Researchers sought to quell concerns that microplastics from disposable masks could cause lung damage, saying their study did not show that simply wearing masks and breathing through them is potentially harmful.

"It is not the wearing of the mask itself that causes lung damage, but the microplastics that remain after disposing of the mask," said Yoo Byung-ah, an official at the Korea Institute of Toxicology. "Microplastics cannot be inhaled in one's lungs just by wearing and breathing through a mask."

Yoo was countering claims raised in response to the institute's own report about a study into the impact of microplastics from disposable masks on animals.

The study did not measure real-world impacts of mask-wearing. Instead, researchers dropped microscopic particles of polypropylene -- a main material in masks -- into the airways of animals. This caused inflammation and damage in their lungs, according to the KIT report.

But disposable masks need to be exposed to humidity and ultraviolet rays for decades before they start to break down into microplastics, Yoo said.

Lee Kyu-hong, the head of the inhalation toxicity research team under the KIT who conducted the study, said the study was aimed at analyzing the impact of disposed masks and plastic products on humans and nature in the future, rather than the risks of wearing masks.

"Right now, people are inhaling microplastics that were discarded in the past," Lee said. "We need to consider the future impact of the tremendous increase in plastic use during this COVID-19 pandemic period."