These are the findings of scientists who are measuring the impact that pharmaceuticals are having on our aquatic friends. As The Scientist notes, “excreted from our bodies, small amounts of medications make their way through wastewater treatment plants and into the effluent pumped into rivers and streams.” So researchers are looking for traces of common meds that millions of people take every day, such as contraceptives, antidepressants, painkillers and cholesterol fighters.

For instance, Peter Fong, a biologist at Gettysburg College in Pennsylvania, found that Prozac began inducing premature spawning in male zebra mussels at levels of 20 ng/ml of water (nanograms per milileter). Toxicologist Marsha Black, at the University of Georgia, found that the antidepressant exposure at the level of 6 parts per billion delayed development in mosquito fish.

Karen Kidd, of the University of New Brunswick, reported recently that chronic low-level exposure to ethanyl estradiol, the estrogen mimic commonly found in contraceptive patches and pills, so damaged reproductive development in fathead minnows that the population in an experimental lake was nearly extinguished by the end of her seven-year study.

Jim Gelsleichter, a biologist at the Mote Marine Laboratory in Sarasota, calls this chemical “poster child for the pharmaceutical problem.” He’s found trace amounts of six SSRIs: Of ten sharks sampled, one tested positive for all six, and nine tested positive for Zoloft. Gelsleichter stresses that the concentrations discovered were very low, about 0.4 ng/ml of blood. (For comparison, a person taking Zoloft might expect blood levels of 30-200 ng/ml, he says.) Perched at the top of the food chain, bull sharks keep smaller fish numbers in check; what happens to them could ripple through the entire ecosystem, Gelsleichter adds.

Gelsleichter and a colleague, Nancy Szabo, have expanded their study to look for additional chemicals, including those found in cholesterol-lowering meds such as Lipitor. “Cholesterol is the precursor for all the sex hormones,” Szabo tells The Scientist, and “cholesterol-lowering drugs could potentially be devastating for wildlife.”

For now, he’s still in the process of identifying candidate “problem drugs” that warrant closer study. “It’s somewhat of a fishing expedition,” says Gelsleichter, “if you’ll excuse the pun.”