A new study by scientists at Duke University and North Carolina State University found that while using either 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. Fortunately, filtering PFAS is easy with the right type of filter. The National Sanitation Foundation maintains a list of certified filters and the contaminants that must be removed from the water. Some California water utilities have closed contaminated wells, placed them in a state of “emergency only”, or processed their water through treatment plants.
Unlike Michigan, which has committed to testing all of its public water providers, California has not said whether it will do the same, let alone focus its attention on private drinking water wells. California has about 3,000 water providers, some of which purchase water from wholesalers that operate their own groundwater wells. Typically, PFAS filtered with activated carbon end up in landfills after disposal, while reverse osmosis systems generally concentrate PFAS in the untreated portion of the water leaving the system, reintroducing contaminants to the environment outside the home. These filters are considered to be the most effective, but they produce large quantities of wastewater, approximately three times more water than they treat.
Nearly 300 drinking wells and other water sources in California have been found to have traces of man-made chemicals related to cancer. If people live in states that don't publish their known contamination sites, or if they're in private or well water, Stapleton says they can pay to have their water tested in a private laboratory, or call their local water municipality and ask if they test for the chemical. As the prevalence of PFAS increases in public drinking water sources, treatment facilities must begin to specifically filter the chemical class to improve their contaminant levels. Although state-mandated PFAS testing is just beginning in California, there are already examples of water districts spending money to build new treatment facilities or buying clean water from other locations to replace wells that were closed.
So far, the California State Water Resources Control Board has tested about 600 water sources, a small fraction of the entire system, and it's unclear how quickly the state will move to require more. On March 17, the National Sanitation Foundation (NSF) International certified this filter as efficient and safe for drinking water treatment and approved its use for commercial purposes. If you live in a community where drinking water is already being tested, such as Wausau, Yang said there's probably no need to retest your own water at home. Pitcher filters, refrigerator- and faucet-mounted filters, and large whole-house treatment systems typically use this technology, but keep in mind that not all filters are certified to eliminate PFAS.
The good news for people living in affected areas is that existing domestic filtration technologies, specifically reverse osmosis and granular activated carbon systems, can filter some, but not all, of the PFAS chemicals from the water. An affordable, high-quality tap water filter that uses activated carbon such as TAPP 2 will reduce PFAS by 95% or more.