Is oxygen a pollutant? If not, then carbon dioxide cannot be a pollutant as well. Oxygen is produced by plants. To thrive plants need water, soil, nutrients, sunlight and carbon dioxide. Some would suggest we need to reduce the carbon dioxide (plant food) in the air. Some say greenhouse gasses are bad. Yes, carbon dioxide is a greenhouse gas, but are greenhouse gasses bad? Do we really know what the ideal amount of carbon dioxide should be in the air?