Antihistimines are drying up rock-coating algae
By Summit Voice
SUMMIT COUNTY — Antihistimines used to treat allergies do more than dry up runny noses. Remnant traces of the pharmaceuticals, now commonly found in many streams and rivers, are having a significant effect on basic biological processes, with as-yet unknown impacts on aquatic life and water quality.
“Pharmaceutical pollution is now detected in waters throughout the world. Causes include aging infrastructure, sewage overflows, and agricultural runoff, said Dr. Emma Rosi-Marshall, a scientist at the Cary Institute of Ecosystem Studies, lead author of a study that examined how common pharmaceuticals influenced similar-sized streams in New York, Maryland, and Indiana.
The study looked for traces of Caffeine, the antibiotic ciprofloxacin, the antidiabetic metformin, two antihistimines used to treat heartburn (cimetidine and ranitidine), and one antihistamine used to treat allergies (diphenhydramine).
“Even when waste water makes it to sewage treatment facilities, they aren’t equipped to remove pharmaceuticals. As a result, our streams and rivers are exposed to a cocktail of synthetic compounds, from stimulants and antibiotics to analgesics and antihistamines,” Rosi-Marshall said.
The most striking result of the study was diphenhydramine’s effects on algal production and microbial respiration. Exposure caused biofilms to experience up to a 99 percent decrease in photosynthesis, as well as significant drops in respiration. Diphenhydramine also caused a change in the bacterial species present in the biofilms, including an increase in a bacterial group known to degrade toxic compounds and a reduction in a group that digests compounds produced by plants and algae.
“We focused on the response of biofilms – which most people know as the slippery coating on stream rocks – because they’re vital to stream health,” she said. “They might not look like much to the naked eye, but biofilms are complex communities composed of algae, fungi, and bacteria all living and working together. In streams, biofilms contribute to water quality by recycling nutrients and organic matter. They’re also a major food source for invertebrates that, in turn, feed larger animals like fish.”
Results suggest that this antihistamine is disrupting the ecology of these sensitive biofilm communities.
“We know that diphenhydramine is commonly found in the environment. And its effect on biofilms could have repercussions for animals in stream food webs, like insects and fish. We need additional studies looking at the concentrations that cause ecosystem disruption, and how they react with other stressors, such as excess nutrients.” she said.
The other pharmaceuticals investigated also had a measurable effect on biofilm respiration, both alone and in combinations. More work is needed to understand how drug mixtures, which most natural streams experience, impact freshwater systems.