PHILADELPHIA (CBS) -- Water filters have become more popular following studies that show nearly half of the country's tap water could be contaminated with potentially toxic compounds. But which are the best water filters?
The Environmental Working Group tested 10 water pitchers and found some of the most well-known are "not" effective at fully filtering out PFAS.
The so-called forever chemicals -- used in products like nonstick cookware, stain-resistant carpets and cosmetics -- have been linked to an increased risk for a number of health problems, including certain cancers, high cholesterol and pregnancy complications.
"We've since discovered that all these PFAS are immune suppressants, so they suppress your immune system and that means any opportunistic disease, including some types of cancer, could take over," said Graham Peaslee, who is a biochemist.
PFAS have also been found in drinking water. A map from the Environmental Working Group shows contamination in the Phila region, as well as north into New York.
Now, there's growing interest in water filtration systems.
The Environmental Working Group testing showed three of the filters tested stood above the rest.
"They actually reduced PFAS down to non-detectable levels, which is really great," said Sydney Evans, with the Environmental Working Group.
In the study, pitchers from "Clearly Filtered" and "Zero Water" blocked 100% of PFAS tested. So did the standing travel Berkey filter system.
The Epic Pure pitcher was close, blocking 98% of PFAS.
However, for them to work properly, filters need to be changed, which can be costly.
The travel Berkey sells for $327, but the filter lasts eight years.
The other recommended pitchers have a lower up-front price but changing the filters can cost hundreds of dollars a year.
For a full year's use, Epic has the lowest price.
The Environmental Protection Agency (EPA) is now
The Environmental Working Group said until then, filters can help reduce your exposure. For more information on the testing of water filters, visit the EWG website.