Medicines that have long been marketed as beneficial for humans are having decidedly different effects on other species. As we take more, they take more as well; 12.7% of Americans over the age of 12 now take antidepressants, up from 7.7% about two decades ago. And researchers are finding correspondingly higher levels of the drugs in fish.
Scientists from the University of Buffalo have documented high levels of antidepressants and other drugs in the brains of fish in the Great Lakes. Two years ago, a study by the NOAA Fisheries’ Northwest Fisheries Science Center and the University of Washington found similar results in the Puget Sound. The source in both cases is effluent from wastewater treatment plants, which do not filter out the drugs. The drugs can be detected in the water itself, but they accumulate in the brains of fish, which show levels up to 20 times higher than in the water.
What exactly are the effects of the drugs? The results are mixed: As this article reports, “Fish respond similarly to humans on antidepressants. They are less risk-averse and, it appears, happier.” Their decreased sense of danger, though, makes them more likely to be eaten by predators. “These sorts of changes could trigger the collapse of an entire fish population, or even seriously disrupt the biodiversity of the lakes—the largest freshwater ecosystem in the world,” according to the article.
Other effects are just as disturbing. Researchers at McMaster University have shown that as fish are exposed to more toxins—not only antidepressants but also contraceptives and various chemicals found in personal care products—they expend more energy to deal with the effects, leaving less energy for growth and reproduction.
The article suggests that improved oxidation processes—which would involve expensive upgrades to the treatment plants—could filter out a good portion of the drugs, but upgrading the 1,400 or so treatment plants surrounding the Great Lakes alone would be costly, and communities don’t yet see a strong enough incentive to make that investment.