Microplastics Discovered in Air at Mount Fuji Summit

Microplastics found in the air at the summit of Mount Fuji.

“When we think of microplastics, we usually think of plastic waste on land being carried to the ocean through rivers, but in fact, they are also present in the atmosphere.”

This statement comes from Professor Hiroshi Okouchi of the Faculty of Science and Engineering at Waseda University.

During his air pollution research around the Angkor ruins, he witnessed plastic waste scattered on the roadside and scenes of people digging holes to bury plastic bottles for disposal.

“Southeast Asia has high temperatures, high humidity, and strong UV rays. Plastic waste deteriorates easily, and we thought microplastics would be released into the atmosphere.”

In fact, until Professor Okouchi and his team conducted their research, there had been little study of microplastics in the atmosphere.

Professor Okouchi and his team initially conducted research at Mount Fuji’s summit, the rooftop of an 18-story research building in Shinjuku, and in Cambodia.

The atmospheric boundary layer extends up to 2 km from the ground, where atmospheric pollutants accumulate under the influence of the surface. The area from 2 km to 10 km above the ground is called the free convection zone, and Mount Fuji’s summit lies within this zone.

“While the presence of microplastics had not been confirmed in the free convection zone, we found microplastics at the summit of Mount Fuji during our research.”

In Shinjuku, there is usually about one microplastic particle per cubic meter of air, but at the summit of Mount Fuji, the number ranges from 0.01 to 0.06 particles.

“However, the concentration of microplastics in the air varies with the season and weather. When a large low-pressure system like a typhoon occurs, polypropylene increases in Shinjuku, and on clear, sunny days with a strong high-pressure system, up to seven microplastic particles per cubic meter were detected.

At the summit of Mount Fuji, when the air from Southeast Asia is brought over by a typhoon, both the concentration and variety of microplastics increase. This was a significant discovery, even in the free convection zone.”

In Cambodia’s atmospheric boundary layer, when surveyed during the rainy season of 2019, 49 microplastic particles were detected per cubic meter, but in the dry season of 2023, only 4 particles were found per cubic meter.

When a large low-pressure system like a typhoon occurs, an updraft is generated, and air from the ground rises into the free convection zone. During this time, oceanic microplastics are also lifted. In a winter survey of surface seawater off Noto, Japan, between 20,000 and 330,000 microplastic particles per cubic meter were detected.