A new study finds that silver nanoparticles used to keep clothes from smelling don’t remain long enough to work.
The next time you reach for that anti-odor shirt, consider the findings of a new study published in the journal Environmental Science & Technology. Swiss researchers tested a bunch of clothes that contained silver nanoparticles, metal particles shrunk down to sizes one-billionth of one meter thin, put there to prevent odor-causing bacteria from proliferating while you sweat. They found that a large proportion of the treatments in some of these antibacterial products came out in the wash after only two launderings—wasting your money, and releasing a material into rivers and streams that's toxic to fish and other aquatic life.
Swiss researchers tested nine commercially available textiles, made from cotton, polyester, nylon, Spandex, and other synthetics, that contained silver nanoparticles. Some of the fabrics were washed in detergent alone, others in detergent and bleach, after which the scientists analyzed the wastewater to see how much of the nano-scale silver had migrated out of the clothing. Four of the fabrics lost between 20 and 35 percent of their silver nanoparticles after two washes, but one fabric lost more than half. Fabric that was washed in both detergent and bleach released fewer silver nanoparticles than fabric washed in detergent alone, but, the authors suspect, those results may be skewed by the fact that the chemical reaction between silver, bleach, and detergents may have masked the amount of silver released from the clothing.
What It Means
All that money you’re spending on fancy “anti-odor” and “antimicrobial” workout clothes could be washing down the drain, quite literally. In a previous study, researchers at Arizona State found that nano-silver-treated socks had the same problem. They found that an average of half the nanoparticles embedded in the fabric floated away with the wash water.
Silver has been used for centuries as an antibacterial agent in surgical dressings and for other medical uses, and nanoparticles of silver are the most widely used form of nanotechnology in use today, says Todd Kuiken, PhD, research associate at the Project on Emerging Nanotechnologies (PEN). “Silver’s antimicrobial property is one that suits a lot of different products, and companies pretty much run the gamut of how many consumer products they put it in.” PEN's database of consumer products that contain nanoparticles lists 150 different articles of clothing, mostly athletic clothes, socks, and gloves, that are treated with nano-silver because it kills the bacteria that cause odor. But, as this study suggests, the price you’re paying for this miraculous technology could be totally unjustified if most of it is getting washed away.
The next time you’re tempted to buy clothing labeled as “antibacterial,” “antimicrobial,” or “anti-odor,” pass it by. Even if it’s not treated with silver nanoparticles (which aren’t known to be harmful to humans but are highly toxic to aquatic organisms), it could be treated with an even more hazardous material, triclosan, a chemical that may lead to antibiotic resistance in humans and can react with water and sunlight to form the cancer-causing chemical dioxin. And who wants to be inhaling that while you’re trying to exercise?