Are Silver Nanoparticles in Clothing Safe?

Silver nanoparticles are woven into high-tech athletic clothing as a means of controlling bacteria and odors.  Silver has low toxicity for people, but is able to kill bacteria.  How it kills bacteria is not completely understood, but it is believed to cause oxidative stress.  Oxidative stress is harmful for us as well, but bacteria can be killed at lower levels than can hurt us.  Still, oxidative stress is not good.  That's why anti-oxidants are protective against cancer and effects of cell damage.  Silver nanoparticles are used in topical antibiotics to treat life threatening infections in burn patients.  Better to risk a little oxidative stress from silver nanoparticles than to die from an infection. 

So, is it a good idea to put silver nanoparticles in clothes? No one knows the answer to this question.  But there are a few answers to a few related questions.  For example, do the silver nanoparticles embedded in fabrics some off the cloth and end up in wastewater?  Do the particles come off the cloth and enter peoples bodies? Are there any known health effects from exposure to silver nanoparticles?  If the particles stay in the fabric there is probably little to worry about.  Let's take a look:

• Do Silver nanoparticles come off the fabrics in which they are embedded?  Apparently they do, but different fabrics lose nanoparticles at different rates, at least during the wash cycle. Benn TM, & Westerhoff P (2008). Nanoparticle silver released into water from commercially available sock fabrics. Environmental science & technology, 42 (11), 4133-9 PMID: 18589977
•  Can silver nanoparticles be absorbed through people's skin?  Apparently they can.  Silver nanoparticles are being used a a topic anti-biotic in burn patients.  Infection is a major, major factor in recovery (and mortality) for burn patients.  Brandt O, Mildner M, Egger AE, Groessl M, Rix U, Posch M, Keppler BK, Strupp C, Mueller B, & Stingl G (2012). Nanoscalic silver possesses broad-spectrum antimicrobial activities and exhibits fewer toxicological side effects than silver sulfadiazine. Nanomedicine : nanotechnology, biology, and medicine, 8 (4), 478-88 PMID: 21839058
  
• How long do silver nanoparticles stay in a person once they get there?  This is an important question.  If they stay around a long time, they can do damage for a long time.  If they leave quickly they would be less dangerous.  Same thing goes for a lot of other substances.  The answer to this question appears to be unknown 
• Are there any known health effects if silver nanoparticles are absorbed?  Lim DH, Jang J, Kim S, Kang T, Lee K, & Choi IH (2012). The effects of sub-lethal concentrations of silver nanoparticles on inflammatory and stress genes in human macrophages using cDNA microarray analysis. Biomaterials, 33 (18), 4690-9 PMID: 22459196.  Silver nanoparticles appear to have harmful effects on some human (and animal) cells.  (Comparative in vitro cytotoxicity study of silver nanoparticle on two mammalian cell lines- citation)

While its been demonstrated that the particles can harm cells, tissues or organs we don't know how much would be needed to harm health.  The amount of silver nano-particles absorbed from clothing may not be high enough to matter.  Its an unanswered question.   We'll probably hear more about this in coming years.  For now you'll have to rely on your own judgement.