Wildfire smoke and risk of out-of-hospital cardiac arrests using a spatially derived exposure metric for 2015-2017 California wildfires
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1
Environmental Health Investigations Branch, California Department of Public Health, United States
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2
United States Environmental Protection Agency, United States
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3
Office of Health Equity, California Department of Public Health, United States
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4
Emory University, United States
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5
Environmental Health Investigations Branch, California Department of Public Health, United States
Background – Changes in climate are disrupting natural cycles of wildfires. The increasing burden of wildfire smoke in California continues to create adverse health effects in exposed populations, yet the cardiovascular health impacts are not well understood. Out-of-hospital cardiac arrests (OHCA) contribute substantially to premature deaths and 70% do not survive to hospital admission. Using this novel endpoint allows examination of a critical outcome not fully captured in typical wildfire smoke studies, which generally use hospital admission and emergency department datasets.
Methods – We examined the relationship of wildfire smoke exposures and cardiac arrest occurring outside a hospital setting using categorical estimates of wildfire-related PM2.5 (light, medium, heavy smoke) derived from satellite-imagery on the National Oceanic Atmospheric Association’s Hazard Mapping System Smoke Product. Surveillance data of EMS-attended out-of-hospital cardiac arrests (OHCA) in adults (>18 years of age) was provided by the Cardiac Arrest Registry to Enhance Survival for 14 California counties during wildfire months, May – October, 2015-2017 (N=5,336). Geocoded locations of OHCA event occurrences were spatially linked with daily maximum wildfire smoke at the census tract level, aggregated from values at block group centroids, for lag days 0-3, where lag day 0 is OHCA event on same day as exposure, lag day 1 is OHCA event 1 day following exposure, and so on. We applied conditional logistic regression incorporating a spline for heat index in a case crossover design (matching smoke exposures with OHCA cases and 4 referent day controls from 1, 2, 3, and 4 weeks prior to case date). We stratified models by sex, age (19-34, 35-64 and ≥ 65), and socioeconomic status (SES; census tract percent living below poverty).
Results – OHCA risk increased at heavy smoke densities (>22 µg/m3) across multiple lag days, strongest on lag day 2 (OR 1.70, 95% CI 1.18 - 2.13). Lower SES cases tended to experience more pronounced impacts across all exposure categories. Higher SES cases had elevated odds ratios with heavy smoke (OR 1.60; 95% CI 1.07 - 2.40), but null results with light and medium smoke. Both sexes and age groups 35 and above were impacted at heavy smoke densities.
Conclusions – This study presents novel findings on the relationship of OHCA and wildfire smoke in the United States, providing supporting evidence for an effect of wildfire smoke on cardiovascular mortality and morbidity. Consistent with many environmental exposures, the lower SES population appeared to be more vulnerable to the effects of wildfire smoke. Further investigation can help explain the differential effects by SES and sex by examining differences in biologic susceptibility, exposure vulnerability, and adaptive capacity. Results from this study can also inform interventions most relevant to vulnerable populations during wildfire events.
Note: This does not necessarily reflect US EPA policy.
Keywords:
Out-of-Hospital Cardiac Arrest,
Wildfire smoke,
Cardiovascular health,
Particulate matte,
Air Quality Index
Conference:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data, Davis, United States, 8 Oct - 10 Oct, 2019.
Presentation Type:
Regular oral presentation
Topic:
Spatial methods for environmental & exposure epidemiology and climate change
Citation:
Jones
CG,
Rappold
AG,
Vargo
J,
Cascio
WE,
Surveillance Group
C and
Hoshiko
S
(2019). Wildfire smoke and risk of out-of-hospital cardiac arrests using a spatially derived exposure metric for 2015-2017 California wildfires.
Front. Vet. Sci.
Conference Abstract:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data.
doi: 10.3389/conf.fvets.2019.05.00038
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Received:
21 Jun 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Ms. Caitlin G Jones, Environmental Health Investigations Branch, California Department of Public Health, Richmond, California, United States, Caitlin.Jones@cdph.ca.gov