The relationship between air pollution and premature mortality is most often studied using time-series analysis of daily observations of the number of deaths and pollution levels. These studies capture the effects of short-term exposure to pollution on the probability of dying. The underlying assumption is that there is a distribution of susceptibility to the effects of air pollution in any population. People who are in a weakened physical state or who have a history of chronic obstructive pulmonary disease (COPD) or cardio-pulmonary problems are thought to be the most vulnerable. In the case of a sharp rise in pollution, the most vulnerable.
