02 April 2013

Streams stressed by pharmaceutical pollution

Pharmaceuticals commonly found in the environment are disrupting streams, with unknown impacts on aquatic life and water quality.


So reports a new Ecological Applicationspaper, which highlights the ecological cost of pharmaceutical waste and the need for more research into environmental impacts.

Lead author Dr Emma Rosi-Marshall, a scientist at the Cary Institute of Ecosystem Studies, comments: "Pharmaceutical pollution is now detected in waters throughout the world. Causes include ageing infrastructure, sewage overflows, and agricultural run-off. 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."

How the study was done

With colleagues from Indiana University and Loyola University Chicago, Rosi-Marshall looked at how six common pharmaceuticals influenced similar-sized streams in New York, Maryland, and Indiana. Caffeine, the antibiotic ciprofloxacin, the antidiabetic metformin, two antihistimines used to treat heartburn (cimetidine and ranitidine), and one antihistamine used to treat allergies (diphenhydramine) were investigated, both alone and in combinations, using pharmaceutical-diffusing substrates.      

Rosi-Marshall explains, "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. 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."

Healthy streams are slippery streams. And it turns out that antihistamines dry more than our noses. 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% 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.


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