Nanosilver: Environmental Effects
Some of the most worrying impacts from the widespread use of silver nanotechnology are its impacts on the environment, especially to ecologically important organisms. Once in the environment, it is possible for nanoparticles to move from one environmental compartment to another, i.e. from water to sediment, soil to groundwater, from water to microorganisms, fish, insects or mammals. Nanoparticles may also interact with other compounds in the environment, partaking in environmental chemical and biological reactions. The implications of these interactions are still unclear.
How Do Silver Nanoparticles End Up in the Environment?
Down the Drain
According to Samuel Luoma, PhD, at the John Muir Institute of the Environment at the University of California, Davis in his report for the Project on Emerging Nanotechnologies at the Woodrow Wilson International Center for Scholars called “Silver Nanotechnologies and the Environment: Old Problems or new Challenges?” states that nearly one-third of nanosilver products on the market in September 2007 had the potential to disperse silver or silver nanoparticles into the environment. Cosmetics, personal grooming products and household cleaning products among others, when washed down the drain disperse nanoparticles into wastewaters. Textiles and clothing imbedded with nanoparticles, when laundered, release these particles into the wash cycle and they eventually make their way into waste and surface waters. A recent study found that socks impregnated with silver nanoparticles to keep them microbe and odor free, release these particles when washed. Some lost the bulk of their nanosilver after two to four washings.
Nanosilver particles have been found in sewage sludge at water treatment plants, indicating that these particles have indeed entered the water system. The environmental risks are not clear however. Many particles may aggregate or associate with other ions or materials in the environment and deposit into sediments and soils. Some however, can remain in surface waters, where they can be absorbed and /or ingested by aquatic organisms. Microbial populations especially those in waste water treatment plants (WWTPs) are vulnerable to silver nanoparticles contamination. Silver nanoparticles inhibit the growth of bacteria and other microorganisms, essential to the waste water treatments process. Similarly, these particles also threaten aquatic and terrestrials populations of microbes at the corner stone of many ecosystems. Nanoparticles may also enter the bodies of shellfish, fish and even aquatic plants. Their ability to be easily taken into the bodies of organisms indirectly exposes humans and other higher mammals to nanoparticles absorbed by these species, especially through the ingestion of filter feeding organisms such as mollusks.
A major challenge for this new technology is the development of protocol to detect and investigate the behavior of nanoparticles in the environment and how they impact biological systems. It is unclear how many silver nanoparticles have been released into the environment, and it is imperative that the environmental risks of these particles be properly assessed in order to protect human and environmental health.