Medications that are not correctly disposed of can ultimately end up in the water table. This has been noted for decades in scientific literature as trace amounts of various pharmaceuticals are found in the environment including lakes and streams. The United States Geological Society has conducted nationwide measurements of pharmaceuticals, hormones and organic wastewater contaminants in streams across the United States. Their survey found that 80% of the 139 streams surveyed contained a positive sample of one of the contaminants they were monitoring.
A recent news report from May of 2018 found traces of opioids in Seattle-Area mussels and juvenile salmon. In this case, the opioid the team found in the shellfish they tested was oxycodone – an opioid analgesic. These researchers determined that the source of these pharmaceutical contaminants was through discharge from wastewater treatment plants.
You might be wondering why wastewater treatment plants are not preventing drugs from entering the environment. The reality is that wastewater treatment plants filter out solids, sediments, bacteria and viruses but do not generally chemically treat effluent. This means, drugs that end up down the drain or in the landfill can ultimately find their way in to the environment.