The team identified nine different types of polymers and one type of rubber in the airborne microplastics -- ranging in size from 7.1 to 94.6 micrometers. Each liter of cloud water contained between 6.7 to 13.9 pieces of the plastics. What's more, "hydrophilic" or water-loving polymers were abundant, suggesting the particles play a significant role in rapid cloud formation and thus climate systems. "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," lead author Hiroshi Okochi of Waseda University warned in a statement Wednesday. When microplastics reach the upper atmosphere and are exposed to ultraviolet radiation from sunlight, they degrade, contributing to greenhouse gasses, added Okochi.