Abstract:
Air pollution warnings aim to protect public health by reducing outdoor exposure, yet they can generate unintended consequences. Using daily province-level panel data from South Korea (2015–2019), this study shows that particulate matter warnings increase influenza incidence by roughly 10–15 percent, with the largest effects among children and teenagers. The impact emerges gradually and peaks 25–40 days after a warning, consistent with secondary transmission dynamics. Search data indicate a shift toward indoor activities and pollution-related items, supporting a behavioral response that increases indoor congregation. Effects are stronger after the 2017 rollout of Emergency Disaster Texts, on business days, and in densely populated, lower-income regions. The increase is concentrated in outpatient cases, suggesting mainly mild to moderate illness. Robustness checks and welfare calculations show that excess flu cases impose substantial additional healthcare costs. Overall, while PM warnings reduce pollution exposure, they may inadvertently raise viral transmission risk by driving people indoors.


Keywords: Air pollution; Behavioral response; Information policy; Influenza; Alert