The EPA just made the safe limit for two harmful chemicals in drinking water way stricter—dropping from 70 to just 4 tiny parts per trillion—but some scientists are saying that big drop isn't really backed by solid science.

The EPA says super tiny amounts of a chemical called PFOA in water could be harmful, but our current tools can't reliably detect levels that low — we can only measure down to a level 1,000 times higher.

The EPA just made its safety limits for two harmful chemicals in drinking water way stricter — now saying even tiny amounts of PFOA and PFOS can be risky, much lower than before and compared to other countries.

The EPA's super strict safety levels for two chemicals in drinking water are way lower than other countries' rules — like thousands of times lower — so some people question whether the science behind them really adds up.

The EPA changed how it calculates safe levels of PFOA and PFOS in drinking water, using new science methods, which led to much stricter safety limits—from 70 to nearly zero in some cases.

The EPA's new rules on PFAS in drinking water will probably hold up in court because judges usually trust government experts, even if scientists don't all agree.