Feb. 5 (UPI) -- Most municipal water systems don't filter out PFAS, a unique class of toxic chemicals, leaving citizens to remove the pollutants on their own. Unfortunately, new research suggests the majority of household water filters fail to entirely remove PFAS from water.
Per- and polyfluoroalkyl substances, or PFAS, are a class of synthetic compounds used in a variety of industrial processes and found in dozens of household items. They have been linked to a variety of health problems, including cancer and high cholesterol, and a report published last month found the toxins are accumulating in municipal drinking water all over the United States.
For the latest study, published Wednesday in the journal Environmental Science and Technology Letters, scientists wanted to find out how well household water filters protect drinkers from these harmful toxins.
"We tested 76 point-of-use filters and 13 point-of-entry or whole-house systems and found their effectiveness varied widely," lead researcher Heather Stapleton, professor of environmental health at Duke University, said in a news release.
"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."
Scientists tested water samples, before and after filtration, at homes in central and southeastern North Carolina. The tests screened for the presence of 16 different PFAS. There are 600 PFAS compounds currently being used by various industries, but the chemicals that are most prevalent in the environment -- and feature the most well-documented toxicity -- mostly originate from fire-fighting foams and stain- and water-repellents.
Because the chemical bonds in these unique human-made chemicals are so strong, they don't degrade. Natural processes don't break them down, which is why they're sometimes called "forever chemicals." They persist in the environment, and also in human blood.
"Certain ones stick to proteins in our blood," Rick Rediske, professor at the Annis Water Resources Institute in Michigan, told UPI last month. "DDT and pesticides go in to our fat. Lead goes into our bones. Mercury goes into muscle. Because PFAS are carried around in our blood and aren't discarded, they naturally concentrate over time. And they attach to the proteins that carry antibodies, cholesterol and hormones, that's why you get so many different health effects caused by these compounds."
The study carried out by Duke researchers showed the best ways to remove PFAS from drinking water at home is to use either reverse osmosis or two stage filters. The two techniques removed 94 percent of PFAS, while activated-carbon filters removed an average of 74 percent of PFAS.
"The under-sink reverse osmosis filter is the most efficient system," 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."