It was already a big problem before the Covid-19 pandemic, but plastic waste is now turning into an even larger issue – and face masks, in particular, are not helping the cause. We need them to avoid the spread of the virus but at the same time, there’s no official guidance on how to dispose of them. Most of them just end in the trash, and that needs to change.

An impressive number of face masks are used around the world, with studies estimating 129 billion are used every month. That’s good — we’re preventing a dangerous virus from spreading. But it comes at a cost. Most are made from plastic microfibers and are not properly disposed of, which means they’ll be staying in the environment for centuries to come.

In a recent commentary piece, Elvis Genbo Xu and Zhiyong Jason Ren describe waste plastics as one of the most pervasive environmental pollutants today. Before the pandemic, over 300 million tons of plastics were produced globally per year and most if ended up in nature as waste. Plastic products can’t be readily biodegraded and then fragment into microplastics and nanoplastics.

After the pandemic, it’s only gotten worse. More people are favoring plastic-packed foods — and of course, there’s the face masks.

There’s no official data on how many masks are disposed of, but with billions needed every month the figure is likely to be very high. For the researchers, disposable masks have become as problematic as plastic bottles or even worse. While 25% of the bottles can be recycled, there’s no guidance for mask recycle and most are disposed of as solid waste.

Disposable masks are usually made of three layers. The outer one is made up of a nonabsorbent material like polyester that protects against liquid splashes. The middle one is non-woven fabrics like polystyrene that prevent droplets and aerosols, while the inner one is made of an absorbent material such as cotton so to absorb vapor. Different polymers are used in manufacturing.

Once in the environment, the mask is subjected to solar radiation and heat. But the degradation can actually take a very long time because of the plastic components, the researchers argued. If they aren’t properly collected, the masks can then be transported from land into freshwater and marine ecosystems by river flows, oceanic currents and surface run-off.

“When breaking down in the environment, the mask may release more micro-sized plastics, easier and faster than bulk plastics like plastic bags. Such impacts can be worsened by a new-generation mask, nanomasks, which directly use nano-sized plastic fibers (e.g., diameter < 1 mm) and add a new source of nanoplastic pollution,” the researchers wrote in the study.

The presence of waste masks has been increasingly reported in different environments since the start of the pandemic, with posts in social media sharing images of wildlife tangled in elastic straps of masks. NGOs in Asia and Europe have collected hundreds of masks on beaches over the past few months, hoping to raise awareness through active campaigns.

For Xu and Ren, it’s urgent to launch coordinated efforts from environmental scientists, medical agencies, and solid waste managing organizations to minimize the negative impacts of disposal masks — eventually preventing it from becoming a problem too big to handle. Plastic waste is already massive and we shouldn’t add masks to that combo.

The researchers recommend a critical rethinking of the way masks are used, manufactured and disposed of. This would include carrying out a life-cycle evaluation on masks’ production and disposal, encouraging people to use washable masks and replacing single-use plastic masks. At the same time, mask-only trash cans could be set up for collection and disposal.

Researchers in Australia have already found one potential solution, developing new recycled material for building roads out of shredded face masks. The road-making material is feasible and meets civil engineering safety standards, with the plastic particles adding stiffness and strength to the final product when used in the base layer for roads and pavements.

The comment piece was published in the journal Frontiers of Environmental Science & Engineering.