A group of researchers in Japan say they have found microplastics in snow across wide areas of the northern prefecture of Hokkaido, including a World Natural Heritage site.

Microplastics, which are pieces 5 millimeters or smaller, pose a threat to marine ecosystems because fish and other creatures can easily swallow them. The particles have also been found in the air near the top of Mount Fuji, Japan's highest peak.

A group led by Ohno Hiroshi, an associate professor at the Kitami Institute of Technology in Hokkaido, studied samples of newly accumulated snow from eight locations in the prefecture. The research was conducted from 2021 through February this year.

The locations include an area of small lakes surrounded by native forest in Shiretoko, the World Natural Heritage site, and also Asahidake, the highest peak in Hokkaido which is in the Daisetsuzan National Park.

The researchers detected microplastics in all eight locations.

They say the microplastics found in such remote areas were mainly made of polyethylene and measured 0.06 millimeters or less. The group believes that microplastics floating in the atmosphere got mixed with snow and accumulated across wide areas.

Ohno says microplastics were found even in areas that are less affected by human activities. He stresses that more studies should be conducted as microplastics in the snow pose a threat to ecosystems just as they do in the ocean.