You may or may not be aware of this, but silver nanoparticles (aka nanosilver) are special. They carry the beautiful “nanoparticle” buzzword, which means they must be special in some way (otherwise they would not be called nano) and they have antimicrobial properties. Nanosilver has been used in a vast array of consumer products to provide antimicrobial protection. This isn’t news. Silver salt (silver nitrate, actually) was used to help prevent and cure infections before the discovery of penicillin and is still used on burn victims. That’s one reason why some people drink colloidal silver (another word for a suspension of nanoparticles) as a dietary supplement.
But silver nanoparticles have not yet been proven to be safe for humans and the environment. There still are contradicting views in recent in vivo and in vitro studies involving silver nanoparticles. The most likely adverse effect of ingesting silver nanoparticles is a permanent cosmetic condition called argyria, in which a person’s body bioaccumulates silver in the dermis, giving it a blueish-grey hue. But when inhaled, silver nanoparticles, like most kinds of airborne particles, may deposit in the respiratory system and cause damage to the lungs and cardiovascular system.
Because we saw how many consumer products claiming to contain silver or silver nanoparticles were already available in the market, many of those catered to children, we decided to continue our quest for sustainable nanotechnology by studying the amount and type of silver (ionic or particulate) to which a child could become exposed while using these products in real-world situations.
We investigated the presence and release of silver in a number of products (plush toy, fabric products, breast milk storage bags, sippy cups, cleaning products, humidifiers, and humidifier accessory) into different biologically-relevant liquid media (water, orange juice, milk formula, sweat, urine, and saliva). We also let a few products sit outside, rubbed them into a concrete block, and exposed them to a UV lamp to promote aging to see if that affected the release of silver.
Our main results indicate that the release of silver from consumer products is very low (about 5% of silver present got released into liquid media in one of our scenarios) and is mainly driven by dissolution, which means that the consumer is more likely to be exposed to silver ions, not nanoparticles. We also found that the amount of silver that is released by products, and thus might be internalized by a consumer, heavily depends on the biological media involved. Sweat, because it’s more salty, yields a higher silver release than, for example, saliva.
So, nanosilver is likely not to be harmful for consumers, they might even be a better option than other more harmful antimicrobial chemicals and antibiotics. But I think this brings a nice opportunity for discussion about antimicrobial products. Our generation has seen such a boom in antimicrobial products that I feel we might be buying some without even realizing it. And, as much as it may help most of us feel safer by killing potentially harmful bacteria, we might also be ridding our homes of a healthy microbiota. Jessica Green has a great 5-min TED talk about what we’re doing with the air microbiota of hospitals when we try to filter everything out.
Now it’s your turn to add to the discussion:
Do you use antimicrobial products (with nanosilver or other kinds) in your home? How do you feel about them? Post your comment below!
For more information on this project:
See our newly-published paper on Environmental Science & Technology:
Quadros, Marina, Pierson Iv, Raymond, Tulve, Nicolle, Willis, Robert, Rogers, Kim, Thomas, Treye, & Marr, Linsey (2013). Release of silver from nanotechnology-based consumer products for children. Environmental Science & Technology. doi: 10.1021/es4015844
Or contact Dr. Marina Vance
Other VTSuN research involving silver nanoparticles:
Kent, Ronald D., & Vikesland, Peter J. (2011). Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy. Environmental Science & Technology. doi: 10.1021/es203475a
Quadros, Marina E., & Marr, Linsey C. (2011).Silver Nanoparticles and Total Aerosols Emitted by Nanotechnology-Related Consumer Spray Products. Environmental Science & Technology, 45(24), 10713-10719. doi: 10.1021/es202770m
Quadros, Marina E., & Marr, Linsey C. (2010).Environmental and human health risks of aerosolized silver nanoparticles. Journal of the Air & Waste Management Association, 60(7), 770-781. doi: DOI 10.3155/1047-32126.96.36.1990
About the Author: Marina Vance is the Associate Director for VTSuN: Virginia Tech’s Center for Sustainable Nanotechnology and a postdoctoral associate of the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech.
Update [2 Sep 2014] Nina Quadros has recently changed her name to Marina Vance
On twitter: @marinavance