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New research has found low levels of various medicines — antibiotics, antihistamines, and pain relievers — as well as carcinogenic chemicals and mercury in oysters that grow in two Oregon bays.

The findings do not suggest any immediate risk to human health, but one study author said more analysis is needed to determine the extent to which such contaminants might affect the oyster population and, by extension, a need for better wastewater treatment.

“If you’re allergic to one of these medicines, we’re not sure how many oysters you would have to eat to have a reaction,” said Elise Granek, an associate professor of environmental science and management at Portland State University, who is one of the coauthors of the study, which was recently published in the journal Science of the Total Environment.


“But for any at-risk population, it’s helpful to have this information, such as children or people with certain allergies or immune disorders,” she continued. “The problem is that we don’t know how these things interact in the body of a plant or an animal. So how do we minimize the concentration of pharmaceuticals and chemicals going into the oysters?”

Pharmaceuticals and chemicals are believed to enter the bays through groundwater runoff and wastewater that is discharged to inland rivers and eventually find their way to the ocean. Among the medicines that were detected were various antibiotics, including azithromycin; the ibuprofen and naproxen pain relievers; and the active ingredient in Benadryl, an antihistamine.


The research is the latest reminder of the impact that pharmaceuticals can have on bodies of water.

“Numerous studies intimate that unintended exposure to certain drugs, such as antibiotics and endocrine disruptors, or a synergistic combination of pharmaceutical substances, may cause adverse health impacts for humans,” Gabriel Eckstein, a Texas A&M University law school professor who specializes in environmental law, wrote in the NYU Environmental Law Journal last year.

The findings also come amid growing concern among local and state governments about contaminants in their water supplies. Although drug take-back programs are seen as part of the solution, many governments are trying to defray the cost by passing laws that require drug makers to finance these efforts. The pharmaceutical industry, however, has been resisting.

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