Related by context. Frequent words. (Click for all words.) 67 tailpipe emissions 64 carbon dioxide emissions 63 emissions 63 greenhouse gas emissions 61 greenhouse gases 61 nitrogen oxide emissions 60 CO2 emissions 60 nitrogen oxides 60 greenhouse gas 60 air pollution 59 greenhouse gasses 58 nitrogen oxide 58 carbon emissions 58 pollution 57 exhaust emissions 56 greenhouse emissions 56 emission 56 greenhouse gas emission 55 Emissions 54 GHG emissions 54 carbon dioxide 54 ozone pollution 53 pollutants 53 mercury emissions 52 carbon emission 52 heat trapping gases 52 polluting 52 sulfur dioxide emissions 51 global warming gases 51 CO2 51 smog 51 particulate matter 50 emission reductions 50 reduce carbon emissions 50 NOx 50 carbon dioxide CO2 49 particulates 49 mercury pollution 49 diesel exhaust 49 pollutant 47 tailpipe 47 soot 46 tailpipes 46 GHG 46 cleaner burning 46 CARB 46 emission reduction 45 Air Quality 45 diesel 45 particle pollution 45 Air Pollution 45 diesel powered 44 ozone 44 VOCs 44 sulfur dioxide 44 burning fossil fuels 44 exhaust fumes 44 Environmental Protection Agency 44 diesel engines 44 fossil fuel 43 volatile organic compounds 43 gas guzzler 43 mpg 43 gases blamed 43 polluters 42 idling 42 Clean Air 42 cleaner fuels 42 reducing carbon emissions 42 EPA 42 toxic chemicals 42 gas guzzling 41 fossil fuels 41 Air Pollution Control 41 carbon footprint 41 regulate greenhouse gases 41 polluter 40 dirtier 40 carbon 40 diesels 40 Emission 39 pollute 39 harmful chemicals 39 particulate 39 emit 39 gas guzzlers 39 emitted 39 automobiles 39 combustion engine 38 nitrogen dioxide 38 methane 38 Pollution 38 cleaner 38 zero emission 38 combustion 38 polluting industries 37 drunken drivers 37 dirtiest 37 toxics 37 catalytic converters 37 coal fired