Related by context. Frequent words. (Click for all words.) 57 pollutants 57 pollutants emitted 57 nitrous oxides 55 pollution 55 pollutions 55 Hydrogen sulfide 54 greenhouse gases GHGs 54 harmful toxins 54 polution 53 harmful contaminants 53 soot particles 53 Sulfur dioxide 53 Pollutants 53 deplete oxygen 53 Particulate matter 52 harmful pollutants 52 air pollution 52 backpressure 52 particulate emissions 52 CO -2 52 odorless colorless gas 52 Gamma rays 51 pollutant 51 incomplete combustion 51 sulfur dioxide nitrogen oxides 51 sulfur oxide 51 nitrogen oxides NOx 51 Carbon dioxide emissions 51 toxic pollutants 50 particulate matter emissions 50 toxic gases 50 particulate filters 50 Toxic chemicals 50 toxic byproducts 50 toxicants 49 emmissions 49 toxins 49 carbon dioxide 49 sulfur dioxide nitrogen oxide 49 particulates 49 potent neurotoxin 49 NOx emissions 49 EMFs 49 ultraviolet UV light 49 gases emitted 49 oxidizers 49 exhaust emissions 49 harmful gases 49 airborne pollutants 49 ionizing 49 SO2 emissions 48 poisonous carbon monoxide 48 sulfur dioxide SO2 48 combustion 48 Algae blooms 48 toxic vapors 48 UVA radiation 48 poisonous fumes 48 co2 48 greenhouse gases GHG 48 radioactive substances 48 blowholes 48 ionised 48 Carbon dioxide 48 dioxide 48 Saturated fats 48 CO ² 48 particulate pollution 48 Ultraviolet light 48 mercury pollution 48 airborne toxins 48 particulate matter 47 carbon dioxide CO2 47 sulfur hexafluoride 47 chloride ions 47 aggravate asthma 47 greenhouse gasses 47 fine particulates 47 harmful 47 ionize 47 acrolein 47 particulate matter PM 47 diesel exhaust 47 Cigarette smoke 47 noxious gases 47 radioactive steam 47 dissolved solids 47 Cosmic rays 47 airflows 47 fine particle pollution 47 diesel fumes 47 endocrine disrupting chemicals 47 nitrogen oxide NOx 47 Soil erosion 47 water vapor 47 suspected carcinogen 47 respiratory irritant 47 ozone smog 47 gases 47 CO2 46 sulfur dioxide