Related by context. Frequent words. (Click for all words.) 66 carbon dioxide emissions 66 nitrogen oxide 65 nitrogen oxides 65 carbon dioxide 64 greenhouse gases 64 nitrogen oxide emissions 63 greenhouse gasses 63 tailpipe emissions 63 greenhouse gas emissions 63 CO2 emissions 63 emissions 62 GHGs 62 greenhouse gas 62 carbon dioxide emitted 61 pollutants 60 carbon dioxide CO2 60 air pollution 60 carbon emissions 60 CO2 59 carbon dioxide CO2 emissions 59 carbon dioxide emission 59 exhaust emissions 59 pollution 58 particulate pollution 58 pollutant 58 greenhouse emissions 57 GHG emissions 57 particulate matter 57 emission 56 diesel exhaust 56 greenhouse gas GHG emissions 56 sulfur dioxide emissions 56 mercury emissions 56 sulfur dioxide 55 NOx 55 reduce carbon emissions 55 greenhouse gas emission 55 Emissions 54 CO2 emission 54 particulates 54 polluting 54 volatile organic compounds 53 cleaner burning 52 global warming gases 52 reducing carbon emissions 52 Carbon dioxide 52 emission reductions 52 ozone pollution 52 exhaust fumes 52 fossil fuel 52 SO2 51 VOCs 51 smog 51 GHG 51 burning fossil fuels 51 carbon emission 51 heat trapping gases 51 toxic chemicals 51 Carbon Dioxide 50 mercury pollution 50 emission reduction 50 reducing CO2 emissions 50 emitted 49 fossil fuels 49 soot 49 carbon emitting 49 water vapor 49 fine particulate matter 49 tailpipe 48 Environmental Protection Agency 48 ozone 48 methane 48 diesel powered 48 tailpipes 48 emit 47 carbon footprint 47 heat trapping 47 internal combustion engines 47 combustion 47 regulate greenhouse gases 47 emitting 47 EPA 47 diesel engines 47 reduce greenhouse gas 47 diesel 46 Clean Air 46 gas guzzling 46 wood stoves 46 heat trapping greenhouse gases 46 acid rain 46 exhaust gases 46 environmentally harmful 46 particle pollution 46 nitrogen dioxide 46 particulate 46 emits 45 AQMD 45 harmful chemicals 45 mercury 45 idling 45 combustion engine