Public Health

If You Question the Deadliness of Secondhand Smoke, You Might As Well Question the Deadliness of Zyklon B


Writing in the European Journal of Public Health, anti-smoking activists Pascal Diethelm and Martin McKee liken people who question the health hazards of secondhand smoke to people who do not believe HIV causes AIDS, people who think the world was created 6,000 years ago, people who are not persuaded that smoking causes cancer, people who maintain that climate change has "nothing to do with man-made CO2 emissions," and people who deny that the Holocaust happened. They say all are dishonest or deluded "denialists," trying to create controversy where there is no legitimate basis for it. Michael Siegel, an anti-smoking activist who agrees that prolonged exposure to secondhand smoke increases the risk of lung cancer and heart disease but questions some of the more extreme claims made by smoking ban advocates, likens Diethelm and McKee to religious fanatics. He has a point:

Diethelm and McKee have endangered the integrity of public health by comparing those who challenge the conclusion that secondhand smoke causes heart disease and lung cancer with those who deny the Holocaust. As a primarily science-based movement, public health is supposed to have room for those who dissent from consensus opinions based on reasonable scientific grounds. To argue that those who fail to conclude that the small relative risk for lung cancer of 1.3 among persons exposed to secondhand smoke is indicative of a causal connection are comparable to Holocaust deniers is to turn public health into a religion, where the doctrines must be accepted on blind faith to avoid being branded as a heretic.

While I personally believe the evidence is sufficient to conclude that secondhand smoke causes heart disease and lung cancer, there are a considerable number of reputable scientists who have come to different conclusions. While I believe those scientists are wrong, I would never argue that they are denialists, nor would I ever compare their dissent with Holocaust denial.

Diethelm and McKee appear to be basing their assessment that secondhand smoke "dissenters" are "denialists" not on the reasonableness of the scientific arguments, but on the position of these arguments. This is a dangerous proposition which threatens the integrity of public health by turning it into a purely ideological movement, rather than a scientific one.

Clearly, no dissent is allowable from the doctrines of tobacco control in Diethelm's and McKee's perspective. This perspective brands hundreds of reputable scientists throughout the world as denialists, no different from Holocaust deniers. While I disagree wholeheartedly with these scientists, I will stand up for their right to express their dissenting opinions without having their characters assassinated because of the direction, rather than the scientific reasonableness, of their positions.

In reply, Diethelm and McKee reject Siegel's analogy while hanging on to theirs, saying they are not advocating censorship of denialists. Of course, Siegel never said they were. Instead they are advocating branding, ad hominem attacks, and blithe dismissal. Diethelm and McKee say "the normal academic response to an opposing argument is to engage with it, testing the strengths and weaknesses of the differing views, in the expectations that the truth will emerge through a process of debate." But this is not possible with denialists, they say, so real scientists (the ones who agree with Diethelm and McKee) should "shift the debate from the subject under consideration, instead exposing to public scrutiny the tactics [the denialists] employ and identifying them publicly for what they are."

We get an idea of what this means in practice from Diethelm and McKee's speculation about the motivations of people who disagree with them:

For some it is greed, lured by the corporate largesse of the oil and tobacco industries. For others it is ideology or faith, causing them to reject anything incompatible with their fundamental beliefs. Finally there is eccentricity and idiosyncrasy, sometimes encouraged by the celebrity status conferred on the maverick by the media.

Might a sincere difference of opinion about what the evidence shows play a role as well? Not when you're dealing with denialists.

Speaking of science distorted by "ideology or faith," Diethelm and McKee say one of the tactics employed by denialists is "inversionism, in which some of one's own characteristics and motivations are attributed to others"—a wonderful demonstration of inversionism as well as a definition. Diethelm and McKee display a similar lack of self-awareness when they note with distaste that "pro-smoking groups have often used the fact that Hitler supported some antismoking campaigns to represent those advocating tobacco control as Nazis." This comes one page after they compare secondhand smoke skepticism to Holocaust denial.

Another indication of Diethelm and McKee's M.O. is their reference to a 2003 British Medical Journal study that found no association between secondhand smoke exposure and lung cancer or heart disease. They say the study was "later shown to suffer from major flaws, including a failure to report competing interests." This (false) insinuation that the authors of the study, James Enstrom and Geoffrey Kabat, had a financial stake in the outcome is the only "flaw" Diethelm and McKee cite. A "failure to report competing interests" is not a methodological weakness, and it does not in any way invalidate a study. That requires showing that there were serious problems with the way the researchers collected or analyzed their data. Except when you're dealing with denialists.

On his blog, Siegel discusses another journal article whose authors assert that failing to agree that smoking bans cause immediate, dramatic reductions in heart attacks is enough to put you on par with "the self-styled AIDS dissidents who continue to deny the causal link between HIV and AIDS."

[via The Rest of the Story]