Biomass burning and respiratory illness in the tropical savannas of Australia

Background: Darwin is uniquely placed to study particulates arising from biomass burning because of (i) a dry season climate with little variation in meteorological conditions over the austral winter months; (ii) predictable high frequency of landscape fires (\u27bushfires\u27) of variable intensity and extent with corresponding fluctuations in air quality; (iii) the absence of heavy industry and (iv) a single medical data registry. During the dry season approximately 96% of all atmospheric pollution consists of carbon particulates arising from bushfire smoke. As part of implementation of national environment protection measure for air quality the NT government commissioned a study to examine potential health impacts of the haze. Methods: An ecological study conducted over the seven-month dry season. We examined the relationship between the mean atmospheric concentration of particles of 10 microns or less in aerodynamic diameter (PM10), per cubic meter, per 24-hour period and the daily number of presentations for asthma to the Emergency Department of Royal Darwin Hospital. Weekly general practice consultation rate for influenza-like illness, day of week, and school holiday periods were included as a potential confounders. Negative binomial regression was used to compare exposure and outcome measures. Results: There was a significant increase in asthma presentations with 10ugm-3 increases in PM10 the adjusted incidence rate ratio (IRR) being 1.26 95% CI 1.12-1.41, p < 0.001. The greatest association occurred on days in which the PM10 was above 40 ugm-3 (adjusted IRR 2.47 (95% CI 1.21-5.01), compared with days when PM10 levels were less than 10 ugm-3. Conclusions: This study found a strong association between asthma and low, relative to current air quality standards, concentrations of atmospheric particulates. However it was of small scale, did not adjust for mould and pollen counts, meteorological conditions or autocorrelation of data. A more comprehensive research program is required addressing these epidemiological issues as well as ecological and meteorological factors that result in production of high concentrations of particulates such as fuel types and atmospheric inversions. While reduction of smoke pollution, at the very least to below the current national air pollution guidelines, will improve human health outcomes, achieving this public health goal demands a trans-disciplinary approach including landscape ecology, meteorology, atmospheric chemistry and epidemiology