Short-term health effects of public transport disruptions: air pollution and viral spread channels

When public transport supply decreases, urban population health may be strongly affected. First, as ambient air pollution increases, respiratory diseases may be exacerbated during a few days. Second, reduced interpersonal contacts may lead to a slower viral spread, and therefore, after a few incubation days, lower morbidity. We evidence these two channels, using a difference-in-differences strategy, considering public transport strikes in the ten most populated French cities over the 2010-2015 period. On the two days following the strike, we find less emergency hospital admissions for influenza and gastroenteritis. In spite of the existence of this contagion channel, which tends to mitigate the increase of admissions for respiratory diseases, we also evidence a substantial air pollution channel. On the strike day, we find more admissions for acute diseases of the upper respiratory system, while on the following day of the strike, more abnormalities of breathing. Our results suggest that urban population daily transportation choices do matter as they engender dynamic spillovers on health.