Severe episodic air pollution blankets entire cities and regions and have a profound impact on humans and their activities. We compiled daily fine particle (PM_2.5) data from 100 cities in five continents, investigated the trends of number, frequency, and duration of pollution episodes, and compared these with the baseline trend in air pollution. We showed that the factors contributing to these events are complex; however, long-term measures to abate emissions from all anthropogenic sources at all times is also the most efficient way to reduce the occurrence of severe air pollution events. In the short term, accurate forecasting systems of such events based on the meteorological conditions favouring their occurrence, together with effective emergency mitigation of anthropogenic sources, may lessen their magnitude and/or duration. However, there is no clear way of preventing events caused by natural sources affected by climate change, such as wildfires and desert dust outbreaks.

严重的偶发性空气污染覆盖了整个城市和地区，对人类及其活动产生了深远的影响。我们编制了每日细颗粒物（PM _2.5) 来自五大洲 100 个城市的数据，调查了污染事件的数量、频率和持续时间的趋势，并将其与空气污染的基线趋势进行了比较。我们表明，促成这些事件的因素是复杂的；但是，始终采取长期措施减少所有人为来源的排放，也是减少严重空气污染事件发生的最有效方法。在短期内，基于有利于此类事件发生的气象条件的准确预报系统，以及对人为源的有效紧急缓解，可能会降低其规模和/或持续时间。然而，没有明确的方法来预防受气候变化影响的自然资源引起的事件，例如野火和沙漠沙尘暴。