Effects of bushfire smoke on daily mortality and hospital admissions in Sydney, Australia.
BACKGROUND
Little research has investigated the health effects of particulate exposure from bushfires (also called wildfires, biomass fires, or vegetation fires), and these exposures are likely to increase, for several reasons. We investigated associations of daily mortality and hospital admissions with bushfire-derived particulates, compared with particulates from urban sources in Sydney, Australia from 1994 through 2002.


METHODS
On days with the highest particulate matter (PM)10 concentrations, we assumed PM10 was due primarily to bushfires. We calculated the contribution of bushfire PM10 on these days by subtracting the background PM10 concentration estimated from surrounding days. We assumed PM10 on the remaining days was from usual urban sources. We implemented a Poisson model, with a bootstrap-based methodology, to select optimum smoothed covariate functions, and we estimated the effects of bushfire PM10 and urban PM10, lagged up to 3 days.


RESULTS
We identified 32 days with extreme PM10 concentrations due to bushfires or vegetation-reduction burns. Although bushfire PM10 was consistently associated with respiratory hospital admissions, we found no consistent associations with cardiovascular admissions or with mortality. A 10 microg/m increase in bushfire PM10 was associated with a 1.24% (95% confidence interval = 0.22% to 2.27%) increase in all respiratory disease admissions (at lag 0), a 3.80% (1.40% to 6.26%) increase in chronic obstructive pulmonary disease admissions (at lag 2), and a 5.02% (1.77% to 8.37%) increase in adult asthma admissions (at lag 0). Urban PM10 was associated with all-cause and cardiovascular mortality, as well as with cardiovascular and respiratory hospital admission, and these associations were not influenced by days with extreme PM10 concentrations.


CONCLUSIONS
PM10 from bushfires is associated primarily with respiratory morbidity, while PM10 from urban sources is associated with cardiorespiratory mortality and morbidity.
Morgan
Geoffrey
G
Northern Rivers University, Department of Rural Health, University of Sydney, Lismore, New South Wales, Australia. geoff.morgan@ncahs.health.nsw.gov.au
Sheppeard
Vicky
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Khalaj
Behnoosh
B
Ayyar
Aarthi
A
Lincoln
Doug
D
Jalaludin
Bin
B
Beard
John
J
Corbett
Stephen
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Lumley
Thomas
T
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005390:Fires / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009517:New South Wales / Q000453:epidemiology; D010316:Particle Size; D010343:Patient Admission / Q000639:trends*; D015208:Smoke Inhalation Injury / Q000401:mortality*; D055815:Young Adult