To carry out the study, scientists collected cloud water from the summits of Japan’s mountains at 1,300-3,700 metres.
The first sample site was Mount Fuji, Japan’s biggest mountain. Its summit reaches an area called the free troposphere, which is the lowest layer of Earth’s atmosphere.
The free troposphere contains 75 percent of the total mass of the planetary atmosphere and 99 percent of the total mass of water vapour and aerosols. It is also where most weather phenomena occur.
Meanwhile, Mount Ōyama’s summit lies in the atmospheric boundary layer, within the lowest section of Earth’s atmosphere.
In both of these samples, the scientists found microplastics containing nine different types of polymers and one type of rubber. The clouds contained as many as 14 pieces of plastic per litre of water, ranging in size from around 7 to 95 micrometres – slightly over the average width of a human hair.
The scientists note that after prolonged exposure to ultraviolet light, plastics become hydrophilic. This means they hang around in water more easily.
An abundance of these polymers in some samples suggests they may have acted as ‘condensation nuclei’, which are tiny particles in the air on which water vapour condenses.
Condensation nuclei are the building blocks for making clouds, fog, haze, rain, and other forms of precipitation. In this sense, it’s possible that microplastics in the atmosphere are capable of influencing or disrupting weather patterns.
The report writes, ‘Overall, our findings suggest that high-altitude microplastics could influence cloud formation and, in turn, might modify the climate.’
The lead author of the research, Hiroshi Okochi of Waseda University said, ‘Microplastics in the free troposphere are transported and contribute to global pollution.’
Studies have shown that atmospheric pollution and other microplastics can be sent skyward through ocean sea spray and other aerosolization processes, which makes these particles light enough to be carried in the air.
Okochi warns that without addressing plastic air pollution proactively, worsened climate change and further ecological risks could become a reality, ‘causing irreversible and serious environmental damage in the future.’