Release of Nano-Silver from Textiles into Human Sweat
Researchers in Thailand have demonstrated that fabrics laced with silver nanoparticles release those particles when the fabric is exposed to artificial human sweat. These finding raise concerns about the potential effects of the release of larger amounts of antibacterially active silver on human skin.
Silver nanoparticles are increasingly being added to clothes to reduce bacterial growth and odor. However, there is increasing concern that exposure to these nanoparticles may cause potential adverse effects to humans and the environment.
This study determined the quantity of silver released from commercially claimed nanosilver and laboratory-prepared silver coated fabrics into various formulations of artificial sweat, each made according to AATCC, ISO and EN standards. For each fabric sample, the initial amount of silver and the antibacterial properties against the model Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria on each fabric was investigated.
The results showed that silver was not detected in some commercial fabrics. Furthermore, antibacterial properties of the fabrics varied, ranging from 0% to greater than 99%. After incubation of the fabrics in artificial sweat, silver was released from the different fabrics to varying extents, ranging from 0 mg/kg to about 322 mg/kg of fabric weight.
The team of researchers tested five fabrics that were treated in the laboratory with a silver nanoparticle solution, and six commercially made shirts sold as containing nanosilver. Fabric samples were incubated in different artificial sweat formulations for 24 hours, after which the sweat was analyzed for silver nanoparticles.
The laboratory-prepared fabrics released up to 322 mg/kg of fabric weight with silver particles ranging in size from 200-500 nanometers. The commercially made shirts released far less, as they contained less silver to begin with - and some of the shirts labeled as "nanosilver" did not actually contain any silver.