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Vegetation fire smoke, indigenous status and cardio respiratory hospital admissions in Darwin, Australia, 1996-2005


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Hanigan, IC, Johnston, FH and Morgan, GG 2008 , 'Vegetation fire smoke, indigenous status and cardio respiratory hospital admissions in Darwin, Australia, 1996-2005' , Environmental Health, vol. 7, no. 5 Augu , p. 3 , doi: 10.1186/1476-069X-7-42.

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Background: Air pollution in Darwin, Northern Australia, is dominated by smoke from seasonal fires in the
surrounding savanna that burn during the dry season from April to November. Our aim was to study the
association between particulate matter less than or equal to 10 microns diameter (PM10) and daily emergency
hospital admissions for cardio-respiratory diseases for each fire season from 1996 to 2005. We also investigated
whether the relationship differed in indigenous Australians; a disadvantaged population sub-group.
Methods: Daily PM10 exposure levels were estimated for the population of the city from visibility data using a
previously validated model. We used over-dispersed Poisson generalized linear models with parametric
smoothing functions for time and meteorology to examine the association between admissions and PM10 up to
three days prior. An interaction between indigenous status and PM10 was included to examine differences in the
impact on indigenous people.
Results: We found both positive and negative associations and our estimates had wide confidence intervals.
There were generally positive associations between respiratory disease and PM10 but not with cardiovascular
disease. An increase of 10 μg/m3 in same-day estimated ambient PM10 was associated with a 4.81% (95%CI: -1.04%,
11.01%) increase in total respiratory admissions. When the interaction between indigenous status and PM10 was
assessed a statistically different association was found between PM10 and admissions three days later for
respiratory infections of indigenous people (15.02%; 95%CI: 3.73%, 27.54%) than for non-indigenous people
(0.67%; 95%CI: -7.55%, 9.61%). There were generally negative estimates for cardiovascular conditions. For nonindigenous
admissions the estimated association with total cardiovascular admissions for same day ambient PM10
and admissions was -3.43% (95%CI: -9.00%, 2.49%) and the estimate for indigenous admissions was -3.78%
(95%CI: -13.4%, 6.91%), although ambient PM10 did have positive (non-significant) associations with cardiovascular
admissions of indigenous people two and three days later.
Conclusion: We observed positive associations between vegetation fire smoke and daily hospital admissions for
respiratory diseases that were stronger in indigenous people. While this study was limited by the use of estimated
rather than measured exposure data, the results are consistent with the currently small evidence base concerning
this source of air pollution.

Item Type: Article
Authors/Creators:Hanigan, IC and Johnston, FH and Morgan, GG
Journal or Publication Title: Environmental Health
ISSN: 1832-3367
DOI / ID Number: 10.1186/1476-069X-7-42
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