You Can Wash and Reuse Your Cloth Mask for a Year Without Losing Protection, Study Finds

There is growing concern about how the single-use Personal Protective Equipment (PPE) that we have all begun wearing in the wake of the coronavirus pandemic may add to plastic pollution already plaguing our environment.

Now, there is good news for anyone hoping to protect themselves sustainably with a cloth mask. A new study published in Aerosol and Air Quality Research has found that a reusable cotton mask can go through a year of washes without losing its efficacy.

“This is good news for the environment because a reusable mask is likely to be more sustainable than a disposable one,” study co-author and University of Colorado Boulder assistant professor Marina Vance told EcoWatch in an email.

A Year’s Worth of Washes

To test the efficacy of cloth masks over time, Vance and her team replicated the process of washing two-layer cotton fabric sample coupons once a week for a year, or 52 times.

“Our colleagues at the National Renewable Energy Laboratory (NREL) prepared double-layered cloth coupons and performed sequential washing and drying cycles in a controlled manner, using commercial equipment,” Vance explained.

Every seven washes, the researchers then tested how well the masks could filter out particles. They did this by attaching the coupons to the end of a steel funnel and controlling the flow of air and particles through the opening, a University of Colorado Boulder press release detailed. They tried to replicate real life conditions by testing the coupons under high heat and humidity conditions similar to human breathing.

“Our laboratory tested the filtration efficiency and inhalation resistance of all samples and found that, even after many washes, the filtration efficiency did not improve or deteriorate,” Vance said. “It remained roughly the same. The inhalation resistance increased slightly, which means that the material lost some of its breathability, but not enough to impact its usefulness.”

Vance said the results should apply to any mask made from cotton.

A New Threat

The results come amidst an increasing awareness that single-use PPE is a new and harmful category of litter.

Since the pandemic began, around 7,200 tons of medical waste has been generated every day, the press release noted, much of that disposable face masks. Another study found that, since the pandemic began, nearly three million face masks have been used per minute.

Researchers and environmental advocates have already observed these items joining the rest of the pollution littering our parks and beaches. Ocean Conservancy volunteers documented and collected 107,219 pieces of PPE from July 2020 to January 2021. Further, 94 percent of volunteers said they saw PPE while on a litter clean-up and 50 percent said they saw PPE litter on a daily basis.

There is also already evidence that this new pollution is hurting wildlife. A Dutch research team published the first scientific account of animals being impacted by PPE in March of 2021, and continues to document new instances on a website. The researchers observed a fish caught in a plastic glove and found face masks woven into birds’ nests. They also reported cases around the world of animals becoming entangled or trapped in PPE or mistaking it for food.

“We signal COVID-19 litter as a new threat to animal life as the materials designed to keep us safe are actually harming animals around us,” the study authors wrote.

In addition, PPE such as disposable masks can contribute to the problem of microplastic pollution. Ocean Conservancy further observed that a single mask could release as many as 173,000 plastic microfibers into the environment.

What Mask Should I Wear?

All of this new evidence has led some to recommend avoiding disposable PPE.

“To minimize the amount of COVID-19 litter and its effect on nature, we urge that, when possible, reusable alternatives are used,” the authors behind the Dutch study advised. “People may suffer from the coronavirus pandemic, but nature is getting sick of our plastic.”

In this context, finding out that reusable cotton masks hold up after a year of washing is good news. However, the most recent study also tested the effectiveness of several mask alternatives for filtering out particles of 0.3 microns, which is the size that the coronavirus can travel on. As Vance explained to EcoWatch:

The reason we test for particles down to and below 300 nm in diameter is because that particle size range is where most filters (masks or others) are least effective. This is due to physical reasons. We make sure to cover all sizes, including this size range. This size range is also known as the “most penetrating particle size range.” The choice of testing at the 300 nm size range has nothing to do with the coronavirus. The virus can travel on particles of that size or larger and it’s more likely to travel on larger particles or droplets.

The study found that N95 and KN95 respirators could filter out 83 to 99 percent of 0.3 micron particles on average and surgical masks could filter out 42 to 88 percent of them, but cloth masks could only filter out 16 to 23 percent and bandannas only 9 percent.

Vance advised balancing sustainability and personal health by making situation-based mask decisions.

“My recommendation is to consider layering up a cloth plus surgical mask if you think you will be in a higher risk situation and simply using a cloth mask if you think that you are in a lower-risk situation,” she said.

If you do use disposable masks, there are still steps you can take to protect wildlife, the authors of the Dutch study noted, such as cutting the ear straps before throwing them away.

Editor’s note: This story has been updated to include a statement by professor Marina Vance clarifying the testing process.