Smelly feet may be the price we have to pay for saving the planet. A new study reported by New Scientist has discovered that nanoparticles commonly found in antibacterial socks may be inadvertently raising levels of greenhouse gases.


Researchers are concerned that silver nanoparticles — antibacterial agents used in a range of products, including odor-free socks — have been escaping into the water system and killing friendly bacteria often used to treat wastewater.


"We are trying to find out what happens when these silver nanoparticles get into the real environment," said Benjamin Colman, a chemist from Duke University who conducted the study. "These particles are developed with the express purpose of killing things."


Previously, all research done on the environmental impacts of silver nanoparticles has been limited to their effects on a single microbe species within a lab. To better mimic the impact of silver in a real setting, Colman and colleagues instead looked at how high dosages affected a sample of stream water and soil in the lab. They also set up two outdoor tubs, one filled with nanoparticle-free sludge as a control, and another dosed with a concentration of nanoparticles similar to levels found in wastewater.


What they found was that microbial populations in the samples contaminated with silver were significantly lower after just one week, and enzyme activity (which measures how much organic matter the microbes are capable of breaking down) was down by 34 percent.


Perhaps most alarming, though, was the discovery that microbes in the tub containing silver nanoparticles also produced four times more nitrous oxide than the control tub. Since nitrous oxide is a greenhouse gas, this means contaminated wastewater could increase the effects of global warming if nanoparticles are used on a large scale.


These results could "further contribute to concerns about global changes in climate," said Donald Wuebbles, an atmospheric scientist at the University of Illinois. He added that nitrous oxide can also harm the ozone layer.


The next step for researchers is to test how silver nanoparticles can affect a real wetland ecosystem, should contaminated water also escape into nature.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Antibacterial socks kill odor and ice caps
New study finds that nanoparticles commonly used in antibacterial socks may significantly boost greenhouse gas emissions.