Abstract:
Public warning systems reduce one health risk while potentially creating another. Using daily metropolitan city-level data from South Korea (2015–2019) and the rollout of real-time Emergency Alerts, I show that particulate matter warnings increase influenza incidence only when delivered through high-salience mobile channels. The effect emerges after Emergency Alert implementation, peaks 25–40 days after warnings, and is concentrated among school-aged children. Evidence from online search behavior suggests warning-induced indoor congregation as the mechanism. Falsification tests show no effects on unrelated conditions, indicating a behavioral transmission channel rather than pollution exposure alone.

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

JEL Codes: D83, Q53, I18, I12

Figure 1. Event Study: Dynamic Effects of PM Warnings Before and After the Emergency Alerts