Living in a land of fire
Professor Rob Whelan, University of Wollongong
Professor Peter Kanowski, Australian National University
Dr Malcolm Gill, Australian National University
Dr Alan Andersen, CSIRO Tropical Ecosystems Research Centre
prepared for the 2006 Australian State of the Environment Committee, 2006
Emissions from bushfires can affect human health through increasing the levels of smoke particles, carbon monoxide, air toxics and volatile organic carbons in the air, and they can raise the concentration of ground-level ozone. The nationally-agreed standards for air quality, the National Environment Protection (Ambient Air Quality) Measures, specify threshold levels for pollutant emissions; for example, for particles of 10 microns or less in diameter (PM10) is a maximum mean atmospheric concentration of 50 µg/mm³ over a 24-hour period.
Major bushfire events typically generate particulate concentrations well beyond the threshold National Environment Protection Measures level. For example, in the 1994 Sydney bushfires, the peak was 210 µg/mm³ (compared with a background level from non-bushfire sources of 30 µg/mm³); during Sydney’s Christmas 2001 bushfires, levels above 150 µg/mm³ were sustained for ten days; in Canberra on 18 January 2003, the maximum level was 192 µg/mm³. Fuel reduction burning can also prejudice air quality, especially because the weather conditions under which it is carried out can mean that emissions are retained in urban air sheds for extended periods.
Although studies in the 1990s failed to find statistically significant correlations between bushfire smoke and asthma, a study in Darwin from April to October 2000 did reveal a relationship. Darwin experiences bushfires throughout the dry season: planned fuel reduction burning occurs mostly from April to June, and unplanned bushfires occur mostly late in the dry season. The study examined the concentration of respirable particles arising from all bushfires (both planned and unplanned) with attendance at hospital. The PM10 levels ranged from only two to 70 µg/mm³, with peak fire activity in September, when the National Environment Protection Measures standard was exceeded on five days. There was a significant increase in asthma presentations to hospital with each 10 µg/mm³ increase in PM10, especially when the PM10 level exceeded 40 µg/mm³. The study concluded that airborne particulates from bushfires should be regarded as just as injurious to human health as airborne particulates from other sources.
The challenge to land and bushfire managers is to manage fuel loads without exceeding threshold air quality standards. An example of how this challenge is being approached is that from south-west Western Australia, where a regular program of fuel reduction is undertaken, mainly in spring. In response to concerns about impacts on air quality in Perth and other urban centres, the Western Australian Government has developed an Air Quality Management Plan. The public land manager, the Department of Conservation and Land Management, is required to plan its fuel reduction activities to minimise urban air quality impacts. It has been largely successful in doing so, with national standard thresholds now exceeded only rarely.
Land and bushfire managers in other Australian states and territories are responding similarly to minimise the adverse impacts of emissions from bushfires on air quality and human health. These mitigation strategies are being informed by research coordinated by the Bushfire Cooperative Research Centre.