Zheng Wang and Chunjiang An from Concordia University are studying how environmental weathering deteriorates discarded disposable masks and pollutes our waterways.

The enormous surge of face mask use since the beginning of the global lockdown in March 2020 has saved countless human lives, a crucial component to limiting the transmission of the novel coronavirus. But with 129 billion masks being consumed globally every month, disposal has become a major issue with implications on human, animal, and ecological health.

The problem becomes more acute as, according to a recent study by Concordia researchers, a single mask left exposed under natural conditions can release more than 1.5 million microplastics into the aqueous environment.

In a new paper, PhD student Zheng Wang and Assistant Professor Chunjiang An investigated how disposable masks break down in a shoreline environment and the environmental implications that poses. They examined changes in chemical composition and strength degradation of the three different mask layers caused by UV exposure and sand abrasion.

Shorelines, they write, are not only the main receptors of discarded masks; their unique environment also leads to further breakdown of masks into plastic particles.

The study was published in the Journal of Hazardous Materials. It was co-authored by Xiujuan Chen of the University of Regina, Kenneth Lee of Fisheries and Oceans Canada (Wang’s co-supervisor), Baiyu Zhang of Memorial University and Concordia PhD student Qi Feng.

36 hours to break down

The researchers simulated shoreline environment conditions on a set of masks and created a control group with which to compare. The experimental masks were placed in an uncovered Petri dish and exposed to UV lights between one and 48 hours. Control samples were wrapped in aluminum foil and exposed under the same conditions.

They then separated the masks by layer—outer, middle, and inner—and irradiation times, and placed them in flasks to test and control for the presence of sand. The strips were then analyzed using a scanning electron microscope and an atomic force microscope. The researchers also examined particle size distribution in a water sample using a LISST-200X particle size analyser.

Pictured: Zheng Wang. Image Credit: Concordia University.

After 18 hours of weathering, the outer and inner layer of the masks exhibited noticeable damage to their fibre surfaces. Damage to the fibres in the middle layer, however, which are six times smaller than those in the outer and inner layers, was more severe: the surfaces had become abrasive, and fracturing had occurred. After 36 hours of exposure to UV rays, fibres in all three layers had fractured. This created miniscule fibre fragments. In addition to this, particles started attaching themselves to the fibres. Their surfaces showed obvious signs of weathering, including cracks, flakes, grooves, and pits. Damage was most severe in the middle layer, where all the fibres had broken into small fragments.

These findings coincided with an observed increase in the number of microparticles released into the water after 18 hours of weathering. After 36 hours, the researchers observed the broken mask fibres easily entering the water, even to the naked eye, and millions of small particles existed in the sample water.

SEM image of mask fibers after weathering. Image Credit: Zheng Wang.

Local solutions possible

The results tell Wang and An that urgent action is needed to securely dispose of the billions of masks being used worldwide every month.

“We need to increase our environmental awareness and reduce abandoned masks in the environment,” said Wang. “Our governments and industries also need to improve the existing waste management practices and manufacture masks with less environmental impact.”

On an immediate, practical level, An suggests simply adding more dedicated mask bins for public use on places like university campuses. This would would help the collection of used masks and prevent abandoned masks from entering the natural environment.

A copy of the paper is available here.


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