I haven’t read about gaseous forms of plastics in the air specifically, so it’s probably not as much of a major problem as the larger greenhouse gasses, like yes, chemicals that have many more “springy balls” like Methane that are being released as the climate warms, increasing the rate at which the globe heats. The permafrost and arctic ice has massive amounts of trapped methane that is currently being released in large explosions turning areas of the arctic circle into moonscapes of craters.