A toxic chemical long used to make non-stick or water-repellent coatings may be more dangerous than believed — perhaps unsafe at any level, a leading environmental group warned Thursday.

Perfluorooctanoic acid, or PFOA, was used to make DuPont’s popular Teflon coating for decades. DuPont phased out its production after a 2006 settlement with federal regulators, who had linked it to birth defects and cancer in animals — and accused the company of failing to report those hazards for more than two decades.

In the meantime, PFOA spread worldwide. Traces of the compound have been found in the blood of nearly every American and in the bodies of polar bears in the Arctic and dolphins in India’s Ganges River. And now the Environmental Working Group (EWG), a nonprofit watchdog group, said the US Environmental Protection Agency’s (EPA) current safety standard for PFOA in drinking water is more than 1,000 times too high.

The current EPA standard for PFOA is 0.4 parts per billion — a concentration comparable to half a teaspoon of water in an Olympic-sized swimming pool. But Bill Walker, who wrote the new EWG report on the chemical, said the number should be 0.0003 parts per billion, or 1,333 times lower than the EPA’s figure and more than 300 times below the agency’s proposed permanent safe level.

The EWG figure suggests that PFOA may be in the same league as substances like asbestos or lead, “of which we know there is basically no safe level of exposure,” Walker told VICE News.

“We’re not prepared to go that absolute on this, but the truth of the matter is that it appears to be hazardous at very, very, very low levels of exposure,” he said. “In practicality, when you’re talking about these very, very tiny levels, there just may not be a safe level of exposure.”