid disease.

The US Environmental Protection Agency proposed on Tuesday stringent new limits on levels of six PFAS chemicals in public water systems. Under the proposed rule, public systems that provide water to at least 15 service connections or 25 people will have three years to implement testing procedures, begin notifying the public about PFAS levels, and reduce levels if above the new standard, the EPA said.

Two of the most well-studied and potentially toxic chemicals, PFOA and PFOS, cannot exceed 4 parts per trillion in drinking water, compared with a previous health advisory of 70 parts per trillion, the EPA said.

Another four chemicals — PFNA, PFHxS, PFBS and GenX — will be subject to a hazard index calculation to determine whether the levels of these PFAS pose a potential risk. The calculation is “a tool the EPA uses to address the cumulative risks from all four of those chemicals,” said Melanie Benesh, vice president of government affairs for the Environmental Working Group, a consumer organization that monitors exposure to PFAS and other chemicals.

“The EPA action is a really important and historic step forward,” Benesh said. “While the proposed regulations only address a few PFAS, they are important marker chemicals. I think requiring water systems to test and treat for these six will actually do a lot to address other PFAS that are in the water as well.”

Testing your water

For people who are concerned about PFAS exposure, three years or so is a long time. What can consumers do now to limit the levels of PFAS in their drinking water?

First, look up levels of PFAS in your local public water system, suggested David Andrews, a senior scientist at the Environmental Working Group. The advocacy nonprofit has created a national tap water database searchable by zip code that lists PFAS and other concerning chemicals, as well as a national map that illustrates where PFAS has been detected in the US.

However, not all water utilities currently test for pollutants, and many rural residents rely on wells for water. Anyone who wants to personally test their water can purchase a test online or from a certified lab, Andrews said.

“The most important thing is to ensure the testing method can detect down to at least four parts per trillion or lower of PFAS,” he said. “There are a large number of labs across the country certified to test to that level, so there are a lot of options available.”

Filtering your water

If levels are concerning, consumers can purchase a water filter for their tap. NSF, formerly the National Sanitation Foundation, has a list of recommended filters.

“The water filters that are most effective for PFAS are reverse osmosis filters, which are more expensive, about in the $200 range,” Andrews said. Reverse osmosis filters can remove a wide range of contaminants, including dissolved solids, by forcing water through various filters.

“Granular activated carbon filters are more common and less expensive but not quite as effective or consistent for PFAS,” he said, “although they too can remove a large number of other contaminants.”

Installing a reverse osmosis filter for your tap is an effective way to remove potentially toxic chemicals from your drinking water.

Prostock-studio/Adobe Stock

Reverse osmosis systems use both carbon-based filters and reverse osmosis membranes, Andrews explained. Water passes through the carbon filter before entering the membrane.

“The important part is that you have to keep changing those filters,” he said. “If you don’t change that filter, and it becomes saturated, the levels of PFAS in the filtered water can actually be above the levels in the tap water.”

Carbon filters are typically replaced every six months, “while the reverse osmosis filter is replaced on a five-year time frame,” he added. “The cost is relatively comparable over their lifetime.”

Another positive: Many of the filters that work for PFAS also filter other contaminants in water, Andrews said.

Challenges of PFAS removal

Drinking water is not the only way PFAS enters the bloodstream. Thousands of varieties of PFAS are used in many of the products we purchase, including nonstick cookware, infection-resistant surgical gowns and drapes, mobile phones, semiconductors, commercial aircraft, and low-emissions vehicles.

The chemicals are also used to make carpeting, clothing, furniture, and food packaging resistant to stains, water and grease damage. Once treated, the report said, textiles emit PFAS over the course of their lifetimes, escaping into the air and groundwater in homes and communities.

Made from a chain of linked carbon and fluorine atoms that do not readily degrade in the environment, PFAS are known as “forever chemicals.” Due to their long half life in the human body, it can take some PFAS years to completely leave the body, according to a 2022 report by the prestigious National Academies of Sciences, Engineering, and Medicine.

“Some of these chemicals have half-lives in the range of five years,” National Academies committee member Jane Hoppin, an environmental epidemiologist and director of the Center for Human Health and the Environment at North Carolina State University in Raleigh, told CNN previously.

“Let’s say you have 10 nanograms of PFAS in your body right now. Even with no additional exposure, five years from now you would still have 5 nanograms.

“Five years later, you would have 2.5 and then five years after that, you’d have one 1.25 nanograms,” she continued. “It would be about 25 years before all the PFAS leave your body.”

The 2022 National Academies report set “nanogram” levels of concern and encouraged clinicians to conduct blood tests on patients who are worried about exposure or who are at high risk. (A nanogram is equivalent to one-billionth of a gram.)

People in “vulnerable life stages” — such as during fetal development in pregnancy, early childhood and old age — are at high risk, the report said. So are firefighters, workers in fluorochemical manufacturing plants, and those who live near commercial airports, military bases, landfills, incinerators, wastewater treatment plants and farms where contaminated sewage sludge is used.

