Your toilet bowl may be the time-honored venue for dumping expired or unused drugs, but your local waterways could suffer for it. The U.S. Geologic Survey has been studying the nation's waterways for years, and an exhaustive study in 2002 detected trace levels of chemicals commonly found in prescription drugs in 80 percent of the streams tested across the country. Now, under pressure from researchers who suspect hormones and antidepressants may be responsible for harming fish, the U.S. Environmental Protection Agency is on the march to gauge the health and environmental impact of pharmaceuticals in water. In the last year, says EPA press officer Suzanne Ackerman, the agency has made some "ground­breaking" advances and is testing methods that may be effective in removing pharmaceuticals from the water. The going is slow, she concedes, but "it's happening." Meanwhile, what should you do with your unused drugs? There are no government guidelines, so pharmaceutical experts recommend: 1. Find out if your local pharmacies take back medications. Some have occasional days designated for such drop-offs. 2. Check to see whether your area has a community household hazardous waste collection program. 3. Go to www.epa.gov/epahome/state.htm for local numbers.