Atmosphere Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Dr Peter Manins, Environmental Consulting and Research Unit, CSIRO Atmospheric Research, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06746 9

Urban Air Quality (continued)

Indicators of the condition of air quality (continued)

PM2.5 in urban areas

  • Implications
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    Some studies from other countries have indicated that more deaths are attributable to the concentration of particulate matter of diameter below 2.5 m (PM2.5) than to the concentration of PM10. However, particles with sizes between 2.5 and 10 m may be more important in relation to asthma and respiratory illnesses (Denison 2000). There are few regular PM2.5 measurements undertaken in Australia, and no air quality standard has been set for PM2.5.

    Figure 105 gives the maximum PM2.5 values measured for Melbourne, Brisbane and Perth, whereas Figure 106 apportions the sources for the Perth readings during each of the seasons 1994 to 1995.

    Figure 105: Maximum 24 hour PM2.5 concentration for selected Australian cities.

     Maximum 24 hour PM2.5 concentration for selected Australian cities

    Source: State environmental authorities

    The PM2.5 to PM10 ratio varies with season (Table 20) and this is true in all Australian cities (Table 21). In every case the proportion of PM2.5 particles is higher in winter than in summer. Figure 106 shows typical sources of PM2.5-sized particles in Perth. The variation of PM2.5 in Perth since 1994 (Figure 107) indicates that the composition of the PM2.5 particles can change with season and with year. Much of the time it is smoke, from industrial or residential combustion, that is the dominant source but in certain years bushfires will add their contribution as well. During certain seasons other processes dominate. Occasionally this may be soil-based particles. Secondary production, which consists of chemical processes that convert gases into particles, can also produce a significant contribution.

    Table 20: Analysis of 24-hour PM10 and 24-hour PM2.5 data for Melbourne from 1988 to 1996
      Whole study period Cool season (April-Oct.) Warm season (Nov.-Mar.)
      Mean s.d. Min. Max. Mean s.d. Min. Max. Mean s.d. Min. Max.
    PM10 18.97 6.99 11.31 79.59 18.53 7.43 11.31 79.59 19.6 .24 12.55 76.81
    PM2.5 9.42 3.65 6.15 42.58 9.85 4.00 6.18 42.58 8.79 2.97 6.15 35.33

    Source: EPAV (2000b: Table B4a).

    Table 21: Ratio of PM2.5 to PM10 based on episodic measurements
    City Winter ratio Summer ratio
    Brisbane 0.44 0.26
    MelbourneA 0.53 0.44
    Melbourne 0.60 0.40
    Sydney 0.58-0.80 0.41

    A See Table 20.

    Source: NEPC (1998).

    Figure 106: Source contributions to PM2.5 concentrations in the Perth Metropolitan Region between winter 1994 and winter 1995 recorded during the Perth Haze Study.

     Source contributions to PM2.5 concentrations in the Perth Metropolitan Region between winter 1994 and winter 1995 recorded during the Perth Haze Study

    Source: DEP (2000)

    Figure 107: Annual maximum, 90th and 50th percentiles (median) and 10th percentile of maximum 24 hour PM2.5 concentrations from Perth (Caversham).

     Annual maximum, 90th and 50th percentiles (median) and 10th percentile of maximum 24 hour PM2.5 concentrations from Perth (Caversham)

    Source: Data from Department of Environmental Protection, WA

    Implications

    Australia does not have a PM2.5 standard, although the issue is being considered by NEPC. On the basis of the above results, the NEPM 24-hour PM10 standard of 50 g/m3 limits the atmospheric PM2.5 concentrations to between 20 and 40 g/m3 depending on the city and the season. This means that the NEPM provides an upper limit to the PM2.5 concentration that is more stringent than the United States EPA 24-hour PM2.5 standard of 65 g/m3 set in 1997. The United States also set an annual PM2.5 concentration of 15 g/m3. This indicates that long-term standards for particulate matter are needed.