Mussels in Puget Sound along the northwest coast of Washington have tested positive for the prescription opioid oxycodone, according to the state’s Department of Fish and Wildlife.

The shellfish also contained antibiotics, antidepressants, diabetes drugs, chemicals found in detergents and cleaning products, and one chemotherapy drug, CNN reports.

Washington Department of Fish and Wildlife biologist Jennifer Lanksbury said the presence of oxyocodone in mussels is an indication of the large number of people in the surrounding urban areas who take the drug. “Some people, unfortunately, flush their drugs down the toilet, and that’s a huge source of these pharmaceuticals,” she noted. “What this is telling us is some of this stuff is coming out of our wastewater treatment plants and so we need to do a better job either at controlling the sources or trying to reduce the exposure in the Puget Sound.”