Scientists Worry About Silver-Nano Products
By Cho Jin-seo
Staff Reporter
While electronics companies claim that silver-nano washing machines can effectively kill germs hidden in dirty laundry, scientists suspect they are probably toxic to human cells and other organisms.
Joint research by Korea University and the Korea Institute of Science and Technology (KIST) has uncovered why silver nanoparticles are so powerful and efficient in killing germs. Their findings have led to worries that the microbe particles can damage cells of animals and plants exposed to them.
The study is raising an alarm with Korean companies such as Samsung Electronics, which has been promoting its ``Silver Nano Health System'' washers and air conditioners.
``We are now evaluating how silver nanoparticles affect more complex organisms and the environment,'' said Gu Man-bok, a bioscience professor of Korea University. ``Experiments on rice fishes show that they become toxic in high concentrations.''
Gu said his laboratory was working together with the Ministry of Environment to study the effect of silver-nanoparticles on various life forms ― a belated effort considering consumers are already widely exposed to such products. Silver-nano clothes, cutlery, toys, electronics, face masks and even baby bottles are currently on sale.
The U.S. government is to ban sale of such products from next year if they fail to provide evidence of its safety. But the South Korean government said that it has no plans to regulate the products.
``Since there is no proven ill-effect, it is too early to make regulations to control silver-nano products,'' said Yoon Jun-won of National Institute of Environmental Research.
Silver has been widely recognized as an antiseptic metal. Based on this, ancient Greeks used to store drinking water in silver vessels, and Koreans have preferred silver chopsticks throughout the ages.
Modern technology has enabled companies to maximize this antibiotic property. Smaller particles have a larger surface area than larger particles of the same weight, meaning they can more actively react with other materials. So the companies nowadays use crystallized silver particles measuring one billionth of a millimeter (a nanometer).
To find out how the size of particles matters in their sterilizing effect, Gu and his colleagues used a genetically-modified bacterium that emits various light signals in response to damage suffered. Surprisingly, they found that the silver nanoparticles produce deleterious molecules known as super-oxide radicals, which are not produced from ordinary silver ions.
``Firms like Samsung and LG Electronics started from the idea that silver-nanoparticles kill bacteria and they actually do. But scientists are still unsure of whether they are safe for humans. This field of research is still at a very rudimentary stage,'' said Hwang Ee-taek, a co-author of the paper, which was published in March.
Another co-author said that the researchers were cautious about relating the results to humans, because they were worried about a backlash from the companies concerned. ``This is a very sensitive issue, especially for Samsung,'' he said.
The research was published in March on Small, an academic journal.