How many times a day do you drink water? Cook with it? Brush your teeth with it? Offer some to your children?

Safe drinking water is essential to your family’s health and well-being, so it’s troubling that drinking water supplies for at least 16 million American have been contaminated with nonstick chemicals known as PFCs or PFAS. The most infamous family member, PFOA, is a carcinogen that severely polluted the drinking water near a DuPont manufacturing plant in Parkersburg, W.Va.

Here’s some key information – and steps you can take to protect your family:

Drinking water contaminated with the toxic chemical PFOA is a more serious health threat than previously thought, according to a 2015 report by EWG. Two leading environmental health scientists have published research showing that exposure to PFOA is harmful at lower concentrations than those found in testing by the Environmental Protection Agency.

EWG’s Tap Water Database shows that between 2010 and 2015, PFOA has been detected in 220 public water systems in 27 states.

PFOA is a kind of perfluorinated chemical, or PFC. Nonstick, waterproof and grease-proof, coatings manufactured with PFCs have many commercial uses, such as clothing, cookware, carpets, furniture, food wrappers and more.

Toxic even in small doses, PFCs pass from mothers to their unborn babies through the umbilical cord. They have been linked to birth defects, pregnancy complications, kidney and testicular cancers, heart and thyroid disease, and other serious health conditions. Check out EWG’s Guide to Avoiding PFCs to learn more.

DuPont used to use PFOA to make Teflon coatings but eventually phased it out due to the health hazards. Although the chemical is no longer produced in the United States, the drinking water contamination and impacts on human health are ongoing. Today PFOA and its chemical cousins turn up in the blood of almost all Americans and in animals across the globe. Read the full report.

Other common hazardous drinking water contaminants include lead, perchlorate and the herbicide atrazine. Some of these toxic substances cannot be easily removed from drinking water – nor does the EPA always know how much must be removed for safety – but there are steps parents can take to improve the health of their families’ drinking water. Here’s where to start:

Investigate your water supply

According to EWG research, drinking water supplies for millions of American children and adults have higher amounts of 90 contaminants than scientists consider safe, even if the water gets a passing grade from the federal government. This number doesn’t account for the exposures of the more than 40 million people who drink water from private wells, which are not routinely monitored for contaminants.

Use EWG’s Tap Water Database to see if your water system reported testing for PFCs, and if PFOA or other PFCs were detected. If you don’t see your water provider in the database or want to learn more about tests, contact your provider directly to ask for more details on contaminant testing.

Use a water filter

Using a water filter is one of the fastest steps you can take to improve the quality of the water your family drinks. There are many options on the market, so consult EWG’s updated Water Filter Buying Guide to find the one that’s right for your needs and budget. If your utility’s water testing reveals a high level of a particular contaminant, consider buying a filter certified to reduce that specific one.

Drink from safer containers

Use reusable water bottles made from BPA-free plastic, stainless steel or glass. You’ll reduce waste and your family’s exposure to chemicals that can leach from plastics into the water. If you do choose plastic, keep it away from heat. And, outside of emergency situations, don’t use plastic containers to store water for prolonged periods.