Marsha Black has learned that sometimes the best way to see the big picture is to study the small details. The University of Georgia ecotoxicologist has examined water-quality issues for decades, spending most of that time trying to better understand the biological impact that pollutants can have on even the tiniest of aquatic organisms. Recently, she has turned her attention to a new concern — the steady deposit of antidepressant drugs such as Prozac into wastewater, their ultimate presence in creeks, streams, and other surface waters, and the consequent effects of these chemicals on wildlife.

Ironically, when Black’s collaborator, Mississippi State University scientist Kevin Armbrust, was younger, his father used to joke that “the world would be a better place if its drinking water supply had a little bit of Prozac in it.” But while Prozac and related medications offer hope to millions of people who experience a range of mental-health problems, such drugs have properties similar to other pollutants when they wind up in unintended places. And the damage they wreak on aquatic species there could be just as great. Black and Armbrust are discovering, for example, that when certain types of fish and frogs are exposed to “a little bit” of these medications, they experience problems that include slowed rates of development and a sluggish state that leaves them vulnerable to predators.

The intricate relationships among animals and plants that make up an ecosystem depend upon a certain balance. Therefore the question that haunts Black, Armbrust and others is: What happens to those organisms — and to us — if that balance is upset? “We used to think that only compounds in the water would harm humans, and only through direct exposure,” Black said. But scientists have come to realize that the harm may occur indirectly by disrupting ecological biodiversity.

Chemicals Out of Place

Up to 90 percent of many prescription drugs that humans consume ultimately find their way to sewage-treatment plants. While treatment plants that process drinking water remove these chemicals and their metabolic byproducts, these compounds pass through sewage-treatment facilities, which are designed to remove solids and bacteria but are not equipped to screen for pharmaceuticals. Armbrust, who is also the state chemist for Mississippi, was particularly taken aback by a 1999 paper in the journal Environmental Health Perspectives that documented a steady stream of pharmaceuticals — including Prozac and other selective serotonin re-uptake inhibitors, or SSRIs — being passed into the nation’s waters. SSRIs are among the 200 most-prescribed medications in the United States; the number of adults taking antidepressants has nearly tripled since Prozac was first introduced to the market in 1987, according to the Centers for Disease Control and Prevention.