Air pollution, viral spread and health outcomes evidence from strikes in France
利用法国十大城市2010-2015年公交罢工作为自然实验，发现公交停运导致私家车增加，既因空气污染加重而增加呼吸系统住院，又因人际接触减少而降低病毒传播，两种效应相互抵消。
To evidence the impact of air pollution on the health of urban populations, several studies use natural experiments that shift commuting from public transport to cars (or vice-versa). However, as public transport use declines, reduced interpersonal contact may lead to slower virus spread and thus lower respiratory morbidity. Using a difference-in-differences strategy, we show that respiratory hospitalisations are both positively affected by air pollution and negatively affected by viral spread following partial unavailability of public transport due to strikes in the ten most populated French cities during the period 2010-2015. Our results are in line with studies in other countries that have found a significant increase in urgent respiratory hospitalisations following a public transport strike, most likely due to car pollution, but we also find a detectable interaction with viral spread, which should not be overlooked when interpreting these studies.