There is strong and consistent evidence that exposure to secondhand smoke causes heart attacks and that smoke-free workplace and public place laws cut heart attacks (and other diseases). The most recent evidence comes from a large study in Sao Paolo, Brazil, where heart attack deaths dropped by 12 percent following implementation of its smoke-free law. The Conversation

Even so, we still hear people challenging the science. For example, a recent article by a onetime employee of the tobacco industry-supported Cato Institute and bartender, tries to use the natural variability in results in different studies to argue against this fact.

This is the latest echo of more direct attacks that the tobacco companies have mounted since the 1970s, when the evidence that secondhand smoke caused disease started accumulating. For decades as the evidence that secondhand smoke kills became stronger and more consistent, the media continued to quote people with tobacco industry ties, which made the science appear increasingly controversial rather than settled.

The cigarette companies themselves are now prohibited from challenging the established science by Judge Gladys Kessler’s landmark ruling in 2006 that the big cigarette companies defrauded the public violated the Racketeer and Corrupt Influenced Organizations Act (RICO) by sowing confusion about the dangers of smoking and secondhand smoke.

But that hasn’t stopped “third parties” from questioning the science.

Similar to the recently published 2017 article, in 2013 Forbes published an article by a financial and legal reporter entitled “Study Finds No Link Between Secondhand Smoke And Cancer.” The article ignored the fact that the US Surgeon General concluded secondhand smoke caused lung cancer in 1986 and that the U.S. Environmental Protection Agency concluded it was a “Class A” human carcinogen in 1991.

The actual study on secondhand smoke and lung cancer, however, found that women living in the same house with a smoker for 30 years or more had 60 percent higher odds of developing lung cancer. The certainty of this statement was only 95 percent! (Statisticians like to be more than 95 percent confident to call the effect “statistically significant”.) Like the attack on the heart attack studies, the Forbes piece ignored the larger body of evidence.

I have spent my professional life in tobacco control and have seen these tricks for decades, so understand why it is so important to pay attention to all the evidence.