US environmental regulators can now block new chemicals if they pose a 'significant new use' risk

The US environmental regulators can now require companies to get approval before using certain chemicals in new ways. This means companies must notify the regulators 90 days in advance if they plan a new use for a chemical that has been flagged.

For decades, new chemicals were often approved with broad uses, and regulators could only intervene after problems emerged. This rule means the regulators can now define what constitutes a 'significant new use' for a chemical and block it before it starts. This shifts the burden of proof to manufacturers for certain substances, requiring them to demonstrate safety for new applications.