New FDA draft guidance shows the regulator may tighten application rules for drugs that contain hormones or that may interact with them, reported Regulatory Focus.

The new rules would impact manufacturers that make drugs with estrogenic, androgenic or thyroid activity.

The guidance updates environmental rules from 1969 that require government agencies to make environmental assessments of the industries and activities they oversee. Although the FDA requires some companies to submit environmental assessments with new drug applications, there are exceptions for reasons that include how diluted the drug would be if it entered the water supply (based on parts per billion) and if it is a product that naturally exists in the environment.

The draft guidance focuses on the drug’s concentration at the point of entry into water because research has found “drugs with estrogenic, androgenic or thyroid activity have the potential to cause developmental or reproductive effects in the aquatic environment” at levels even below one part per billion.

The FDA will accept comments on the guidance for 60 days.

Correction: A previous version of this article incorrectly described the focus of the draft guidance. The draft guidance focuses on the drug’s concentration at the point it enters the water. We apologize for the error.