Deskundige uit twijfel over echte risico meeroken
Tijdens een hoorzitting die in februari van dit jaar ter voorbereiding van de besluitvorming rond het Engelse rookverbod in het Hogerhuis werd gehouden, werd onder andere Sir Richard Peto ondervraagd over de risico’s die mensen zouden lopen bij meeroken. Wat opvalt is de uitermate grote voorzichtigheid waarmee deze beroemde Engelse anti-rokenexpert en epidemioloog de vragen van de lords beantwoordt. In feite ontwijkt hij stellige uitspraken, geeft hij ronduit toe dat dit risico niet is in te schatten en dat het terrein van meeroken vol ligt met politieke voetangels.
Op de laatste vraag die aan hem gesteld werd (“You have been unwilling to quantify the risks from passive smoking?”) antwoordt de geleerde met een heel simpel “Yes“.
De getuigenis van Dr. Richard Peto was aanleiding voor twee andere geleerden, Enstrom en Kabat, om in het British Medical Journal de anti-rokerswereld het nog eens in te wrijven:
“Sir Richard’s testimony is direct evidence that there is substantial doubt in the mind of a preeminent epidemiologist about the quantitative health risks of passive smoking. Hopefully, this fact will help contribute to rational and objective evaluation of the health risks of passive smoking.“
Een onderzoek dat beide wetenschappers enige jaren in het BMJ publiceerden, waarin ze ook duidelijk stelling namen tegen de meerokenleugen, leverde hun een storm van kritiek op uit het anti-rokenkamp.
Lord Macdonald of Tradeston: Sir Richard, I wanted to start by asking if you could give us your assessment of the health risks associated with passive smoking and how those risks compare with passive smoking in the home or at work and in other public places. It would be helpful if you could give us an indication of both absolute and relative magnitudes of the health risks and also the degree of uncertainty attached to the available statistical evidence.
Professor Sir Richard Peto: I am sorry, I know that is what you would like to be given, but the point is that these risks are small and difficult to measure directly. What is clear is that cigarette smoke itself is far and away the most important cause of human cancer in the world – that is, cigarette smoke taken in by the smoker – and passive smoking, exposure to other people’s smoke, must cause some risk of death from the same diseases. Measuring that risk reliably and directly is difficult. You can do it indirectly by suggesting approximate proportionality of hazard to exposure, but the assumptions become almost untestable. The arguments that have been forward for the various thresholds, that there is some sort of dose below which there is absolutely no risk, have really no scientific plausibility. They have come up a lot of times because, as you know, when there is the statement “there is some risk” then there is the political pressure to get rid of that risk, and so it would be very convenient if one could be told that there was no risk, and so various implausible models involving thresholds got proposed. There is going to be some risk and there is always going to be quite a lot of uncertainty about the magnitude of that risk, I am sorry. What is definite is that cigarette smoke is causing about 100,000 deaths a year in this country, a few million deaths a year worldwide and this number of deaths is still increasing in other countries, although not in this country, and that exposure to cigarette smoke in various circumstances must be producing some risk. That is definite, that is clear, and the threshold arguments are often politically motivated inventions which actually do not have much scientific plausibility. I am sorry not to be more helpful; you want numbers and I could give you numbers by direct extrapolation, but what does one make of them? These measures cannot be directly measured.
Q382 Lord Macdonald of Tradeston: If you have such a large sample of people dying of lung cancer, would it be possible to interview them about their personal circumstances in a way that would allow you to deduce whether they had frequented bars or had a smoky home or whatever?
Professor Sir Richard Peto: This has been done. People who smoke cigarettes persistently have about 20 times the lung cancer risk of those who never smoke; that is a 2000 per cent excess. The exposure that one would get when breathing other people’s smoke obviously depends on the circumstances, but even heavy exposure would be something like one per cent of what a smoker gets, maybe in other circumstances 0.1 per cent, so you would expect if there was just proportionality to get something of the order of 20 per cent excess. That is what you see in the average of all the studies, and people have pointed to the uncertainties – it could under-estimate the real hazards, it could over-estimate the real hazards. It is roughly what you would expect from simple proportionality.
Over Enstrom en Kabat: