How Does Plastic Cause Air Pollution?

There are many factors that contribute to air pollution: the burning of fossil fuels, the release of chemical pesticides, and now plastic pollution. But how does plastic cause air pollution?
Industrial Plastic Production Raises Safety, Pollution Concerns

A number of serious accidents at plastic manufacturing plants – most recently in the Houston area — have threatened communities and contaminated the environment, bringing into question whether or not the plants’ ends justify their means: