Pharmaceuticals in Streams
Pharmaceuticals commonly found in the environment are found in streams, with unknown impacts on aquatic life and water quality. So reports a new Ecological Applications paper, which highlights the ecological cost of pharmaceutical waste and the need for more research into environmental impacts. Pharmaceuticals, or prescription and over-the-counter medications made for human use or veterinary or agribusiness purposes, are found often in the environment. Antibiotics,vitamins, supplements, and sexual enhancement drugs are contained in this group. These products typically enter the environment when passed through the body and then entering into the ground or sewer lines, or when disposed of in the trash, septic tank, or sewage system.
A study by the U.S. Geological Survey report published in 2002 found detectable quantities of pharmaceuticals in 80 percent of a sampling of 139 susceptible streams in 30 states. The most common pharmaceuticals detected were steroids and nonprescription drugs. A 2006 study found detectable concentrations of 28 pharmaceutical compounds in sewage treatment plant effluents, surface water, and sediment. The therapeutic classes included antibiotics, analgesics and anti-inflammatories, lipid regulators, beta-blockers, anti-epileptics, and steroid hormones. Although most chemical concentrations were detected at low levels (nano-grams/Liter (ng/L)), there are uncertainties that remain regarding the levels at which toxicity occurs and the risks of bioaccumulation of these pharmaceutical compounds
Lead author Dr. Emma Rosi-Marshall in the new study, a scientist at the Cary Institute of Ecosystem Studies, comments: "Pharmaceutical pollution is now detected in waters throughout the world. Causes include aging infrastructure, sewage overflows, and agricultural runoff. 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."
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.
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."
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance. Biofilm, which is also referred to as slime (although not everything described as slime is a biofilm), is a polymeric conglomeration generally composed of extracellular DNA, proteins, and polysaccharides. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings.
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.
For further information see Stream Pharmaceuticals.
Biofilm image via Wikipedia.