First author Sherri Cook, a doctoral student at the University of Michigan, and Nancy Love, a professor in the department of civil and environmental engineering, compared the total emissions created by take-back, trash and toilet disposal methods of leftover medications.
In most cases, the U.S. Food and Drug Administration recommends throwing the medications away, but only if people don't have access to a take-back program. Flushing unused pills down the toilet is no longer advised, as the active ingredients in drugs have been found in drinking water and aquatic environments, but about 40 percent still flush unused medication down the toilet, Cook explained.
In medication take-back programs, the returned drugs are incinerated as hazardous waste, Cook said.
"National policy seems to be changing to support take-back programs, and we don't know if that's justified," Cook said in a statement.
The study, published in Environmental Science & Technology, found if everyone trashed their extra drugs, the amount of active pharmaceutical ingredients in the environment would be significantly reduced.
The researchers encourage policymakers to focus on getting more people to get rid of medicines by trash, rather than take-back.