Are Nanoparticles in Fabric Harmful?

#EcoAdvice from our expert

Dear Dr. Donley,

I was online looking at buying a face mask — since, you know, this is the world we live in now — and I found some masks that claim to have antimicrobial properties. I’m wondering what these masks are treated with and if they’re safe?

Signed,

Are these cough-y filters out of kilter?

Dear Fellow Mask-wearer,

For the past decade or so, use of antimicrobials in common fabrics has been ramping up. There’s no better example than my last trip to the store to buy undies. As I picked up a package — asking myself, “Is today the day I finally make the leap from boxers to boxer briefs?” — I noticed a little logo claiming the underwear had odor-protection properties. Curious, I checked out all the different packages I could find: About half of them touted reduced odor or antimicrobial properties. (By that time I’d spent way too much time in the underwear aisle and started to creep even myself out.)

So what are these antimicrobials that are increasingly in our underwear, socks, T-shirts and now pandemic masks? Often they’re nanoparticles of metals that have antiseptic properties, such as silver and copper. These tiny particles can be attached to fibers that are woven into fabrics and prevent the growth of bacteria that cause odors we don’t like. Nanoparticles have been around for a while but have only recently began to be widely used in everyday fabrics.

For hard-to-wash things that will be subject to conditions that promote microbial growth, or for fabrics that need to be completely sanitary, like wound dressings, there’s a solid argument that nanoparticles can be very useful. But their recent ubiquity is mostly a sales gimmick.

For fabrics that can be easily and frequently washed, antimicrobial treatments are not only pointless but come with serious environmental impacts. Metals like silver and copper are extremely harmful to aquatic organisms at extremely low levels.

The more these fabrics are washed, the more copper and silver will leach out of them into your wastewater. From there they either end up in the biosolids that are commonly sprayed as fertilizer on agricultural land or in our rivers, lakes and streams, where the harms can be even more serious. The more widely these fabrics are adopted through clever marketing ploys, the more silver and copper nanoparticles will end up in our waterways.

In a recent analysis, the Environmental Protection Agency even found that washing fabrics containing the antimicrobial cuprous iodide can result in copper levels in nearby waterways that are harmful to federally protected aquatic invertebrates for 72 days out of the year (full disclosure, my organization has sued the EPA for not taking into account these effects when approving cuprous iodide for fabric treatment). And that’s assuming that 84% of the copper is filtered out of the wastewater, which is a generous assumption: how much gets filtered out varies widely depending on the water treatment plant. Studies have shown that even a tiny increase in copper levels can impair salmon feeding, migration, spawning and ability to avoid predators.

The most important thing for you to know is that the antimicrobial properties being advertised for face masks are only proven to be effective against bacteria, not viruses. So don’t be duped into thinking the antimicrobial label means you’ll have greater protection against COVID-19 than you would from a regular old cloth mask.

Can these masks actually harm your health? We don’t really know. There’s precious little data on how many of these particles dislodge during respiration and how absorption through your lungs can affect your health. Use in masks was never really envisioned when these fabric treatments were approved, so — as with most chemical use in the United States — you may as well answer that question by flipping a coin.

Personally, I’d either make my own mask or buy one that doesn’t contain unnecessary and potentially dangerous nanoparticles. Just throw your mask in with the rest of your laundry when you can’t stand to look at the pile any longer.

And, more generally, keep an eye out when you’re buying new clothes. Some articles of clothing are unnecessarily treated with substances that will be actively washed out of them throughout their lifespan — and into waters we depend on. This gimmick is often touted as a “technology,” aimed at making you believe your clothes are an amazing, precision product of scientific ingenuity, when really it’s just a solution in search of a problem.

Don’t buy into the hype: Just wash your clothes and masks when they’re dirty and start to stink. Pretty darn simple.

Stay wild — and thank you for wearing a mask.

Dr. Donley

Dr. Nathan Donley is a scientist at the Center for Biological Diversity who answers questions about how environmental toxins affect people, wildlife and the environment. Send him your questions at AskDrDonley@biologicaldiversity.org

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