In 2023 there was a similar Canadian wildfire smoke pollution issue in the United States as there was in July 2026. The CDC found:
“Emergency department visits for asthma were 17% higher than expected during 19 days of wildfire smoke that occurred during April–August 2023.”
References
McArdle CE, Dowling TC, Carey K, et al. Asthma-Associated Emergency Department Visits During the Canadian Wildfire Smoke Episodes — United States, April– August 2023. MMWR Morb Mortal Wkly Rep 2023;72:926–932. DOI: http://dx.doi.org/10.15585/mmwr.mm7234a5.