Author: Thomas Grahame
Position: Senior Analyst
Institution: US Department of Energy
E-mail: thomas.grahame@hq.doe.gov
Submitted Date: September 09, 2008
Published Date: September 10, 2008
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

This isn't a full blown response, but rather a short augmentation to this very well done analysis. Below I briefly review some recent evidence suggesting that vehicular emissions are likely responsible for a significant share of lung cancers among non-smokers in the U.S. and Europe.

We have known for many years that vehicular emissions such as PAHs are capable of initiating lung cancer. Benzene and 1,3-butadiene are also likely carcinogens. But what does epidemiology tell us?

Recent research, with more precise subject exposure information than earlier epidemiology, tightens and better establishes lung cancer risks from exposure to such vehicular emissions. Garshick et al. (2008) examine lung cancer risks in trucking industry workers and find elevated lung cancer risks, not explained by smoking behavior, which for similarly exposed workers increase linearly with years of employment.

Jerrett et al. (2005), an analysis of the Los Angeles cohort of the American Cancer Society (ACS) cohort for this city, found that higher levels of intra-city PM2.5 were associated with increased lung cancer mortality risks. In Los Angeles, higher levels of PM2.5 are mostly due to higher vehicular emissions, given their ubiquity there, and the relative paucity of other emissions.

Nafstad et al. (2003, 2004) found risks of lung cancer mortality were significantly associated with higher levels of modeled vehicular emissions at residence. Nyberg et al. (2000) found a significant association for development of lung cancer with “traffic-related NO2 exposure 20 years” prior (RR = 1.4), and concluded that vehicular emissions are likely particularly important for lung cancer incidence. Vineis et al. (2004) found that lifetime cancer risks could be on the order of 1% to 2% for those occupationally exposed to diesel emissions, which is about two orders of magnitude higher than that for the general population. These latter four studies are all European.

These findings may explain much of the lung cancer incidence among non-smokers in the U.S. and Europe, since many people live adjacent to major roads in urbanized societies. Since lower income people and African Americans are more likely to live near such roads in the U.S., it seems reasonable that the higher lung cancer rates found in this study for African Americans might be due in part to greater exposure to vehicular emissions.

References

Garshick, E., et al. 2008. Lung Cancer and Vehicle Exhaust in Trucking Industry Workers. Environ. Health Perspect. 116 (in press, May 30 online)

Jerrett, M., Buzzelli, M., Burnett, R.T. and De Luca, P.F. 2005. Particulate air pollution, social confounders, and mortality in small areas of an industrial city. Social Science and Medicine 60:2845-2863.

Nafstad, P., Haheim, L. L., Oftedal, B., Gram, F., Holme, I., Hjermann, I., and Leren, P. 2003. Lung cancer and air pollution: A 27 year follow up of 16,209 Norwegian men. Thorax 58:1071–1076.

Nafstad, P., Haheim, L. L.,Wisloff, T., Gram, F., Oftedal, B., Holme, I., Hjermann, I., and Leren, P. 2004. Urban air pollution and mortality in a cohort of Norwegian men. Environ. Health Perspect. 112:610– 615.

Nyberg, F., Gustavsson, P., Jarup, L., Bellander, T., Berglind, N., Jakobsson, R., and Pershagen, G. 2000. Urban air pollution and lung cancer in Stockholm. Epidemiology 11:487–495.

Vineis, P., Forastiere, F., Hoek, G., and Lipsett, M. 2004. Outdoor air pollution and lung cancer: Recent epidemiologic evidence. Int. J. Cancer 111:647–652.