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Web Date: July 11, 2013

Nanoparticles In Athletic Apparel May Seep Into Sweat

Nanotechnology: Some clothing may expose people to significant amounts of silver nanoparticles while they exercise
Department: Science & Technology
News Channels: Environmental SCENE, Materials SCENE, Nano SCENE
Keywords: clothing, nanoparticles, sweat, toxicology
Some garments designed to be worn during physical activity contain bacteria-killing or ultraviolet-light-blocking nanoparticles that may end up in people’s sweat.
Credit: Shutterstock
Some garments designed to be worn during physical activity contain bacteria-killing or ultraviolet-light-blocking nanoparticles that may end up in people’s sweat.
Credit: Shutterstock

For some lines of clothing, nanoparticles are the new fashion accessory. Manufacturers add the materials to clothing to prevent stinky molds from growing on sweaty socks or to protect people from the sun’s ultraviolet light. However, some toxicologists worry that the intimate contact between the clothing and skin may expose people to nanoparticles. In a new study, researchers measured how much of the materials leach off clothing into simulated sweat. (Environ. Sci. Tech. 2013, DOI: 10.1021/es304329w). They found that some pieces of clothing released significant levels of silver nanoparticles.

Two common types of nanoparticles found in clothing are titanium dioxide and silver: They’re used to make UV-resistant and antimicrobial apparel, respectively. Little is known about what effects these materials have on human health. In fact, researchers in Germany are currently conducting a large toxicological study on these particles and other nanomaterials, says Natalie von Götz of the Swiss Federal Institute of Technology (ETH), Zurich.

Besides learning about the materials’ toxicology, researchers also need to determine exposure levels under real-world conditions, von Götz says. She and her colleagues noted that people often wear nanoparticle-treated clothing during sporting or outdoor activities. So to estimate exposure levels, the team simulated the wear-and-tear a piece of clothing would undergo if worn by an active person and measured how many nanoparticles sloughed off.

The researchers studied fabric samples from garments they determined had titanium dioxide nanoparticles, silver nanoparticles, or both. This apparel included socks, shirts, and trousers. They put the samples into plastic bottles containing acrylic balls and up to 180 mL of artificial sweat, a water solution containing salts and organic molecules similar to that of human perspiration. Then, they placed the bottles into a washing machine and allowed the bottle to bounce around for at least 30 minutes. After agitating the samples, the researchers measured the concentration of nanoparticles in the artificial sweat with inductively coupled plasma optical emission spectroscopy. They also measured the sizes of the particles using scanning transmission electron microscopy.

Using that data, the team next estimated how much of the particles would end up on a person’s skin after strenuous exercise, such as playing tennis. They considered only levels of titanium dioxide and silver particles smaller than 450 nm, because larger particles are less likely to be absorbed through the skin, von Götz says. In making their exposure estimates, the reseachers also took into account a person’s gender and body weight, along with the size of the garment.

Based on these estimates and comparisons to other exposure sources of the metals, the team concluded that exposure levels for silver nanoparticles could be significant. For example, a 77-kg man wearing trousers and a T-shirt containing silver nanoparticles would receive about 1.3 mg of silver per day. Meanwhile, the exposure level from dietary supplements that contain silver is at most 0.5 mg per day. The scientists also concluded that exposure levels for titanium dioxide nanoparticles weren’t a great concern. The calculated maximum exposure level was significantly less than that of a single application of sunscreen.

Peter Lauz of the Federal Institute of Risk Assessment in Berlin thinks the researchers’ methods are a valuable way to evaluate the effects of new materials on people’s health. “We need to know what the consumer is exposed to,” he says. The method, he adds, still needs to be validated to ensure it adequately simulates physical activity and works with other types of fabrics.

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Stephen  (Fri Jul 12 11:17:42 EDT 2013)
Just how do we know if the clothing we are buying contains Nanoparticles? I have seen no info about it on the manufacture's labels attached to clothing? Thank you.
Don Milligan (Sat Jul 13 12:46:30 EDT 2013)
Unless the object is a reflex horror at anything new, remember, the method has not been validated, and the amount absorbed was not stated to be toxic. It's a good preliminary study to see if there is any reason for concern.
Alysa (Sun Jul 14 19:44:04 EDT 2013)
Stephen, usually the presence of the nanoparticles is they key selling point of the garments, and they are more expensive than run-of-the mill active wear. SmartSilver is one example of a company that uses silver nanoparticles, and they are very open about it. Their activewear website talks about the technology.

It's unlikely that you will find nanoparticles in clothing you buy unless you are actively looking for it--silver is fairly expensive, even on the nanoscale.
Stefan (Wed Jul 17 10:51:25 EDT 2013)
I don't know how much silver the clothing might contain to begin with, but if 1.3 mg/day is lost, it probably wouldn't take too long for the effectiveness to diminish significantly.
Gary  (Mon Jul 22 01:26:12 EDT 2013)
I have stopped using silver impregnated liner socks when hiking. I develop a rash around my ankles every time I use them in warm/hot weather. This does not occur with "Smart Wool",or "Cool Max" type synthetic materials. I know others who have had the same problem and solved it by not using the nanosilver brands
Alex Floyd (Thu Aug 08 15:18:46 EDT 2013)
How toxic are nano particles? The answer depends on chemical composition. I saw an article about iron oxide nano particles inhibiting white cell phagocytosis of bacteria? I suppose bacteremia could kill you.
James Graley (Sat Aug 31 17:22:23 EDT 2013)
As a cyclist, what would worry me a about silver nano-particles is the event of a crash, where torn fabric and flesh can commingle. Wool is a better choice.
Jetman (Sun Jul 26 17:54:12 EDT 2015)
Crash shouldn't be a problem. The Marine Corps adopted this technology years ago and I seem to recall seeing some peer reviewed studies recently that spoke towards the IED shredding of these clothing (when worn by the Brits) that actually sped up healing time and decreased secondary infections at a remarkable rate.
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