Abstract:
Air-quality warnings aim to protect public health by reducing outdoor exposure but may generate unintended behavioral spillovers. Using daily province-level data from South Korea (2015–2019) and exploiting the staggered rollout of real-time Emergency Disaster Texts (EDT), I show that particulate matter (PM) warnings increase influenza incidence through an information-driven behavioral response. A difference-in-differences analysis finds that post-warning flu incidence rises significantly after EDT implementation, an effect absent in the pre-EDT period. Event-study estimates reveal no pre-trend, with incidence beginning to rise around day 3 and peaking 25–40 days after an alert — consistent with secondary transmission chains seeded by warning-induced indoor congregation rather than a single incubation cycle. High-frequency search data confirm that warnings trigger rapid substitution toward commercial indoor venues, with behavioral reversion within two days, supporting the interpretation that a brief congregation episode generates a prolonged epidemiological arc. Effects are concentrated among school-aged children and stronger in areas with greater alert exposure. Falsification tests show that physical pollution shocks predict external-organ conditions such as dermatitis, while only the warning signal predicts influenza, isolating an informational behavioral channel from direct biological exposure. These findings highlight nontrivial hidden externalities in environmental alert design and suggest that coupling pollution warnings with indoor hygiene guidance could mitigate the unintended epidemiological costs of high-salience alert systems.


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