Clean, safe drinking water is a luxury that many people in the United States take for granted. But your tap water may not be as safe as you think.

Nearly half of US tap water, from both public utilities and private wells, contains so-called forever chemicals—commonly known as per- and polyfluoroalkyl substances, or PFAS—according to a US Geological Survey study released this month.

The risks of PFAS exposure are well documented and have been linked with a host of health risks, including cancer, obesity, and weakened immune function.

If you’re concerned about PFAS in your tap water, you can take several practical steps.

First, determine whether your water is in fact contaminated, and if so, to what degree.

Then, if necessary, invest in a water filter that significantly reduces PFAS.

Keep in mind that PFAS are ubiquitous in the environment. They’re present in numerous common household products. It’s almost impossible to avoid PFAS entirely. But you can limit your exposure.

That distinction is important. Because PFAS don’t break down, they can accumulate in soil, water, and living tissue. Thus, the health risks may build with repeated exposures over time. For more on limiting your risk, see our guide.

Figure out if your water contains […]