Some things are hard to believe, like a prediction that Martians will land in Atlanta tomorrow.
Even harder to accept is the fact that some folks, including people in positions of substantial responsibility -- such as mayors, governors and other politicians -- don't believe that exposure to secondhand smoke is harmful.
It is. The evidence is very clear that exposure to secondhand smoke can cause illness and death.
Despite all of that evidence, we still seem to have barriers in place that prevent us from enacting laws that would protect those of us who are non-smokers (and I would also include former smokers) from the harmful effects of environmental tobacco smoke.
One remaining issue regarding the harms of secondhand smoke has been the question of how much lung cancer risk exists for non-smokers who are exposed to secondhand smoke in the workplace.
A study reported today in the American Journal of Public Health answers that question and takes us one step closer to understanding how dangerous secondhand smoke can be.
As the authors point out, most research on the topic of secondhand smoke and the risk of developing lung cancer has been done with the non-smoking spouses of smokers.
Where we don't have a clear picture is the lung cancer risk you face if you are a non-smoker and work in a place that permits smoking. For many folks, that means in restaurants, bars and casinos, among other locations.
To answer this question, the researchers examined a number of scientific papers published on the topic of lung cancer risk and secondhand smoke in the workplace.
They took the information from those papers and pooled the numbers so they could get an idea of whether non-smoking workers in those workplaces faced an increased risk of getting lung cancer.
The answer, simply stated, was "Yes."
When combining all of the papers and all of the subjects studied as part of those 22 reports, the researchers found there was a 24 percent increased risk of developing lung cancer in non-smoking employees who were exposed to secondhand smoke in the workplace.
However, they also noted that if you were a worker considered to be "highly exposed" to environmental tobacco smoke at work, then your risk of getting lung cancer was doubled compared to people who did not smoke.
That may not seem like much. After all, we know that almost all lung cancers are related to cigarette smoking. About 10 percent to 15 percent of lung cancers occur in people who don't smoke.
The chances of any one man getting lung cancer during his lifetime are 1 in 12, and for women, the risk is 1 in 16.
If you are a non-smoker, your odds of getting lung cancer are much less than that.
But, if you work in a smoky bar for a length of time, and you don't smoke yourself, then your chances of getting lung cancer increase significantly, according to this study.
The reason this is such a problem, as pointed out in the article, is that many folks -- even today -- work in smoky places. That means that many folks are at an unnecessary risk of getting lung cancer.
Let's not forget that a diagnosis of lung cancer is no minor issue. Most of the folks with this disease are diagnosed at late stages, and frequently the disease is fatal.
Lung cancer screening with CT scans -- for which the jury is still out for most smokers and former smokers -- isn't even on the radar for people who are non-smokers. That translates into no early signs, no early symptoms and a poor prognosis once diagnosed.
As pointed out in the article, there is a long list of distinguished organizations that all agree on one thing: Secondhand smoke causes cancer in people.
The list includes, among others, the Surgeon General, the National Institute for Occupational Safety and Health, the U.S. Environmental Protection Agency and the International Agency for Research on Cancer.
The American Cancer Society certainly believes that secondhand smoke causes lung cancer, and has worked hard for the passage of strong smoke-free laws nationwide.
Today, 21 states, the District of Columbia and more than 2,500 communities have smoke-free laws in place.
That means that 52.9 percent of the population in the United States is now protected from secondhand smoke.
According to my American Cancer Society colleagues, all top 10 tourist destinations in the United States have some form of smoke-free law.
The impact of smoke-free laws has been studied extensively, especially in New York -- which had the guts to go smoke-free in the face of significant opposition, and made it work. New York serves as an example to any community in this country that thinks people won't support a decision to create a healthy indoor environment.
By many measures -- including economic ones -- the decision by New York to go smoke-free was a huge success.
In fact, as a result, the New York State Department of Health estimates that there are 140,000 fewer smokers in New York today than when the regulation was enacted in 2003.
In June 2006, the Surgeon General produced a report that provided overwhelming evidence that secondhand smoke is a danger to our health.
Beyond causing lung cancer, the Surgeon General noted that secondhand smoke "has immediate adverse effects on the cardiovascular system and causes coronary heart disease and lung cancer."
Despite all that we know, there are still 126 million Americans who are non-smokers (many of whom are children) who are regularly exposed to secondhand smoke.
And so I conclude where I started:
What is it that our elected leaders don't understand?
Why do they continue to pay homage to those who say it is their "right" to smoke?
Why are they so afraid that economies will suffer, when the evidence says that not only will businesses survive, but many have found their revenues increased?
It bears repeating that there are a lot of angry folks out there who agree with former Surgeon General C. Everett Koop, who said, "The right of smokers to smoke ends where their behavior affects the health and well-being of others."
There is no "right" to smoke except in your own private space.
There is no "right" to harm me and my family.
There is no "right" to risk the lives of your workers.
To me, the conclusion of this report is clear: No one should have to pay with their lives for the right to earn a living.
It is time for many parts of this country to take this message seriously, and do the right thing.
Dr. Len Lichtenfeld is deputy chief medical officer for the American Cancer Society. You can view the full blog by clicking here.