Health effects of outdoor air pollution

While concentrations of individual outdoor air pollutants are generally low in Australian cities, the combined effect of the pollutants is complex and the health impacts are not restricted to the respiratory system.

The following table lists pollutants with known health effects on people with asthma.

Table 1 Pollutants with known health effects on people with asthma.

Pollutant group  (primary sources) Known health effects Other factors contributing to effects Airborne particles (Combustion of fossil fuel and organic matter, tobacco smoke and exhaust fumes)   Respiratory tract irritation and infection, allergies Bronchitis, eye irritation Exacerbation of respiratory and cardiopulmonary diseases Asthma requiring hospital admission Lung cancer   Sulphur dioxide, sulphuric acid, heat and humidity Smoking Sulphur dioxide (and acid aerosols that form when sulphur dioxide reacts with moisture in air) (Fossil fuel combustion)   Respiratory tract irritation, bronchitis, bronchoconstriction Provocation of asthmatic episodes Exacerbation of cardiopulmonary diseases   Exercise, particles, asthma Nitrogen oxides (measured as nitrogen dioxide) (Biomass and fossil fuel combustion, tobacco smoke and exhaust fumes)   Eye irritation Respiratory tract infection (especially in children) Exacerbation of asthma, irritation of bronchi Asthma requiring hospital admission   Exercise, respiratory viruses, asthma Ozone (Secondary pollutant – traffic, hydrocarbon release, fossil fuel combustion)   Eye and respiratory tract irritation Reduced exercise capacity Exacerbation of asthma Asthma requiring hospital admission   Exercise, respiratory viruses, asthma

Some of the scientific evidence for these health effects includes:

A recent European study found that hospital admissions for asthma increase by 1 per cent for every 10 micrograms per cubic metre increase in particles with diameters less than 10 micrometres (known as PM10).^{1,<LE III-3>b}

• Associations between particles, ozone, nitrogen dioxide and asthma hospital admissions have been confirmed in Sydney, Brisbane and Melbourne.^{2,3,4,<LE III-3>}

• A recent study in Darwin demonstrated an association between modest levels of PM10 from bushfires and emergency attendances for asthma.^{5,<LE III-3>}

• Effects of particles on symptoms and lung function have not been confirmed in cohorts of children with asthma.^{6,<LE III-2>}

• However, other studies involving cohorts of children with asthma have shown clear effects of nitrogen oxides and ozone.⁷,<LE III-2> With more sensitive techniques health effects of ozone are observed at ever-lower concentrations.^{8,9,10,<LE II, III-1>}

• Prior exposure to ozone or nitrogen dioxide increases the response to allergens in people with allergic asthma.^{11,12,<LE II>}

• Long-term effects of air pollution appear to be related more to bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer,^{13,<LE III-2>} than to asthma.