De passief roken mythe

The alleged dangers of second-hand tobacco smoke, also known as Environmental Tobacco Smoke, or ETS for short, represents junk science’s biggest success story. Ever since the U.S. Environmental Protection Agency decided 10 years ago that ETS caused cancer in nonsmokers, the ETS junk science juggernaut has been unstoppable. Most of us now believe that ETS is dangerous and virtually all of us live out our public lives — working, shopping, eating, in smoke-free environments.

But the ETS junk science crusade encountered a major and unanticipated setback a few weeks ago when the British Medical Journal published a study by two U.S. researchers that found no statistically significant association between not only ETS and lung cancer but also between ETS and heart disease.

The study focused on 35,561 Californians who never smoked but had smoking spouses. The participants were all part of the massive American Cancer Society cancer prevention Study (CPS 1) and their lives and deaths were followed from 1960-1998. The relative risks for never-smokers married to smokers was 0.94 for coronary heart disease and 0.75 for lung cancer. Unlike the government reports cited by junk scientists as proof that ETS causes lung cancer and heart disease, this study is not a meta-analysis — a combination of individual studies to create a pooled result) — or a so-called “consensus statement” by hand-picked experts. It is an original, primary study of ETS. As the authors note “none of the other cohort studies … has more strengths, and none has presented as many detailed results.”

To anyone who has followed the scientific literature on ETS, as opposed to the anti-smoking movements, statements and government pronouncements, this study should come as no surprise. For one thing, the pattern of study results has been unchanged since the first studies in the 1980s. Over the 20-odd years of ETS studies, some 60 studies have reported results similar to this one, finding no statistically significant association between ETS and lung cancer. Of the 11 studies that have found a statistically significant association, none has reported an overall strong relative risk. This is particularly telling since epidemiological studies of real as opposed to phantom risks are usually weak at first but gain strength and clarity with time. The ETS studies have continued to be equivocal.

The only way in which the “case” against second-hand smoke has been made is through the highly controversial use of meta analysis in which individually inconclusive studies have been pooled to produce statistically significant relative risks. This is the way in which every major government report on the alleged dangers of ETS has been created. The logic here is that if you put 10 leaking buckets together, they might just hold water. Unfortunately, this hasn’t worked, for however hard you pound the data the relative risk for ETS and lung cancer and heart disease just won’t rise beyond about 1.50, a relatively insignificant level.

Ironically, this study should come as no surprise because it confirms the WHO’s own large 1998 ETS study spanning 10 years and involving 12 cities in seven European countries. The WHO study found no statistically significant increase in lung cancer risk for nonsmokers exposed to ETS in childhood settings, workplace environments and homes. Of particular interest for the ongoing Canadian debate about smoking in restaurants and bars is the fact that WHO found such smoking did not result in a statistically significant risk of lung cancer for non-smokers.

In a sane world, sans junk science, one would expect that after 20 years of failing to find a significant risk from ETS, the game would be over. But the strength of junk science comes not from the power of its evidence but rather from the fervency of its believers and their willingness to do virtually anything to silence dissent. Indeed, the weaker the evidence the stronger the belief. There is no room for dissent in the church of junk science; unbelievers face the stake just as surely as the medieval heretic.

Even before the release of the British Medical Journal article, the anti-smoking movement was in high attack mode, denouncing the study as funded by the tobacco industry. Former U.S. surgeon general Julius Richmond was pulled out of retirement to muse that, “This study is just the latest in a long string of studies designed to deny the evidence and confuse the public. The first study linking second-hand tobacco smoke and lung cancer was published 22 years ago when I was surgeon general, and the evidence has only become stronger since then.” Perhaps the good doctor is a bit confused, for the evidence has been remarkably consistent in not linking ETS and cancer and it has not become stronger with time. The first ETS study to which Dr. Richmond refers did not find a statistically significant association between ETS and lung cancer. Ironically, the author of that study is thanked by authors Enstrom and Kabat for his help in making their study successful.

So successful has been the junk science counterattack that virtually every major story on the study has concentrated on the fact that one of the authors has received funding from the tobacco industry, rather than on the merits and findings of the study itself. The peculiar and effective pathology of junk science is thus on full display: Deny or downplay the results and instead attack the character of the researcher. What makes this strategy so transparently loathsome is that Prof. Kabat is a well-known expert on cancer and has carried out previous ETS studies that no one has attacked.

After 20 years of failing to link ETS with significant heart and lung disease, one would think that it is time to call it quits on public smoking bans, or at least to acknowledge they have nothing to do with health but merely with the desire to avoid the nuisance of second-hand smoke. One might even think that an apology, however grudging, might be offered up by various governments to the six million smokers of Canada who have been portrayed as recklessly endangering the health of their families, friends and co-workers.

None of this will, of course, happen for the ETS junk science crusade, like all junk science campaigns, has nothing to do with science but everything to do with manipulating the public’s perception of reality for ideological ends.

John Luik, a consultant in the health field, is the coauthor of Passive Smoke: The EPA’s Betrayal of Science and Policy. Some of his ETS research has been supported by the tobacco industry