Smoking is hazardous to our health. It’s also the leading cause of preventable death in the United States, according to the CDC. And from a public health perspective, there is no doubt that cigarette smoking increases the risk of heart disease, stroke and cancer.

What about secondhand smoke, however — is it similarly dangerous or just an annoyance? A recent article in Slate examined the association with some surprising results.

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The dangers of secondhand smoke first “debuted” in 2003 in an unlikely place, the small city of Helena, Montana. The city instituted a public smoking ban, which a judge overturned six months later. During the short period of the ban, however, the heart attack rate in Helena dropped 60 percent, only to normalize when the ban was lifted.

That was it. The science was settled. The New York Times proclaimed that “secondhand smoke kills.” The rest is history. Towns and cities across the U.S. banned smoking, first in bars and restaurants, then in all public venues.

Subsequent studies failed to replicate the dramatic results of Helena, however, despite a general common-sense understanding that breathing in smoke-infiltrated air from others couldn’t possibly be considered  healthy. Confounding variables were addressed after the fact, including that Helena is a small city, less than 70,000 residents at the time. Heart attacks don’t occur in a steady fashion, such as a set number each week. They can cluster. They are caused by many underlying conditions and risk factors.

Low-fat diets were recommended for decades until it turned out that these diets, high in carbohydrates, were dramatically increasing the incidence of type 2 diabetes.

Larger studies were undertaken, and they found no statistically significant association between heart attacks and secondhand smoke. Some of these studies were done on larger population groups, such as the country of New Zealand and the state of Colorado — where no relation was observed. Ironically in New Zealand, hospitalizations for heart attacks increased after their public smoking ban.

Science is replete with other examples of settled science, which then turn out to be unsettled. Low-fat diets were recommended for decades until it turned out that these diets, high in carbohydrates, were dramatically increasing the incidence of type 2 diabetes. Today butter and animal fats are not considered the killers they used to be and indeed may be good for us, within reason, of course.

Global warming, now called climate change, is another example. Melting ice in one part of the globe becomes de facto evidence of global warming, despite increasing ice levels in another part of the world. Like Helena and smoking, unseasonably warm temperatures in the Midwest and East in February must mean the planet is warming — while major snowstorms and cold temperatures of the week before are ignored.

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Good science requires formulating a hypothesis, followed by observations and data collection that support or refute the hypothesis. When refuted, the hypothesis needs to be adjusted or thrown out, not ignored as we are seeing in the climate change debate. The recent “pause” in global warming confounded climate change warriors — in response, NOAA changed how it collected ocean surface temperature data to erase the previously noted pause.

I have no problems with smoking bans in public places. As do many others, I find cigarette smoke annoying or irritating, particularly when I’m enjoying a meal, concert or sporting event. Similarly, incessant cell phone use can be bothersome, and its use is discouraged or banned in certain venues.

Related: Pregnant and Still Smoking

But no one should formulate such bans based on junk science — this opens a Pandora’s box of other restrictions. Political discourse is stressful, as recently reported in these pages. Will the public health implications of stress be used to shut down political discussions in public? Will the perceived “anxiety” of being physically near a supporter of President Donald Trump become such a health hazard that such an individual needs to be banned — as has occurred on many college campuses today?

Make no mistake. I’m not extolling the “virtues” of secondhand cigarette smoke (if there are any) or claiming in any way that is benign. Such smoke can aggravate asthma or other respiratory diseases, especially in children. But contrary to what for years was considered settled science, secondhand smoke does not appear to cause heart attacks.

Related: How to Stop Smoking for Real This Time

It is dangerous when science is corrupted to further a political agenda. Eventually the truth rises to the surface — but long after unnecessary regulations and government spending are put in place in an attempt to solve an exaggerated or nonexistent problem.

Brian C. Joondeph, M.D., MPS, is a Denver-based physician and writer.