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air pollution and lung cancer

A paper published in The Lancet Oncology found prolonged exposure to particulate air pollution increases the risk of lung cancer, even at levels below the European Union limit values. This before the headlines analysis accompanied a roundup.

 

Title, Date of Publication & Journal

Air pollution and lung cancer incidence in 17 European cohorts: prospective analyses from the European Study of Cohorts for Air Pollution Effects (ESCAPE)

9 July 2013

Lancet Oncology

 

Claim supported by evidence?

The paper provides evidence that particulate matter air pollution contributes to lung cancer incidence in Europe.

 

Summary

  • The key finding after combining 17 large cohort studies together and allowing for major confounders such as smoking and socioeconomic status was marginally significant (95% confidence interval for was 1.03 -1.45 per 10 μg/m3). A difference of 10 to 20 μg/m3 is typically seen between major European cities with southern Europe most polluted.
  • The results from within the 17 cohorts were consistent with each other (no evidence of heterogeneity) adding support to the veracity of the conclusions.
  • Smoking remains a much more important risk factor for lung cancer. Indeed controlling for the impact of smoking is one of the crucial aspects of this study’s analysis. Those living with more air pollution were smoking more.

 

Study Conclusions

  • The analysis within each cohort compared every individual subject’s own air pollution experience (as modelled based on exact residential location) to their lung cancer status.
  • Current air pollution levels are now lower than at the time when these subjects were at risk (recruited in the 1990’s).

 

Strengths/Limitations

  • A meta-analysis of 17 European prospective cohorts with varying levels of pollution and location.
  • Each cohort was carried out using the same protocol and analysed separately using the same strategy.
  • Careful modelling of air pollution concentrations allowed within cohort analyses to identify pollution levels at the individual subject level.
  • Results remain statistically significant after adjusting for important covariates including smoking and socioeconomic factors (model 3).
  • Missing data were ignored, but this is unlikely to have had a major impact.
  • Several reasonable alternative mechanisms are suggested for an association with ambient air pollution.

 

‘Before the headlines’ is a service provided to the SMC by volunteer statisticians: members of the Royal Statistical Society (RSS), Statisticians in the Pharmaceutical Industry(PSI) and experienced statisticians in academia and research.  A list of contributors, including affiliations, is available here

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