(Beyond Pesticides, September 3, 2010) New research shows that silver nanomaterials, which are used in a number of consumer products as antimicrobial agents, can interrupt important cell signaling within male reproductive sperm cells, causing them to stop growing. In previous studies, scientists reported how smaller-sized silver nanoparticles — in the 10 – 25 nanometer range — decrease the growth of male stem cells when they are exposed at concentrations greater than 10 micrograms per milliliter (Î¼g/ml). This new study, on the other hand, is the first to identify how the silver nanoparticles stop the sperm stem cells from growing, with the biggest effects from the smallest-sized nanoparticles tested. Like many other studies on the effects of nanotechnology, this study raises important questions about the potential hazards to human health due to the prolific use of silver nanoparticles in the market.
Researchers tested the effects of different sizes, concentrations and coatings of silver nanoparticles on cell growth of mouse sperm cells. They compared silver nanoparticles coated with either hydrocarbons — at 15 nm, 25 nm and 80 nm diameters — or sugars — at 10 nm, 25 – 30 nm and 80 nm diameter. Exposure to the smaller sized particles led to increased stem cell death. The sugar coatings on the smaller-sized silver nanoparticles increased the production of reactive oxygen species (ROS), one of the signals for induced cell death.
One important pathway known for sperm stem cell growth is the growth factor glial cell line-derived neurotrophic factor (GDNF). Though the amount of GDNF was not changed, the signals sent to the cell were damaged after silver nanoparticle exposure. The researchers found that a small protein, Fyn kinase, is not fully functional. This protein requires a modification in order to function, and that modification is reduced when cells are exposed to silver nanoparticles.
Additionally, researches believe that exposure during development may affect forming sperm cells and lead to birth defects related to the male reproductive system. Scientists believe this is because the small silver particles can cross the mother’s placenta and directly affect the baby.
Silver nanoparticles are now widely impregnated into a wide variety of consumer products to kill off bacteria, including cosmetics, sunscreens, sporting goods, clothing, electronics, baby and infant products, and food and food packaging. However, little is known about the impact of nanoparticles on human health and the environment, and mounting evidence suggests that these materials can pose significant health, safety, and environmental hazards. Nanosized particles can be released from impregnated materials via washing or sweating where they may pose numerable unknown adverse effects to humans and water systems.
Though the use of silver nanoparticles typically falls under the Federal Insecticide, Fungicide, and Rodenticide Act’s (FIFRA) definition of a pesticide as substances intended to kill pests such as microorganisms, EPA does not currently regulate it as such. In 2008, the International Center for Technology Assessment (ICTA), the Center for Food Safety, Friends of the Earth, and others including Beyond Pesticides filed a legal petition http://www.beyondpesticides.org/dailynewsblog/?p=340 challenging EPA’s failure to regulate nanosilver as a unique pesticide. The 100-page petition addresses the serious human health concerns raised by these unique substances, as well as their potential to be highly destructive to natural environments, and calls on the EPA to fully analyze the health and environmental impacts of nanotechnology, and require labeling of all products.
On August 13th, EPA announced its proposal to conditionally register a pesticide product containing nanosilver as a new active ingredient for a period of 4 years. Comments are due on September 11, 2010. EPA is proposing the antimicrobial pesticide product, HeiQ AGS-20, is a silver-based product that is proposed for use as a preservative for textiles. Under its new policy concerning public involvement in registration decisions, EPA is providing a 30-day opportunity for public comments on the proposed registration. As a condition of registration, EPA is proposing to require additional product chemistry, toxicology, exposure, and environmental data. The Agency will evaluate these data as they are submitted during the period of the conditional registration.
EPA also announced a 45-day public comment period for the draft document “Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray” (EPA/600/R-10/081). The document is being issued by the National Center for Environmental Assessment within EPA’s Office of Research and Development. EPA is releasing this draft document solely for the purpose of pre-dissemination review under applicable information quality guidelines. This document has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency policy or determination. The draft document is available via the Internet on the NCEA home page under the Recent Additions and the Data and Publications menus at http://www.epa.gov/ncea.
The draft is intended to serve as part of a process to help identify and prioritize scientific and technical information that could be used in conducting comprehensive environmental assessments of selected nanomaterials. It does not attempt to draw conclusions regarding potential environmental risks of nanoscale silver; rather, it aims to identify what is known and unknown about nanoscale silver to support future assessment efforts. When finalizing the draft document, EPA intends to consider any public comments that EPA receives in accordance with this notice. Technical comments should be in writing and must be received by EPA by September 27, 2010
Source: Environmental Health News