Air pollutants: gases and particulate material added to the atmosphere that can affect climate/harm people/organisms. Wind sweeping dust brings nutrients/fungal and bacterial spores, wind erosion. Volcanic eruptions releases particulate matter, sulphur dioxide and other gases (aerosols) Point source: specific spot where large quantities of pollutants are discharged. Non-point source: more diffuse, consisting of many small sources. May do harm directly or they may induce chemical reactions that produce harmful compounds. Primary pollutants: soot and carbon monoxide, pollutants emitted into the troposphere in a form that can be directly harmful or that can react to form harmful substances react with secondary. Cleaner-burning motor vehicle engines and automotive technologies (e. g. catalytic converters) Precipitators and scrubbers (chemically convert/physically remove airborne pollutants before they are emitted from smokestacks) Smog/industrial smog: when coal or oil is burned, some portion is completely combusted, forming co2, some producing co, and some remains unburned and is released as soot or particles of carbon.