Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Meta-Analysis
. 2015 Nov;123(11):1107-12.
doi: 10.1289/ehp.1408882. Epub 2015 Apr 14.

Lung Cancer and Exposure to Nitrogen Dioxide and Traffic: A Systematic Review and Meta-Analysis

Ghassan B Hamra  1 , Francine Laden, Aaron J Cohen, Ole Raaschou-Nielsen, Michael Brauer, Dana Loomis
Affiliations
Meta-Analysis

Lung Cancer and Exposure to Nitrogen Dioxide and Traffic: A Systematic Review and Meta-Analysis

Ghassan B Hamra et al. Environ Health Perspect. 2015 Nov.

Abstract

Background and objective: Exposure to traffic-related air pollutants is an important public health issue. Here, we present a systematic review and meta-analysis of research examining the relationship of measures of nitrogen oxides (NOx) and of various measures of traffic-related air pollution exposure with lung cancer.

Methods: We conducted random-effects meta-analyses of studies examining exposure to nitrogen dioxide (NO2) and NOx and its association with lung cancer. We identified 20 studies that met inclusion criteria and provided information necessary to estimate the change in lung cancer per 10-μg/m3 increase in exposure to measured NO2. Further, we qualitatively assessed the evidence of association between distance to roadways and traffic volume associated with lung cancer.

Results: The meta-estimate for the change in lung cancer associated with a 10-μg/m3 increase in exposure to NO2 was 4% (95% CI: 1%, 8%). The meta-estimate for change in lung cancer associated with a 10-μg/m3 increase in NOx was similar and slightly more precise, 3% (95% CI: 1%, 5%). The NO2 meta-estimate was robust to different confounding adjustment sets as well as the exposure assessment techniques used. Trim-and-fill analyses suggest that if publication bias exists, the overall meta-estimate is biased away from the null. Forest plots for measures of traffic volume and distance to roadways largely suggest a modest increase in lung cancer risk.

Conclusion: We found consistent evidence of a relationship between NO2, as a proxy for traffic-sourced air pollution exposure, with lung cancer. Studies of lung cancer related to residential proximity to roadways and NOx also suggest increased risk, which may be attributable partly to air pollution exposure. The International Agency for Research on Cancer recently classified outdoor air pollution and particulate matter as carcinogenic (Group 1). These meta-analyses support this conclusion, drawing particular attention to traffic-sourced air pollution.

Citation: Hamra GB, Laden F, Cohen AJ, Raaschou-Nielsen O, Brauer M, Loomis D. 2015. Lung cancer and exposure to nitrogen dioxide and traffic: a systematic review and meta-analysis. Environ Health Perspect 123:1107-1112; http://dx.doi.org/10.1289/ehp.1408882.

PubMed Disclaimer

Conflict of interest statement

The views expressed in this article do not represent those of the HEI or its sponsors.

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1
Forest plot of study-specific estimates of relative risk (RR) of lung cancer associated with a 10-μg/m3 increase in exposure to NO2. The meta-estimate and weights in the forest plot are estimated from random effects meta-analyses.
Figure 2
Figure 2
Funnel plot of study-specific estimates of the relative risk of lung cancer associated with a 10-μg/m3 increase in exposure to NO2. The meta-estimate represented by the vertical solid line of the funnel plot is based on a fixed-effects meta-analysis. Fixed-effects meta-analyses are required to assess the potential for publication bias, and assume that there is no between-study variation.
Figure 3
Figure 3
Forest plot of study specific estimates of relative risk (RR) of lung cancer associated with a 10-μg/m3 increase in exposure to NOx.
Figure 4
Figure 4
Relative risk of lung cancer associated with measures of traffic exposure. Abbreviations: k, 1,000; km, kilometers; m, meters; v, vehicles; vkm, vehicle kilometers.
See this image and copyright information in PMC

References

    1. Abbey DE, Nishino N, McDonnell WF, Burchette RJ, Knutsen SF, Beeson WL, et al. Long-term inhalable particles and other air pollutants related to mortality in nonsmokers. Am J Respir Crit Care Med. 1999;159:373–382. - PubMed
    1. Beelen R, Hoek G, van den Brandt PA, Goldbohm RA, Fischer P, Schouten LJ, et al. Long-term exposure to traffic-related air pollution and lung cancer risk. Epidemiology. 2008;19:702–710. - PubMed
    1. Beeson WL, Abbey DE, Knutsen SF. Long-term concentrations of ambient air pollutants and incident lung cancer in California adults: results from the AHSMOG study. Adventist Health Study on Smog. Environ Health Perspect. 1998;106:813–822. - PMC - PubMed
    1. Bellander T, Berglind N, Gustavsson P, Jonson T, Nyberg F, Pershagen G, et al. Using geographic information systems to assess individual historical exposure to air pollution from traffic and house heating in Stockholm. Environ Health Perspect. 2001;109:633–639. - PMC - PubMed
    1. Benbrahim-Tallaa L, Baan RA, Grosse Y, Lauby-Secretan B, El Ghissassi F, Bouvard V, et al. Carcinogenicity of diesel-engine and gasoline-engine exhausts and some nitroarenes. Lancet Oncol. 2012;13:663–664. - PubMed

LinkOut - more resources