New Study Finds that the Silver Sprayed on Your Socks Ends Up in the Soil

July 18, 2012

by Ashley Hofmann, HSC public policy intern

Ashley Hofmann is completing the final practicum to earn her Masters of Social Work from the University of Missouri. Her academic research and passion focuses on disparities in access to healthcare and how policy can act as a catalyst for social justice. As a summer intern at HSC, Ashley is researching best-practices for student health and wellness and advocating for support of healthy foods in the 2012 Farm Bill.  

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Did you know the ancient Greeks used silver pots to keep their drinking water clean and safe? While they may not have been aware of the spread of microscopic bacteria, they did recognize the important role silver plays in disease prevention.

That same strategy is now being applied (literally) to hundreds of everyday consumer goods. Silver nanoparticles, an emerging form of antibacterial protection, are being included in the production of items such as athletic wear, toothbrushes, and washing machines. But what happens when the nanoparticles are washed down the drain?  

THE STUDY ON SILVER

To find out, a group of researchers set up a test site in North Carolina. They added silver nanoparticles to the soil and water, then took samples over an 18-month period. The final analysis found that silver accumulated in plants growing in the soil, as well as in animals living in the water. This was even the case for plants that started growing six months after the silver was applied.  

Also of note in this study is how the nanoparticles changed over time. In samples from both the soil and water, over half of the silver reacted with sulfur to form silver sulfide (the chemical name for the tarnish on your silver jewelry).

This is one of the first long-term studies of its kind. It hasn’t been determined if the silver accumulation is good or bad for our health or the environment. Past research has shown that silver can be harmful to fish by causing reproductive problems, but more information is needed about how the high levels of silver affect other species and the ecosystem as a whole. 

USING SILVER IN SCHOOLS

Schools may be thinking about whether or not products that contain silver are an optimal choice for disinfecting their facilities. When it comes to controlling the spread of germs and bacteria in a sustainable manner, HSC encourages school administrators to follow three steps for healthy students:

  1. prevent infection through hygiene education
  2. develop a green cleaning program
  3. disinfect only when necessary 

In the third step of disinfecting, HSC recommends using the least toxic product for the job, and while silver nanotechnology can be an appropriate disinfectant for some situations, there are a few things to consider. First, we believe more research needs to be performed on the long-term risks associated with increased silver concentrations in the environment before this new technology can be endorsed for all situations. Second, schools should try to purchase concentrated products over Ready-to-Use (RTU) formulas — which silver disinfectant sprays tend to come in — to minimize the environmental footprint of transportation and packaging in RTU products. And third, the cost of silver nanotechnology is still significantly higher than other methods, which may make them impractical for schools.

HSC looks forward to further research on the issues of silver nanoparticles in the hopes that we will be able to fully benefit from this new application of an old technology. Until then, we’ll focus our recommendations on promoting hygiene, good cleaning practices, and minimizing exposures to any disinfectant product.

The abstract of the study in North Carolina is available here