Asthma-Associated Emergency Department Visits During the Canadian Wildfire Smoke Episodes - United States, April- August 2023

Abstract

During April 30-August 4, 2023, smoke originating from wildfires in Canada affected most of the contiguous United States. CDC used National Syndromic Surveillance Program data to assess numbers and percentages of asthma-associated emergency department (ED) visits on days with wildfire smoke, compared with days without wildfire smoke. Wildfire smoke days were defined as days when concentrations of particulate matter (particles generally ≤2.5 μm in aerodynamic diameter) (PM_2.5) triggered an Air Quality Index ≥101, corresponding to the air quality categorization, "Unhealthy for Sensitive Groups." Changes in asthma-associated ED visits were assessed across U.S. Department of Health and Human Services regions and by age. Overall, asthma-associated ED visits were 17% higher than expected during the 19 days with wildfire smoke that occurred during the study period; larger increases were observed in regions that experienced higher numbers of continuous wildfire smoke days and among persons aged 5-17 and 18-64 years. These results can help guide emergency response planning and public health communication strategies, especially in U.S. regions where wildfire smoke exposure was previously uncommon.

FIGURE 1

Trends in asthma-associated emergency department visits (A), excess asthma-associated emergency department visit detection (B), and the percentage of air quality monitors* reporting concentrations of fine particulate matter ≤2.5 μm in aerodynamic diameter indicative of wildfire smoke (C), by day — U.S. Department of Health and Human Services Region 2,^† April 30, 2023–August 4, 2023^§ Abbreviation: PM_2.5 = particulate matter with aerodynamic diameter ≤2.5 μm. * https://www.airnow.gov/aqi/aqi-basics/ ^† New Jersey and New York (Puerto Rico and U.S. Virgin Islands do not report data to the National Syndromic Surveillance Program). ^§ A wildfire smoke exposure day occurs when at least one air quality monitor in the region reports PM_2.5 concentrations corresponding to an Air Quality Index of ≥101.

FIGURE 2

Trends in asthma-associated emergency department visits (A), excess asthma-associated emergency department visit detection (B), and the percentage of air quality monitors* reporting concentrations of fine particulate matter ≤2.5 μm in aerodynamic diameter indicative of wildfire smoke (C), by day — U.S. Department of Health and Human Services Region 3,^† April 30, 2023–August 4, 2023^§ Abbreviation: PM_2.5 = particulate matter with aerodynamic diameter ≤2.5 μm. * https://www.airnow.gov/aqi/aqi-basics/ ^† Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia. ^§ A wildfire smoke exposure day occurs when at least one air quality monitor in the region reports PM_2.5 concentrations corresponding to an Air Quality Index of ≥101.

FIGURE 3

Trends in asthma-associated emergency department visits (A), excess asthma-associated emergency department visit detection (B), and the percentage of air quality monitors* reporting concentrations of fine particulate matter ≤2.5 μm in aerodynamic diameter indicative of wildfire smoke (C), by day — U.S. Department of Health and Human Services Region 5,^† April 30, 2023–August 4, 2023^§ Abbreviation: PM_2.5 = particulate matter with aerodynamic diameter ≤2.5 μm. * https://www.airnow.gov/aqi/aqi-basics/ ^† Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. ^§ A wildfire smoke exposure day occurs when at least one air quality monitor in the region reports PM_2.5 concentrations corresponding to an Air Quality Index of ≥101.