A comprehensive list of passive smoking and lung cancer studies

Peter Lee is an Oxford educated statistician who has consulted to pharmaceutical and tobacco companies. Here is a list of 80 studies into passive smoking and lung cancer. He concludes:

“The overall evidence shows no statistically significant increased risk of lung cancer in relation to ETS exposure from parents in childhood, or in social situations, or to nonspousal ETS exposure at home.

The overall evidence shows that lung cancer risk among nonsmoking women is  significantly associated with having a husband who smokes (with a similar association seen in nonsmoking men  in relation to smoking by the wife, though based on far less data).

There is also evidence of a dose-response relationship,   with risk higher if the husband  smokes more cigarettes per day or for a longer period of time.  However, there are a number of reasons why this association and dose-response relationship cannot be interpreted as indicating a causal effect of ETS exposure including:

• the association is weak and is not statistically significant in the great majority of studies: over 80% show no statistically significant association between smoking by the husband  and the development of lung cancer;

• the combined results vary over time, with the association being significantly weaker in  the studies published from 1990 than in those published in the 1980s;

• some of the very largest studies show no association, including four of the five studies involving over 400 lung cancer cases.  One  of these reported no statistically significant  association between lung cancer and any index of ETS exposure, while another  even  reported a statistically significantly reduced risk of lung cancer for non-smoking women  married to smokers;

• almost 20% of the studies have not adjusted for age in the analysis, a standard procedure  in epidemiology to avoid bias.  These studies report much stronger associations with  spousal exposure than are reported by studies that did use age-adjustment.   • spousal studies are particularly susceptible to various biasing factors.  These include:

i) failure to consider diet, lifestyle, family medical history, education, socio-economic  status and other factors believed to differ between smoking and non-smoking  households; and

ii) the inappropriate inclusion of some misclassified current and former smokers  among the lifelong non-smokers.

• reliance on reported rather than objectively measured ETS exposure data, and failure to publish negative studies.

No-one has yet designed a study in such a way as to eliminate all these sources of bias.  Analyses published in 2000-2002 demonstrated formally that the weak association and dose-response relationship between lung cancer and  smoking by the husband would essentially disappear were proper adjustment made for age, diet, education and misclassification of smoking habits, a conclusion confirmed based on more recent data.

There is also some indication from the overall evidence that lung cancer risk among nonsmokers might be weakly associated with workplace ETS exposure.  However, only seven of 39 relative risk estimates are statistically significant and biases that apply to the spousal data are also likely to apply to the workplace data.

There is similarly weak evidence of an association with overall childhood ETS exposure.  Here the five largest studies give risk estimates below 1, but several of the moderate size studies report an increased risk.

http://www.pnlee.co.uk/documents/refs/lee2010B.pdf

Taken as a whole, the epidemiology does not support the claim that ETS causes lung cancer in non-smokers.

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3 Responses to A comprehensive list of passive smoking and lung cancer studies

  1. Dawn says:

    I have been saying this to people who complain and moan about the dangers of passive smoking for years but you just cannot compete with the indoctrination which has been done through the mainstream media :(.
    I was a smoker for many years and I stopped nearly 3 years ago. I just thought it might help my breathing, I cough less but I don’t breath any better, in fact the stress levels are worse and my husband is substantially worse in health since he stopped smoking. Weird isn’t it?
    I know for a fact that many who stop smoking notice a negative effect on their thyroid function.
    take care
    Ladydawn

  2. Anton says:

    Unlike Dawn above I have been a lifelong non-smoker except for a few months in my early teens when I never inhaled anyway. I simply never ‘got it’ and still don’t understand the pleasure people get from smoking; but they do get something it’s clear.
    The bad news is that it kills one in four prematurely and those are rotten odds.
    Yes it smells a bit for us that don’t smoke but it does not bother me that much. What does bother me is the lies put out about exhaled smoke being harmful to others, It seems to me that this campaign against passive smoking is the start of state control of peoples own lives using junk science when real science keeps informing us that ETS is harmless in the great shape of things.
    I am very much more aggravated and fearful having my life manipulated by zealots than ETS anytime.

  3. Sallie says:

    Absolutely love all these steam showers

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