Well I first surprised by the question of yours. YES PlANTS do pollute the air(atmosphere).But they(tree) don't do pollutions by their own,New research suggests that a trees play a more complicated role in air pollution than previously thought; Trees and plants release more than just oxygen into the atmosphere as a result of photosynthesis. They also release a variety of gases, in that such gases VOC (volatile organic compounds) is the one contribute to air pollution. As I said earlier this gas or pollution VOC won't affect directly where it mixses with tailpipe(industry, auto mobile) gas to change the composition and make-up of chemicals in the VOC for the worse.where calling it TREE POLLUTION is a over statement. VOC gas emissions for trees is natural process unless or until we reduce our corben emissions VOC will add up. //coming back to your question . where as all tree do exit VOC gas but the significant leave on putting them on a text ranking is still under research so as for as I know sweet gum, oaks, coconut, ect are polluting the air.//