b'CARES Annual Report 2019 | 15CARES in ActionUsing CARES Data to Study Wildfire Smoke and Out-of-Hospital Cardiac Arrests in the 2015-2017 California Wildfires By Sumi Hoshiko, MPH, California Department of Public Health As the number and severity of wildfires has increased in recent years, so has scientific knowledge of the health impact of smoke from wildfires. While studies have shown increases in respiratory illnesses under smoky conditions produced by wildfires, a similar increase in cardiovascular illnesses has not been consistently seen. This has been puzzling, because decades of scientific research have linked ambient air pollution to cardiovascular problems. This prompted public health researchers in California to search for ways to investigate this question, and the CARES dataset on out-of-hospital-cardiac arrests provided just such an opportunity. We reasoned that because these cases often result in sudden death outside of a hospital, they may not have been captured in earlier wildfire studies of cardiovascular outcomes, as these studies typically use hospital-based datasets, explained senior author Sumi Hoshiko of the California Department of Public Health. It quickly became clear that CARES data could be invaluable in understanding the true relationship between wildfire smoke and a critical adverse cardiovascular event, and a collaborative research project was formed between CARES, the California Department of Public Health, and the United States Environmental Protection Agency.Fourteen counties in California with active CARES surveillance programs and that experienced wildfire smoke between 2015 to 2017 participated. During this time period, wildfires burned over 3 million acres across the state, exposing millions of people in different locations and points in time to wildfire smoke emissions. Satellite data from the National Oceanic and Atmospheric Association (NOAA) was used to categorize smoke plumes into none, light, medium and heavy density. By comparing exposure among cases on the day of their cardiac arrest with control days, investigators were able to study whether smoke was associated with increased numbers of cardiac arrests. The study also looked at whether those risks differed based on age, sex, and socioeconomic status. The latter was based on population income levels in the census tract where the cardiac event occurred.We saw that the number of cardiac arrests increased on days with heavy smoke exposure, but also that the risk seemed to persist for several days afterwards, explained Caitlin Jones, who led the analysis. While this was true for cases in both lower and higher socioeconomic categories on heavy smoke days, the lower socioeconomic group also appeared to be impacted on medium smoke days Map of the 14 California counties in the study region showing the(Figure on page 16).number of smoke days in each county from 20152017, based on NOAA HMS wildfire smoke plume.The finding that cases in lower socioeconomic areas were most affected is important to keep in mind when attempting to understand the effects of smoke exposure; in other words, there isnt a single, simple relationship between exposure and outcomeit varies depending on the vulnerability of the population exposed. There could be numerous explanations for this disparity; for example, underlying health problems may be more common and healthcare less accessible in low socioeconomic status communities. It could also be that persons in higher socioeconomic areas are better positioned to take protective action, such as leaving the area during smoky periods, staying indoors or using air filters in their home, and avoiding exertion, all of which could decrease smoke exposure and reduce the chances of a cardiac arrest during wildfires. Any single one of these factors, or a combination of these, might explain the disparity in risk based on socioeconomic status.'