The chemicals in medications can cause hormonal changes and affect aquatic organisms at the cellular level, Parson said. Drugs intended to lower people's cholesterol, for instance, can retard metabolism and growth in fish, and antipsychotic and anxiety medications can impact behavior, growth and reproduction.
"Fish may be expressing different hormones that they wouldn't normally," Parson said. "We don't want any kind of impurity in any of our waters. Pharmaceuticals are just one of those potential substances."
However, people shouldn't depend on a waste treatment plant to remove pharmaceutical chemicals from wastewater, either. "Most treatment facilities don't have the technology to filter out these substances from sewage," Parson said.
That's led experts to suggest that the best way to get rid of expired medications is to throw them away in the household trash.
Take-back programs do exist -- with expired drugs being collected and disposed of by pharmacies, government agencies or community groups -- but most aren't meant for consumers, Delafuente said.
"At the retail or pharmacy level, they can have a pick-up service come, collect the old medications and dispose of them, usually by incineration," he said.
However, some medications are just too risky to be put in the trash and should, instead, be flushed, according to the U.S. Food and Drug Administration. These include controlled substances such as methadone, OxyContin, Percocet and Dilaudid. Flushing such drugs, the agency says, ensures that they won't fall into the wrong hands. Some drugs on the list could be fatal if taken by someone who doesn't need the medication, the FDA warns.
Medications disposed of in the
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