"Plastic rain" is now a real thing as airborne microplastics are discovered in clouds

The presence of plastic in oceans and terrestrial environments has long been a concern for environmentalists. Now, a study from Waseda University reveals that the problem extends far beyond solid ground and deep waters. Airborne microplastics (AMPs), which are minute plastic particles less than 5mm in size, may have now become an integral component of clouds. This can lead to what is known as “plastic rainfall.”

Understanding microplastics

Microplastics form from the degradation of larger plastic waste or are released from industrial effluents. 

Alarmingly, these tiny particles are known to enter the bodies of humans and animals, with research detecting their presence in several organs including the lung, heart, blood, placenta, and even feces. 

Approximately ten million tons of microplastics end up in oceans annually. From here, they are released into the atmosphere, potentially influencing the composition of clouds.

Free troposphere 

“The free troposphere is an important pathway for the long-range transport of air pollutants owing to strong wind speeds; it has been observed that airborne microplastics are also transported in the free troposphere and contribute to global pollution,” wrote the study authors. 

“In addition, airborne microplastics may act as cloud condensation nuclei and ice nucleus particles during transport in the free troposphere and atmospheric boundary layer, thereby potentially promoting cloud formation.”

Studying airborne microplastics

The experts investigated the role of airborne microplastics in the biosphere, focusing on their potential impacts on human health and the climate. 

“Microplastics in the free troposphere are transported and contribute to global pollution. If the issue of ‘plastic air pollution’ is not addressed proactively, climate change and ecological risks may become a reality, causing irreversible and serious environmental damage in the future,” said study co-author Hiroshi Okochi.

How the research was conducted 

To better understand the influence of airborne microplastics on the atmosphere, Okochi’s team collected cloud water from several regions with varying altitudes. The collection sites included the summit of Mount Fuji, its southeastern foothills, and the summit of Mt. Oyama.

Using advanced imaging techniques, the team identified the presence of microplastics in the cloud water and further analyzed their physical and chemical properties. 

Alarmingly, the team detected nine distinct types of polymers and a form of rubber.

Furthermore, these airborne microplastics were found to play a crucial role in rapid cloud formation, which could have wider implications for the global climate.

Ecological and climate impacts

The accumulation of airborne microplastics, especially in polar regions, might severely disrupt the planet’s ecological balance and lead to a dramatic loss of biodiversity. 

“AMPs are degraded much faster in the upper atmosphere than on the ground due to strong ultraviolet radiation, and this degradation releases greenhouse gases and contributes to global warming,” said Okochi.

“As a result, the findings of this study can be used to account for the effects of AMPs in future global warming projections.”

Okochi collaborated with study lead author Yize Wang, also from Waseda University, and Yasuhiro Niida of PerkinElmer Japan Co. Ltd.

The research is published in the journal Environmental Chemistry Letters.

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