SEARCH Articles Figures Tables Air pollutants primary Ammonia primary pollutant Carbon dioxide primary pollutant Carbon monoxide primary pollutant Dioxin primary pollutant Hydrocarbons primary pollutant Hydrogen chloride primary pollutant Hydrogen sulfide primary pollutant London smog - primary pollution Nitric oxide primary pollutant Pollutant primary sources Pollution sources primary pollutants Primary and Secondary Pollutants Primary pollution prevention Primary toxic pollutants Sulfur Dioxide A Major Primary Pollutant Sulfur dioxide primary pollutant