Sarah DeWeerdt: Leaky Sewers a Source of Pollution


“Wastewater treatment facilities are not equipped to remove many pharmaceutical compounds,” lead author Emma Rosi, an aquatic ecologist at the Cary Institute of Ecosystem Studies, a nonprofit research organization in Millbrook, NY, said in a press release. “We were interested in how stream microorganisms – which perform key ecosystem services like removing nutrients and breaking down leaf litter – respond to pharmaceutical pollution.” Rosi and her colleagues studied biofilms—complex assemblages of bacteria and algae that make rocks and leaves in streams slippery – in four waterways in and around Baltimore, Maryland.

The study sites represent an urban-to-suburban gradient of habitats, and they each harbor a different assemblage of microbes, the researchers found. The biggest differences were between Gwynns Run, the most urbanized stream with a documented history of sewage contamination, and Gwynnbrook, the least developed stream.

First, the researchers looked for six different drugs in the streams: acetaminophen, caffeine, sulfamethoxazole (an antibiotic), diphenhydramine (an antihistamine), amphetamine, and morphine. They detected all of the drugs in all four streams, with the highest concentrations in the most urbanized stream and the lowest concentrations in the least urbanized stream.