The Food and Drug Administration allowed 18 animal drugs to stay on the market even after an agency review found the drugs posed a "high risk" of exposing humans to antibiotic-resistant bacteria through the food supply, according to a study released Monday by the Natural Resources Defense Council NRDC, Newsmax Health reports.

NRDC's study found the FDA took no action to remove 30 antibiotic-based livestock feed products from the market even after federal investigators determined many of those antibiotics fell short of current regulatory standards for protecting human health.

The FDA did not immediately respond to a request for comment on the report.

Some academics specializing in antibiotic resistance criticized the NRDC's study, saying that the findings do not reflect current regulatory standards because some of the drugs have been withdrawn from the market.

NRDC attorney Avinash Kar, one of the study's authors, said the group's findings raise questions about whether regulators will be effective in enforcing the new guidelines.