Resolving to clean out your medicine cabinet this year is a good idea. Hanging onto unused medications can increase the chances of taking the wrong one, and old drugs can lose their potency, reports the Harvard Heart Letter. But have you ever thought about where the medicine will end up? Scientists are finding everything from aspirin to Zoloft in our streams, rivers, and lakes.

The traditional advice has been to flush unused drugs down the toilet or put them in the trash. Neither is a good method, says the Harvard Heart Letter. Drugs can kill helpful bacteria in septic systems and pass largely untouched through sewage treatment plants. Children and animals can get into drugs tossed in the trash, and once in landfills, drugs can trickle into groundwater.

Regulations prohibit medication recycling. However, there are a few innovative drug disposal programs, in which citizens can drop off medications along with household hazardous waste, mail unused drugs to their state’s Drug Enforcement Agency, or donate drugs to the needy.

What can you do to ensure safe drug disposal? The Harvard Heart Letter offers these suggestions:

1. Ask your pharmacist if he or she can take back medications.
2. Call your city or state to ask about disposal programs like those mentioned above.
3. If you need to put your medications in the trash, keep them in their original childproof and watertight containers. Leave the label on, but scratch out your name to protect privacy. Add some water to pills, and put some flour in liquids. Conceal the vials by putting them in empty margarine tubs or paper bags before throwing them out.