Should you worry if chemicals were detected near you?

There are some important caveats to this data.

First, there’s no way to know if you’re drinking water from a contaminated well without calling your water provider. State regulators have provided a contact number for most of the tested wells, which you can find in the info box on the map.

Second, even if you drink from a contaminated well, it’s possible that your water is mixed with multiple water sources before it reaches your tap. The water is tested at the source, and in some cases the water is treated before it’s sent to consumers. There’s no way to know if your water is mixed or treated without calling your water utility.

Why weren’t the wells near me tested?

State regulators mandated testing at roughly 600 wells deemed at high risk for contamination. Those included water sources close to airports or landfills and sites that previously tested positive. While more wells will be tested in the future, many thousands of wells at a lower risk for contamination have not been tested.

What can you tell me about these chemicals?

Scientists have called them “forever chemicals” because they persist indefinitely and accumulate in the human body. The chemicals were developed in the 1940s and used in countless household products, from Teflon cookware and Scotchgard to waterproof clothing and food packaging.

There is no agreed-upon safe level of PFOS and PFOA. The Environmental Protection Agency has classified the chemicals as an “emerging contaminant” and has delayed setting a national standard for limiting the levels in drinking water. In 2016, the agency issued a nonbinding health advisory recommending that water utilities notify the public if levels of the chemicals reached a combined 70 parts per trillion.

Read more about the chemicals in Monday’s Times story.