To the contrary, many of the studies cited as bomb-proof evidence for the public dangers of secondhand smoke have been heavily criticized for years. What is really interesting is the role that tradition (presuppositions received from the past and present medical communities) played in influencing the studies’ findings. In each case, the unintentional bias toward a particular result created blind-spots that undermined the value of the findings.

This article over at Slate about the bad science that led to many anti-secondhand smoke policies provides some inconvenient truths about the role of tradition and confirmation-bias in what we might call public science (those scientific debates that are fought in the arena of public opinion, usually because of direct policy implications).

I personally prefer the resulting smoke free-zones that, thanks to many of these policies, have multiplied around the U.S., but that doesn’t mean their existence is necessitated by hard science. To the contrary, many of the studies cited as bomb-proof evidence for the public dangers of secondhand smoke have been heavily criticized for years.

What is really interesting is the role that tradition (presuppositions received from the past and present medical communities) played in influencing the studies’ findings. In each case, the unintentional bias toward a particular result created blind-spots that undermined the value of the findings.

In the paper’s admirably honest commentary, the authors reflected on the reasons that earlier studies, including their own, had overstated the impact of smoking bans. The first is that small sample sizes allowed random variances in data to be mistaken for real effects. The second is that most previous studies failed to account for existing downward trends in the rate of heart attacks. And the third is publication bias: Since no one believes that smoking bans increase heart attacks, few would bother submitting or publishing studies that show a positive correlation or null effect. Thus the published record is likely unintentionally biased toward showing a larger effect than truly exists.

Where heart attacks did decline, it may not have even been because of secondhand smoke reductions.

The medical reasoning behind why secondhand smoke would cause heart attacks posited that short-term exposure reduces blood flow, increases platelet aggregation, and causes endothelial dysfunction—all of which could increase the risk of heart attack. But looking at the most well-conducted research suggests that the actual impact is not as significant as originally feared. And where heart attacks did decline, it may not have even been because of secondhand smoke reductions: A new paper published in August 2016 considered other factors that may have been overlooked. Drawing on data from 28 states from 2001–2008, lead author Vivian Ho, an economist at Rice University, compared rates of hospitalization for heart attacks in areas with and without smoking bans.

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