New MIT study calculates the waste generated by N95 usage and suggests ways to reduce it.
Anne
Trafton | MIT News Office
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| British tabloids recently featured Jemima Hambro's wedding dress made from 1500 recycled face masks. (David Parry/PA) |
All of those masks carry both financial and environmental costs. The Covid-19 pandemic is estimated to generate up to 7,200 tons of medical waste every day, much of which is disposable masks.
And even as the pandemic slows down in some
parts of the world, health care workers are expected to continue wearing masks
most of the time.
That toll could be dramatically cut by adopting reusable masks, according to a new study from MIT that has calculated the financial and environmental cost of several different mask usage scenarios.
Decontaminating regular N95 masks so
that health care workers can wear them for more than one day drops costs and
environmental waste by at least 75 percent, compared to using a new mask for
every encounter with a patient.
“Perhaps unsurprisingly, the approaches that incorporate reusable aspects stand to have not only the greatest cost savings, but also significant reduction in waste,” says Giovanni Traverso, an MIT assistant professor of mechanical engineering, a gastroenterologist at Brigham and Women’s Hospital, and the senior author of the study.
The
study also found that fully reusable silicone N95 masks could offer an even
greater reduction in waste. Traverso and his colleagues are now working on
developing such masks, which are not yet commercially available.
Jacqueline
Chu, a physician at Massachusetts General Hospital, is the lead author of the
study, which appears in the British Medical Journal Open.
Reduce
and reuse
In the early stages of the Covid-19 pandemic, N95 masks were in short supply. At many hospitals, health care workers were forced to wear one mask for a full day, instead of switching to a new one for each patient they saw.
Later on,
some hospitals, including MGH and Brigham and Women’s Hospital in Boston, began
using decontamination systems that use hydrogen peroxide vapor to sterilize
masks. This allows one mask to be worn for a few days.
Last
year, Traverso and his colleagues began developing a
reusable N95 mask that is made of silicone rubber and contains
an N95 filter that can be either discarded or sterilized after use. The masks
are designed so they can be sterilized with heat or bleach and reused many
times.
“Our vision was that if we had a reusable system, we could reduce the cost,” Traverso says.
“The majority of disposable masks also have a significant
environmental impact, and they take a very long time to degrade. During a
pandemic, there’s a priority to protect people from the virus, and certainly
that remains a priority, but for the longer term, we have to catch up and do
the right thing, and strongly consider and minimize the potential negative
impact on the environment.”
Throughout the pandemic, hospitals in the United States have been using different mask strategies, based on availability of N95 masks and access to decontamination systems.
The MIT team decided to model the impacts of several different
scenarios, which encompassed usage patterns before and during the pandemic,
including: one N95 mask per patient encounter; one N95 mask per day; reuse of
N95 masks using ultraviolet decontamination; reuse of N95 masks using hydrogen
peroxide sterilization; and one surgical mask per day.
They
also modeled the potential cost and waste generated by the reusable silicone
mask that they are now developing, which could be used with either disposable
or reusable N95 filters.
According
to their analysis, if every health care worker in the United States used a new
N95 mask for each patient they encountered during the first six months of the
pandemic, the total number of masks required would be about 7.4 billion, at a
cost of $6.4 billion. This would lead to 84 million kilograms of waste (the
equivalent of 252 Boeing 747 airplanes).
They
also found that any of the reusable mask strategies would lead to a significant
reduction in cost and in waste generated. If each health care worker were able
to reuse N95 masks that were decontaminated with hydrogen peroxide or
ultraviolet light, costs would drop to $1.4 billion to $1.7 billion over six
months, and 13 million to 18 million kilograms of waste would result (the
equivalent of 39 to 56 747s).
Those
numbers could potentially be reduced even further with a reusable, silicone N95
mask, especially if the filters were also reusable. The researchers estimated
that over six months, this type of mask could reduce costs to $831 million
and waste to 1.6 million kilograms (about five 747s).
“Masks
are here to stay for the foreseeable future, so it’s critical that we
incorporate sustainability into their use, as well as the use of other
disposable personal protective equipment that contribute to medical waste,” Chu
says.
Environmental
burden
The
data the researchers used for this study were gathered during the first six
months of the pandemic in the United States (late March 2020 to late September
2020). Their calculations are based on the total number of health care workers
in the United States, the number of Covid-19 patients at the time, and the
length of hospital stay per patient, among other factors. Their calculations do
not include any data on mask usage by the general public.
“Our
focus here was on health care workers, so it’s likely an underrepresentation of
the total cost and environmental burden,” Traverso notes.
While
vaccination has helped to reduce the spread of Covid-19, Traverso believes
health care workers will likely continue to wear masks for the foreseeable
future, to protect against not only Covid-19 but also other respiratory
diseases such as influenza.
He and others have started a company called Teal Bio that is now working on further refining and testing their reusable silicone mask and developing methods for mass manufacturing it. They plan to seek regulatory approval for the mask later this year.
While cost and environmental impact are
important factors to consider, the effectiveness of the masks also needs to be
a priority, Traverso says.
“Ultimately,
we want the systems to protect us, so it’s important to appreciate whether the
decontamination system is compromising the filtering capacity or not,” he says.
“Whatever you’re using, you want to make sure you’re using something that’s
going to protect you and others.”
The research was funded by the MIT Undergraduate Research Opportunities Program, the National Institutes of Health, and MIT’s Department of Mechanical Engineering.
