Pharmaceuticals in Streams
From: Andy Soos, ENN.com
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 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.
