Air pollution: size counts

A study of atmospheric particles in Australian cities has provided new information on tiny particles that are believed to be most dangerous to human health.

The research, carried out by Dr Melita Keywood from CSIRO, has identified for the first time in Australia the chemical make-up of different sized particles in the air. Tiny particles, which can penetrate deep into the lungs, contain toxic and cancer-causing chemicals. The chemicals include lead, black carbon and complex organic compounds.

The research compared atmospheric particles in Australian cities using the same measurement technique at all sites. In the past, comparisons of particle levels in air have been difficult as State and Territory agencies use different instruments and different techniques for measuring pollution.

Particles in the air come from motor vehicles emissions, domestic wood burning, industry and natural sources, and often contribute to haze as well as health problems.  Particles range in size from large (greater than 10 micrometres) to very small (less than 0.01 micrometre).

Dr Keywood and colleagues measured levels of particles smaller than 10 micrometres in diameter in Sydney, Melbourne, Adelaide, Brisbane, Canberra and Launceston during seasons in which air pollution was expected to be most severe.

Sydney, Brisbane, Melbourne and Adelaide had average particle concentrations of between 20 and 25 micrograms per cubic metre.  Despite the cities’ smaller sizes, average concentrations in Canberra and Launceston were two- to three-times greater than in the other four cities, with smaller particles making up a larger proportion of the particle concentration in Launceston and Canberra.

‘At times, particle levels in Canberra and Launceston are amongst the highest in Australia,’ says Dr Keywood.

‘Domestic wood fires in winter, combined with light winds and the locations of the two cities in valleys, cause high pollution readings,’ says Dr Keywood.

The Australian air quality standard for particles is based on concentration of all particles smaller than 10 micrometres.  However, the particles that harm us most are believed to be those well below 10 micrometres in size.  This research has shown that these smaller particles do contain some of the toxic and carcinogenic chemicals of concern to human health.

Tiny particles are more likely than larger particles to be responsible for adverse health impacts with elderly and children most at risk, along with people having existing respiratory illnesses.

The results of this work and those from other studies provide important input to the ongoing development of air quality standards, thus potentially reducing the health risk associated with exposure to air pollution.

Dr Keywood’s research was sponsored by Environment Australia and performed by CSIRO in collaboration with ANSTO.

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