At a glance
The frequency, duration and severity of episodes of poor air quality in urban centres are influenced by short-term meteorological conditions, in combination with local topography and/or atypical emissions. Air quality is usually restored to acceptable levels once the immediate conditions change, either through a change in the wind, cessation of the emissions, rain or dispersion of the pollutant. Therefore, our urban airsheds may be considered highly resilient, in terms of the common dictionary definition of the word. However, human resilience to the effects of prolonged or recurring exposure to air pollutants is limited.
Resilience is the environment’s capacity to return to a previous state if the system's state has been significantly affected by a disturbance. Australia’s metropolitan cities all experience episodes of poor air quality (measured in terms of particulate pollution, or pollution by ozone and its precursors NOx and VOCs). The frequency, duration and severity of these episodes are strongly influenced by short-term meteorological conditions (principally temperature and wind conditions), in combination with local topography, as well as atypical events such as dust storms, bushfire smoke or accidental releases, such as from factory fires or chemical spills. Air quality is usually restored to acceptable levels once the immediate conditions change, either through a change in the wind, cessation of the emissions or dispersion of the pollutant. In this context, our major urban airsheds are highly resilient.
In addition to the resilience of the atmosphere, it is also important to consider resilience from the perspective of the humans who cause most air pollution and who are affected by it. People have limited resilience in the face of prolonged or recurring exposure to air pollutants (see Health impacts of air pollution). Individuals vary in their sensitivity to exposure to particular air pollutants, with those most sensitive accounting for the great majority of the observed deaths and illness attributed to poor air quality.
Unfortunately, our capacity to adapt to unacceptably high levels of air pollution is inherently limited. We can leave the affected area, shelter indoors (of limited value without effective air filtering), avoid strenuous exercise, wear face masks and, in the case of asthmatics and others with respiratory ailments, take prescribed medicines. However, these strategies are only effective if the pollution is present in a particular area or for a particular time. These short-term adaptive strategies are not substitutes for action to mitigate the pollution at source through a range of regulatory and nonregulatory measures.