The relationship of respiratory and cardiovascular hospital admissions to the southern California wildfires of 2003
- R J Delfino1,
- S Brummel2,
- J Wu1,3,
- H Stern2,
- B Ostro4,
- M Lipsett5,
- A Winer6,
- D H Street7,
- L Zhang5,
- T Tjoa1,
- D L Gillen2
- 1Department of Epidemiology, School of Medicine, University of California, Irvine, California, USA
- 2Department of Statistics, School of Information and Computer Science, University of California, Irvine, California, USA
- 3Program in Public Health, University of California, Irvine, California, USA
- 4Air Pollution Epidemiology Section, California Office of Environmental Health Hazard Assessment, Oakland, California, USA
- 5Exposure Assessment Section, Environmental Health Investigations Branch, California Department of Health Services, Oakland, California, USA
- 6Department of Environmental Health Sciences, School of Public Health, University of California, Los Angeles, California, USA
- 7Independent consultant, Salem, Oregon, USA
- Dr Ralph J Delfino, Epidemiology Department, School of Medicine, University of California, Irvine, 100 Theory Dr., Suite 100, Irvine, CA 92617-7555, USA;
- Accepted 18 August 2008
- Published Online First 18 November 2008
Objective: There is limited information on the public health impact of wildfires. The relationship of cardiorespiratory hospital admissions (n = 40 856) to wildfire-related particulate matter (PM2.5) during catastrophic wildfires in southern California in October 2003 was evaluated.
Methods: Zip code level PM2.5 concentrations were estimated using spatial interpolations from measured PM2.5, light extinction, meteorological conditions, and smoke information from MODIS satellite images at 250 m resolution. Generalised estimating equations for Poisson data were used to assess the relationship between daily admissions and PM2.5, adjusted for weather, fungal spores (associated with asthma), weekend, zip code-level population and sociodemographics.
Results: Associations of 2-day average PM2.5 with respiratory admissions were stronger during than before or after the fires. Average increases of 70 μg/m3 PM2.5 during heavy smoke conditions compared with PM2.5 in the pre-wildfire period were associated with 34% increases in asthma admissions. The strongest wildfire-related PM2.5 associations were for people ages 65–99 years (10.1% increase per 10 μg/m3 PM2.5, 95% CI 3.0% to 17.8%) and ages 0–4 years (8.3%, 95% CI 2.2% to 14.9%) followed by ages 20–64 years (4.1%, 95% CI −0.5% to 9.0%). There were no PM2.5–asthma associations in children ages 5–18 years, although their admission rates significantly increased after the fires. Per 10 μg/m3 wildfire-related PM2.5, acute bronchitis admissions across all ages increased by 9.6% (95% CI 1.8% to 17.9%), chronic obstructive pulmonary disease admissions for ages 20–64 years by 6.9% (95% CI 0.9% to 13.1%), and pneumonia admissions for ages 5–18 years by 6.4% (95% CI −1.0% to 14.2%). Acute bronchitis and pneumonia admissions also increased after the fires. There was limited evidence of a small impact of wildfire-related PM2.5 on cardiovascular admissions.
Conclusions: Wildfire-related PM2.5 led to increased respiratory hospital admissions, especially asthma, suggesting that better preventive measures are required to reduce morbidity among vulnerable populations.
▸ Additional information is published online only at http://oem.bmj.com/content/vol66/issue3
Funding: This study was funded by the South Coast Air Quality Management District contract no. 04182, and the National Institutes of Health, National Institute of Environmental Health Sciences grant no. ES-11615.
Competing interests: None.