Lung adenocarcinoma incidence rates and their relation to motor vehicle density

The temporal trend of adenocarcinoma incidence rates of the lung (ADL) has been reported to parallel the trend of nitrogen oxide (NOx) emissions in the United States. This study explores the geographic pattern of ADL incidence and its relation to motor vehicle density, the major indicator of NOx emissions before 1970.

ADL incidence rates by counties were retrieved from the nine sites of Surveillance, Epidemiology, and End Results (SEER) Program for the period of 1973 to 1990. Motor vehicle densities by county in 1970 for these SEER sites were estimated according to the numbers of motor vehicle registration and the size of each county. Regression analysis was done with the data of motor vehicle density by counties.

A dose-response pattern between motor vehicle density and ADL incidence was found. The risks are 136% and 68% higher for ADL and squamous cell carcinoma, respectively, for male residents living in areas with 937 motor vehicles per square mile, compared with those living in areas with about one motor vehicle per square mile. The R2 are as high as 0.805 and 0.504 in regressions for male incidence rates of ADL and squamous cell carcinoma, respectively, with the vehicle density values. As a comparison, the prostate cancer incidence rates did not show dose-response relationship with motor vehicle density. If the effect of NOx emissions on ADL incidence rates can be proved by further studies, the current standard of allowance of NOx emissions may need to be revised.