The US Food and Drug Administration (FDA) is proposing to expand a controversial loophole to allow some of the world’s most toxic chemicals to be added directly to food without a safety review.

The “threshold of regulation” (TOR) exemption currently allows dangerous compounds to be used without review in food contact materials, such as packaging or processing equipment, if they are not carcinogenic, and are added at levels below 0.5 parts per billion (ppb).