Related by context. Frequent words. (Click for all words.) 65 pollutants emitted 58 nitrous oxides 58 sulfur oxides 57 pollutants 56 particulates 56 sulfur dioxide SO2 56 toxic pollutants 56 particulate matter emissions 55 nitrogen oxides 55 sulfur dioxide 55 harmful pollutants 55 emitted 54 sulfur dioxide nitrogen oxide 54 nitrogen oxide 54 smokestack emissions 54 emit 53 smog forming emissions 53 soot particles 53 harmful toxins 53 particulate matter 53 carbon dioxide 53 particulate emissions 53 fine particulates 53 CO -2 53 greenhouse gases GHGs 52 airborne pollutants 52 SO2 52 sulfur dioxide nitrogen oxides 52 particulate matter PM 52 pollutant 52 harmful contaminants 52 nitrogen oxides NOx 52 Hydrogen sulfide 52 gases emitted 51 sulfur oxide 51 air pollution 51 Sulfur dioxide 51 toxic chemicals 51 carbon emitted 50 Carbon dioxide emissions 50 CO2 emitted 50 emit CO2 50 harmful chemicals 50 pollution 50 diesel exhaust 50 greenhouse gases GHG 50 ultrafine particles 50 SO2 emissions 50 particulate pollution 50 toxic byproducts 50 nitrogen oxide emissions 50 toxins 49 fine particulate 49 furans 49 particulate 49 soot 49 greenhouse gasses 49 Pollutants 49 greenhouse gases 49 VOCs 49 heat trapping carbon dioxide 49 VOC emissions 48 sulfur hexafluoride 48 carbon dioxide emitted 48 carcinogens 48 fine particle pollution 48 emissions 48 toxicants 48 volatile organic compounds 48 aerosol particles 48 pollute 48 dioxide 48 nitrous oxide emissions 48 nitrogen phosphorus 48 CO ² 48 pollutant emissions 48 potentially carcinogenic 48 carbon dioxide emissions 48 airborne particles 48 ozone smog 48 Ultraviolet light 48 methane 47 toxic substances 47 greenhouse gas 47 particulate filters 47 emitting 47 carcinogenic chemicals 47 CO2 47 GHGs 47 sulfur compounds 47 greenhouse gases emitted 47 noxious gases 47 contaminants 47 harmful gases 47 mercury pollution 47 emission 47 pollutions 46 Greenhouse gases 46 sulphates 46 carbon dioxide CO2 46 oxygenates