Dr Bernd Nowack and colleagues from the Swiss Federal Laboratories for Materials Testing and Research studied the release of nanoparticles in laundry water from nine different textiles - including different brands of anti-odour socks - noting that the widespread use of silver nanoparticles in consumer products is likely to result in the distribution of the nanoparticles in lakes and streams.

However, Dr Nowack told Laboratory News: “There is not much release of nanoparticles - so it doesn't make a difference whether you have a conventional silver textile or a nano-textile - except that the nano-textile releases less silver to the environment. Nano-Ag only contributes to a small extent to the silver flow into the environment”.

He continued: “Nanotextiles do not release their silver as nanoparticles (only to a small extent) and they are not different from conventional silver-textiles.  So they do not pose a specific "nano-hazard" to the environment.”

The study – published in Environmental Science & Technology – showed most particles released were relatively large, and during the first wash.  The total released during a normal washing cycle without bleach varied from 1.3 to 35% of the fabrics total nanosilver.  It also showed that in everyday washing, bleach had no effect on the amount of silver nanoparticles released.

The study came about after Dr Nowack’s work on exposure modelling of engineered nanoparticles in the environment; he needed further information of the release of nanoparticles from products.  “We decided to start with nanotextiles as there is much expertise on textiles available in our institute,” he said, “I am to continue this work, especially to get more information on the coarse particles that were released (e.g. composition, behaviour, removal during water treatment).”

Manufacturers use silver nanoparticles because of their antibacterial action, which slows the growth of odour-causing bacteria.  Silver is used in clothing in two main forms; either as silver ions integrated into the polymer the yarn is made from, or it is coated onto the yarn.