Background: A fiercely debated subject of health during the past two decades has been the risk of heart disease and cancer for non-smoking persons that are exposed to the cigarette smoking of others. This is called the risk of "Passive Smoking". This debate was a ‘Last ditch" stand of the Cigarette companies in defense of their product, but a stand that they hopelessly lost The clouds of smoke from smokers permeate any indoor atmosphere, and even that outdoors on a non-windy day. It would be hard to conceive that if this smoke produces major diseases in smokers that it would not similarly produce the diseases in those that breathe this same air. Acceptance of the research that follows here has forced more and more establishments to ban smoking indoors, or at least create non-smoking areas for those that wish to avoid breathing the air polluted by smokers.

The Research: Medline now lists more than 4650 studies relating to the effects of Passive Smoking. The results are convincing and impressive. A meta-analysis or summary average result of 19 studies by Law (BMJ 1997;315:773) found that Passive Smoking produced an average risk ratio for coronary heart disease of 1.30 (CI = 1.22-1.38), and with adjustments was 1.23 (CI = 1.18-1.64). A group from the large MRFIT study showed an average risk ratio of 1.40 (CI = 0.8-2.5). Men who were exposed to co-workers but with wives that did not smoke suffered a 1.2 (CI = 0.4-3.7) and those with wives that smoked and co-workers that smoked had an RR of 1.7 (CI-0.8-3.6). Another meta-analysis of 18 studies on Coronary heart disease by He, (NEJM 1999;340:920) also found an RR of 1.25 (CI = 1.17-1.32). Those exposed to partners smoking 1-19 cigarettes per day had an RR of 1.23, and those exposed to partners smoking 20+ per day had an RR of 1.31. Men and women had similar results.

Similar results were obtained for the risk of cancer. Average all-cancer risk on women was 1.23 (CI = 1.12-1.31) for women whose husbands smoked. A higher value of RR=1.68 (CI = 1.1-2.5) was obtained by Reynolds from the Alameda, CA study. This is a sampling of more that has been published.

From an assessment of this and other evidence, the following risk ratios were adopted for Life Ahead computations: RR=1.0 for no Passive Smoking; 1.13 for a "A little Passive Smoking"; 1.25 for "Average Passive Smoking; and 1.40 for "Much Passive Smoking". These values appear valid for both heart disease and cancer within the accuracy of results available. Note that the harm of Passive Smoking dwarfs that of environmental pollution. As compared with a 40% potential risk from Passive Smoking, the maximum from other usual pollution was only an 8% increase in risk.

The effects of Passive Smoking on disease on specific diseases are somewhat different than those from smoking cigarettes per se. (But this needs more review than has been given here to date). As example, the risk of lung cancer from Passive Smoking was similar to that on all other cancer, and is not a great deal larger as is found for direct smoking. Note that Life Ahead assesses quite different risks of smoking to heart disease and to various causes of cancer. See the discussion on Smoking

Passive Smoking as Represented in Life Ahead: The guide adopted for Life Ahead uses an assumed equivalent in cigarettes per day for heart disease of 1.0 for "Little"; 2.3 per day for "Average"; and 5.0 for "Much" Passive Smoking. The equivalents for all cancer except lung cancer are 3 times higher; those for lung cancer are lower. These values modified somewhat by individual disease to reproduce the actual research results of Passive Smoking. As a worst case, a non-smoker that is exposed to "Much" Passive Smoking will acquire a cancer risk similar to that of a smoker of a dozen cigarettes per day. And exposure at work adds substantially to exposure at home. Risk from cigarette smoke increases with years of exposure, and exposure to passive smoke can be over a full life-time, not just during years of smoking.

The risks of Passive Smoking are computed in Life Ahead using the model for cigarette smoking. Recall that the basic risks of disease and death in Life Ahead are computed for a Non Smoking population. Thus prior to any other computations these risks are estimated via the smoking model using the above values of cigarettes per day, and risk via cigarettes modified as above. The basic values of risk of each disease and death at each age are then modified for this Passive Smoking accordingly.

Life ahead forecasts a loss in Well-Days of 406 days for "Little"; 610 Well-Days for "Average" and 920 Well-Days for "Much" exposure to Passive Smoking. These estimates identify a potential loss of up to 2 to 3 years of useful life. People have a serious reason to avoid being in a smoking environment.

Estimating and Managing the Risk: The risk of Passive Smoking – as for Pollution - is noted in Life Ahead results as a "Non-actionable" health factor. The risk of Passive Smoking accumulates most seriously from exposures of 20 or more years’ duration. In the real world there was not much many could do about it in the past Non-smoking spouses of smoking partners simply were exposed and exposed for the duration of smoking in a marriage. We were exposed in public buildings and in workplaces that in the past did not prohibit smoking. Although this problem has been diminished during the past several years, it will take at least 10-15 years of near complete ‘Non exposure" for the accumulated past risk to dissipate.

When entering your risk of Passive Smoking consider your probable exposure during the past 20 years and your probable exposure in the future as this will determine your long range risk. The risk associated with a Passive Smoking entry will be included in your Well-Days result only as a reminder that this risk– as somewhat similar to a genetic risk – exists. And that this provides some added incentive for the adopting of more healthful health habits. Obviously, you can reduce this risk just by staying away for cigarette smokers as much as possible.