Passive Smoking and Cancer: Fact or Fiction?

James Stark, MD, of Stark Oncology

James Stark, MD, of Stark Oncology

As an Oncologist, for years I believed that passive smoke – that inhaled when you don’t smoke but those around you do – was overhyped as a health risk.  After all how could your exposure to smoke second hand compare to that received by someone inhaling a cigarette directly into his or her lungs?  And then I looked into it further.

I started with a recent article in the British Medical Journal (BMJ 2011;342:d1016) which re-ignited the debate about the role of passive smoking and cancer.  For a long time conventional wisdom held that there was no relationship between smoking and breast cancer.  The Women’s Health Initiative (WHI) – the same group that killed off hormone replacement therapy by its findings about hormones, cancer and heart disease – has now weighed in on the relationship of smoking and breast cancer. Brainchild of the Harvard School of Public Health, the WHI is one of several groups conducting huge longitudinal studies carried on over decades to try to understand what causes diseases, and how they can be prevented. In the British Medical Journal article the HSPH has told us what they learned by studying nearly 80,000 women over many years.

What is the risk of passive exposure to cigarette smoke?
Long-term smokers had a 35% higher incidence of breast cancer than women who never smoked.  Among women who never smoked but who had long-term high intensity passive exposure to cigarette smoke (in childhood, as adults at home and at work – all three) there was an increased risk of 32% for getting breast cancer compared to women who had no exposure to passive smoke – a difference that was almost as significant as that seen with actual smokers.  This result was stunning both in its magnitude and its surprise value.  Most scientists had written off the relationship of smoking and breast cancer.

The evolution of the knowledge of harm from passive smoke is rich with carefully controlled trials.  Several earlier large epidemiological studies showed a remarkably consistent risk for the development of lung cancer in people who lived in close proximity to smokers. There is roughly a 20 to 30% increased risk of lung cancer among people who never smoked if they were exposed to second-hand smoke: the more intensive the exposure, the higher the risk.  The other major disease at risk is coronary heart disease, where exposure to second-hand smoke is thought to cause 40,000 extra and preventable deaths per year. The risk of dying of a heart attack if you live with a smoker is likewise 20-30% higher than if you did not. Banning smoking in public places, especially the work place, has resulted in a lower but significant risk reduction of acute heart attack (Journal of the American College of Cardiology. 54(14):1249-55, 2009).

What can you do to improve the situation in a home in which someone smokes?
Studies have shown that most efforts at cleaning the air are futile.  Air filters do not work.  Current efforts at improving insulation in the home to conserve energy actually make retention of smoke more of a problem.  Restricting smoking to one room isolated from the rest of the house and postponing smoking until after children have gone to bed (to protect them, if not the spouse) are considered the most practical interventions, and are somewhat effective.

Fortunately the incidence of smoking in the US is at an all-time low. Worldwide, however, it is estimated that one billion people are active smokers.  The problem of passive smoke in countries like China, where smoking is pervasive, remains huge.

When the damage from passive, or second-hand, smoke was first discovered, the cigarette industry led a campaign of disinformation to try to discredit published scientific trials.   After the Justice Department got wind of this they sued the industry.  A US Federal Court found the industry guilty of fraud and racketeering (Judge Gladys Kessler, in US v. Philip Morris, civil action 99-2496, 2006),

Now that breast cancer has been added to the list of diseases preventable by smoking cessation the need to stop exposure to cigarette smoke has become even more compelling.  Public awareness has accomplished what could not be done with legislation – reducing the amount of cigarette smoking in the United States.  There is, however, much more to be done.

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