Abstract:
Air pollution warnings aim to protect public health by reducing outdoor pollution exposure; however, such alerts can generate unintended consequences. Using daily province-level panel data from South Korea (2015–2019), this study finds that particulate matter (PM) warnings significantly increase influenza incidence by approximately 10–15 percent on average, with the strongest effects among children and teenagers. The impact emerges gradually, peaking 25–40 days after a warning, consistent with secondary transmission dynamics. Effects are amplified following the 2017 introduction of mobile Emergency Disaster Texts (EDTs), on business days, and in densely populated, lower-income regions prone to indoor crowding. Supplemental analysis shows the increase is confined to outpatient cases, indicating mainly mild to moderate illness. Extensive robustness analyses and back-of-the-envelope welfare calculations reveal that excess flu cases attributable to warnings impose substantial additional healthcare costs, highlighting a behavioral spillover of environmental policy. These findings underscore a critical trade-off: while PM warnings reduce pollution exposure, they may inadvertently elevate viral transmission risk through increased indoor congregation.


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