There was no information on residential mobility after enrollment; however, never-smoking participants reported living in their current neighborhood at enrollment for a mean number (SD) of 20.7 (14.9) years.
Misclassification because of residential mobility would also likely be nondifferential, biasing estimated RR estimates toward unity.
No updated data on cigarette smoking or other individual-level covariates of interest were collected from enrollment in the full CPS-II; however, it is unlikely that lifelong never-smokers in the cohort with an average age at enrollment of 57 years would begin smoking during follow-up.
There may also have been changes in other sociodemographic ecologic-level factors over time; however, little change in results was observed on the inclusion of sociodemographic ecologic covariates in the model from any three of the time periods considered (1980s, 1990s, or 2000s).
Although the present study was based on mortality, inferences about the incidence of highly fatal diseases, such as lung cancer, may be reasonably approximated using mortality-based data.
Similar associations between ambient air pollution and lung cancer incidence and mortality were also observed in other recent work (23, 24, 28, 29).
There was no information available on the histologic subtype of lung cancer. Results from a Danish study reported stronger associations between estimated NOx concentrations and incident small-cell carcinoma and squamous cell carcinoma than adenocarcinoma (30).