Related by context. Frequent words. (Click for all words.) 70 carbon dioxide 66 nitrogen oxide 66 nitrogen oxides 64 carbon dioxide CO2 63 particulate matter 63 pollutants 61 methane 60 air pollution 59 particulates 59 ammonia 59 gases 59 pollutant 59 CO2 58 greenhouse gases 58 pollution 57 acid rain 57 greenhouse gas 57 mercury emissions 57 ozone 56 NOx 56 hydrogen sulfide 56 sulfur 56 emissions 55 greenhouse gasses 55 benzene 55 carbon dioxide emissions 55 water vapor 55 coal fired 54 Carbon dioxide 54 volatile organic compounds 53 soot 53 ash 53 mercury pollution 52 gasses 52 mercury 52 smog 52 VOCs 52 emission 51 particulate 51 carbon monoxide 51 Emissions 51 chlorine 51 nitrogen 51 aerosols 49 sulfuric acid 49 vapor 49 manganese 49 heat trapping gases 49 scrubbers 49 toxic chemicals 48 greenhouse gas emissions 48 emitted 48 Methane 48 GHG 48 emission reductions 48 methane gas 48 GHG emissions 48 carbon emissions 47 vapors 47 dust particles 47 ethylene 47 greenhouse emissions 46 dioxins 46 toxic fumes 46 arsenic 46 carcinogens 45 CO2 emissions 45 hydrochloric acid 45 carbon emission 45 coal 45 burning fossil fuels 45 greenhouse gas emission 45 chromium 44 nitrates 44 Clean Air 44 smokestacks 44 scrubber 44 phosphorus 44 smokestack 44 organic compounds 44 tailpipe emissions 44 Air Quality 44 tritium 44 toxins 44 hazardous chemicals 43 sulfate 43 iodine 43 radioactivity 43 hydrogen 43 CFCs 43 nitrate 43 Pollution 43 combustion 43 ultraviolet radiation 42 toxic substances 42 polluters 42 solvents 42 emission reduction 42 contaminants 42 cleaner burning 42 gaseous