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Challenging the epidemiologic evidence on passive smoking: tactics of tobacco industry expert witnesses


Objective: To analyse the statements given by tobacco industry defence witnesses during trial testimonies and depositions in second-hand smoke cases and in parallel, to review criticisms of epidemiology in industry-funded publications in order to identify strategies for discrediting epidemiologic evidence on passive smoking health effects.

Methods: A collection of depositions and trial testimony transcripts from tobacco industry-related lawsuits filed in the United States during the 1990s, was compiled and indexed by the Tobacco Deposition and Trial Testimony Archive (DATTA). Statements in DATTA made by expert witnesses representing the tobacco industry relating to the health effects of passive smoking were identified and reviewed. Industry-supported publications within the peer-reviewed literature were also examined for statements on exposure misclassification, meta-analysis, and confounding.

Results: The witnesses challenged causation of adverse health effects of passive smoking by citing limitations of epidemiologic research, raising methodological and statistical issues, and disputing biological plausibility. Though not often cited directly by the witnesses, the defence tactics mirrored the strategies used in industry-funded reports in the peer-reviewed literature.

Conclusion: The tobacco industry attempted to redirect the focus and dialogue related to the epidemiologic evidence on passive smoking. This approach, used by industry experts in trial testimony and depositions, placed bias as a certain alternative to causation of diseases related to passive smoking and proposed an unachievable standard for establishing the mechanism of disease.

  • CIAR, Center for Indoor Air Research
  • DATTA, Tobacco Deposition and Trial Testimony Archive
  • EPA, Environmental Protection Agency
  • ETS, environmental tobacco smoke
  • IARC, International Agency for Research on Cancer
  • NHANES, National Health and Nutrition Examination Survey
  • ORNL, Oak Ridge National Laboratory
  • OSHA, Occupational Safety and Health Administration
  • tobacco industry
  • passive smoking
  • environmental tobacco smoke
  • ETS
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