Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM2.5)]. This is the first national-level cohort study to investigate these risks in Canada. The authors investigated the association between long-term exposure to ambient PM2.5 and cardiovascular mortality in nonimmigrant Canadian adults.

Only about 30% of breast cancer cases can be explained by accepted risk factors. Crouse et al. (p. 1578) investigated whether the incidence of postmenopausal breast cancer may be associated with exposure to urban air pollution. The authors used data from a hospital-based case