It is often said that it is better to exercise than remain sedentary, even in heavily polluted environments. These statements are based on modelling studies that draw their data from empirical investigations of the dose response curves for increasing activity and increasing pollution (as measured by particulates in the range 5-200 mg/m3):
A recent modelling study  finds that the balance of harms to benefits does not become adverse except in the cities at the very highest end of the distribution of pollution levels, i.e. levels seldom seen, even in heavily polluted cities. However, these studies do not consider the other risks of certain activities, such as cycling, which, we think, should be included in such models.
— Richard Lilford, CLAHRC WM Director
- Tainio M, de Nazelle AJ, Götschi T, et al. Can air pollution negate the health benefits of cycling and walking? Prevent Med. 2016; 87:233-6.