Industrial point sources
If not effectively controlled, emissions from industry can place health and amenity at risk, not only at the neighbourhood level, but more generally at the airshed level. During the past 30 or so years, state and territory environment protection agencies (working together with local government) have successfully employed a range of measures (both regulatory and nonregulatory) to greatly reduce the threat from industrial sources. As a result, apart from in major industrial centres or smaller centres with one or two significant industrial sources, diffuse sources (motor vehicles and commercial and domestic sources) tend to be the more important threats to urban air quality at an airshed scale.
A possible exception to this generalisation is the potential impact on urban air quality that could accompany any significant increase in local generation of electricity using cogeneration (i.e. combined heat and power) facilities. As noted by the Victorian Environment Protection Authority:
… cogeneration facilities can yield significant greenhouse emissions reduction benefits, but may pose a potential threat to air quality, as the burning of natural gas releases significant amounts of NOx. Air quality considerations will therefore be taken into account where cogeneration facilities are proposed in urban areas.203