et%. 1.
    f
    REVIEW 616 CONFIDENTIA
    --Subi ect-jef 8a
    "A Popperian approach to the passive smoking issue"
    C La Vecchia
    International Journal of Cancer (1992), 51, 159
    This short letter, from a well-known and prolificItalian
    epidemiologist, may be important, even if it lacks logic.  It makes an
    19 argument (also projected by Dr Lippmann, Chairman of the Scientific
    Advisory Board of the EPA group on ETS, at a recent meeting in
    Washington) that because smoking is associated strongly,with cancer, and
    because carcinogens in ETS are the same as those in mainstream smoke, we
    must accept passive smoking causes cancer until epidemiology proves
    conclusively that ETS is not associated with an elevated risk of lung
    cancer.
    The problem with the whole argument, of course, is that it is
    imvossible to prove a negative. Even if one could randomly assign
    subjects to be exposed or not to ETS, and observed a relative risk of
    lung cancer of 1.00, the upper 95% confidence limit will exceed 1.00
    (unless the study is of infinite size), so a negative is not proved. A
    more logical approach, along the same lines, would be to say "Lec: us
    assume a risk unless it can be demonstrated the risk is less than some
    defined small amount". Even then proving say a relative risk is less
    than 1.05 is almost impossible in practice epidemiologically. U1
    C)
    CD
    00
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    BATCo document for Legal Services : Health Canada 19 October 1999

    




    --~ I,'- AC- C-
    Int. 1. Cancer $1. 159 (19921 poc~~%G rur~ nerrwoo~*Conav * C4ncso
    C 1972 Wilcy-Liss. Inc.
    LETTER TO THE EDITOR
    Dear Sir,
    A Popperi an apprcacb to the passive smoking Issue
    7he evidence that tobacco smoking causes lung cancer is To disprove the jhyporhesis~ epidemiology should provide
    overwhelming. we have epiderniolvecal data showing a strong convincing and conclusive evidence Lhatpassive smoking is not
    =ociadon between sprto;dng and cancer, we know that cg"- associated uith elevated risk of lung cancer. In the absence of
    sure so tobacco causes cancer in animal esperimenis, and such evidence, we have to accept that passive smoking is
    smoke condensate contains several carcinogens (MRC, 1986; indeed carciwgenic to h urnarts.
    US DHHS, 19891. Yours sinceret
    Exposure to environmental tobacco smoke, orpassile smok-
    ing, entails exposure to the same carcinogens, although their CarlOL4 VECCHL4
    leveis a. e substantiallf lower and their composition Is propor- Istituto di Ricerche Farmacologiche "Afario Negri". Milan,
    tionally different (US DHHS, 1986). ne application of "Pop- Italy. and Instirut Universitatre de Afidecirte 50ciak et Priven-
    -s cardinal precept that refutation is heurisrical~- more rive, Lausanne, Switzerland
    ,awerfid than corifirmazion" (Buck 1975) to this issue ap-
    pears therefore reasonable, assuming as a testing kspothesis
    that passive smoking is carcinogenic to humans. December 11. 1991.
    REFERENCES
    BucK. C, Popper's philosophy for cpiderniologists. Int. 1. Eptdemioi., 4. SeRvicE. 77te Susycon Gcncroi*s 1989 Reporr on reducutg 
    rhe healih
    159-168 (1915). consequences ofsmoAdng: 25 years q(progress. GPO. Washington (1989).
    LARC. Ealuarion f h . Uk of chemicals 10 humans- US DEPARTmEmT OF HEALTH AND HUMAN SERVICES. PUSUC HEALTH
    n C "'
    '~,ca '09' c
    tobacco jmoAdrg. L49C -,;.p . ~01_39, [ARC. Lyon (1956). SERVICE. The health conscouencei ofinvoluMaj.1 kin 0
    ysmo garepmq[the
    US DErARrmE.,:,. OF HEALT14 AND HUN" SERVICES. PUBLIC HEALTH Surgeon Generak Me& CPO, Washington (1986).
    (-:D
    C.0
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    BATCo document for Legal Services : Health Canada 19 October 1999