US environmental regulators can now block new uses of old chemicals

The US environmental regulators can now stop companies from using certain chemicals in new ways. Companies must tell the regulators 90 days before they start a new use, and they cannot proceed until the regulators approve it.

For years, companies could introduce new uses for existing chemicals without much oversight, as long as the chemical itself was already approved. This rule means the regulators can now review and potentially block those new uses. It shifts the burden of proof: companies must now show a new use is safe before they can start, rather than regulators having to prove it is unsafe after the fact.