U.S. manufacturers stopped using a hazardous chemical in pizza boxes and other food wrappers three years ago — but it may still be seeping into your takeout food.

That’s because foreign companies can still use perchlorate and perfluorocarboxylates (PFCs) – which can cause permanent brain damage in infants – in paper products that are imported into the United States.

On Thursday, a group of consumer and health groups filed a food additive petition with the Food and Drug Administration, asking that the agency pass regulations that would close this loophole and clearly ban the chemicals in food production. Perchlorate helps to reduce static and PFCs keep grease from soaking into food containers.

In 2011, the FDA identified the health hazards with the chemicals and asked three U.S. companies to voluntarily stop using them. The companies complied.

However, the New York-based Natural Resources Defense Council said it found that large manufacturers in China and India  that import their products into the United States may still use perchlorate and PFCs.

The petition cites more than a dozen scientific animal studies that show perchlorate interferes with the thyroid gland’s ability to make hormones from iodine.

These hormones are needed for brain development in fetuses and infants, the studies show. Other animal studies have shown that PFCs can damage male reproductive systems, including reducing testicular weight and causing testicular degeneration. It is unclear whether fertility is affected.

The NRDC is leading the petition effort and is joined by eight other consumer and health organizations, including the Breast Cancer Fund, the Center for Food Safety and the Children’s Environmental Health Network.

“FDA should swiftly ensure that these risky PFCs, which it has already asked domestic producers to stop using, aren’t sneaking into our food supply through pizza boxes or sandwich wrappers made overseas,” said Erik D. Olson, NRDC’s senior strategic director for health and food.

The FDA would neither confirm nor deny receipt of the petition.

In a statement, the FDA said that when it receives a food additive petition, it reviews and responds directly to the petitioner within 15 days, saying whether it “has accepted or not accepted the petition for filing.” If the FDA accepts it, the agency will publish a notice in the Federal Register, opening it up to public comment for 30 days. After that, the FDA may or may not decide to start rulemaking to ban the chemicals.