Snowmobiles are not culprits in regards to the copulation of air pollutants that is prevalent in gas consuming automobiles. Snowmobiles are driven mostly on snow that does not require a lot of pollutants causing substances such as ethanol. Therefore snowmobiles are not a threat to the environment or to pollution.
Snowmobiles do product air pollution, that can not be denied. However, they do not produce a significant amount of air pollution to cause them to be banned. If you ban snow mobiles for air pollution then you would need to ban other sources of air pollution that cause as much or more pollution than snow mobiles, which would include several corporations. It does not make sense to ban snowmobiles.