The PFAS-REACH (Research, Education, and Action for Community Health) project, funded by the National Institute of Environmental Health Sciences, gives the following advice on how to avoid PFAS at home and in products:

  • Stay away from stain-resistant carpets and upholstery, and don’t use waterproofing sprays.

  • Look for the ingredient polytetrafluoroethylene, or PTFE, or other “fluoro” ingredients on product labels.

  • Avoid nonstick cookware. Instead use cast-iron, stainless steel, glass or enamel products.

  • Boycott takeout containers and other food packaging. Instead cook at home and eat more fresh foods.

  • Don’t eat microwave popcorn or greasy foods wrapped in paper.

  • Choose uncoated nylon or silk dental floss or one that is coated in natural wax.

DURHAM, N.C. – The water filter on your refrigerator door, the pitcher-style filter you keep inside the fridge and the whole-house filtration system you installed last year may function differently and have vastly different price tags, but they have one thing in common.

They may not remove all of the drinking water contaminants you’re most concerned about.

A new study by scientists at Duke University and North Carolina State University finds that – while using any filter is better than using none – many household filters are only partially effective at removing toxic perfluoroalkyl substances, commonly known as PFAS, from drinking water. A few, if not properly maintained, can even make the situation worse.

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

“All of the under-sink reverse osmosis and two-stage filters achieved near-complete removal of the PFAS chemicals we were testing for,” Stapleton said. “In contrast, the effectiveness of activated-carbon filters used in many pitcher, countertop, refrigerator and faucet-mounted styles was inconsistent and unpredictable. The whole-house systems were also widely variable and in some cases actually increased PFAS levels in the water.”

“Home filters are really only a stopgap,” said Detlef Knappe, the S. James Ellen Distinguished Professor of Civil, Construction and Environmental Engineering at NC State, whose lab teamed with Stapleton’s to conduct the study. “The real goal should be control of PFAS contaminants at their source.”

PFAS have come under scrutiny in recent years due to their potential health impacts and widespread presence in the environment, especially drinking water. Exposure to the chemicals, used widely in fire-fighting foams and stain- and water-repellants, is associated with various cancers, low birth weight in babies, thyroid disease, impaired immune function and other health disorders. Mothers and young children may be most vulnerable to the chemicals, which can affect reproductive and developmental health.

Some scientists call PFAS “forever chemicals” because they persist in the environment indefinitely and accumulate in the human body. They are now nearly ubiquitous in human blood serum samples, Stapleton noted.

The researchers published their peer-reviewed findings Feb. 5 in Environmental Science & Technology Letters. It’s the first study to examine the PFAS-removal efficiencies of point-of-use filters in a residential setting.

They analyzed filtered water samples from homes in Chatham, Orange, Durham and Wake counties in central North Carolina and New Hanover and Brunswick counties in southeastern N.C. Samples were tested for a suite of PFAS contaminants, including three perfluoroalkal sulfonic acids (PFSAs), seven perfluoroalkyl carboxylic acids (PFCAs) and six per- and poly-fluoroalkyl ether acids (PFEAs). GenX, which has been found in high levels in water in the Wilmington area of southeastern N.C., was among the PFEAs for which they tested.

Key takeaways include:

  • Reverse osmosis filters and two-stage filters reduced PFAS levels, including GenX, by 94% or more in water, though the small number of two-stage filters tested necessitates further testing to determine why they performed so well.
  • Activated-carbon filters removed 73% of PFAS contaminants, on average, but results varied greatly. In some cases, the chemicals were completely removed; in other cases they were not reduced at all. Researchers saw no clear trends between removal efficiency and filter brand, age or source water chemical levels. Changing out filters regularly is probably a very good idea, nonetheless, researchers said.
  • The PFAS-removal efficiency of whole-house systems using activated carbon filters varied widely. In four of the six systems tested, PFSA and PFCA levels actually increased after filtration. Because the systems remove disinfectants used in city water treatment, they can also leave home pipes susceptible to bacterial growth.

“The under-sink reverse osmosis filter is the most efficient system for removing both the PFAS contaminants prevalent in central N.C. and the PFEAs, including GenX, found in Wilmington,” Knappe said. “Unfortunately, they also cost much more than other point-of-use filters. This raises concerns about environmental justice, since PFAS pollution affects more households that struggle financially than those that do not struggle.”

Nick Herkert, a postdoctoral associate in Stapleton’s lab, was lead author on the study. John Merrill of NC State and Cara Peters, David Bollinger, Sharon Zhang, Kate Hoffman and Lee Ferguson of Duke were co-authors. Funding came from the N.C. Policy Collaboratory through the N.C. PFAS Testing Network and from the Wallace Genetic Foundation.

CITATION: “Assessing the Effectiveness of Point-of-Use Residential Drinking Water Filters for Perfluoroalkyl Substances (PFAS),” Nicholas J. Herkert, John Merrill, Cara Peters, David Bollinger, Sharon Zhang, Detlef R.U. Knappe, Kate Hoffman, P. Lee Ferguson and Heather M. Stapleton; Feb. 5, 2019, Environmental Science & Technology Letters.

DOI: 10.1021/acs.estlett.0c00004

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