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Secondhand Smoke

Lately, people have begun to worry about the health risks of secondhand smoke. Some policymakers and activists are even claiming that the government should crack down on secondhand smoke exposure, given what "the science" indicates about such exposure.

Introducing his office's latest report on secondhand smoke, then-U.S. Surgeon General Richard Carmona asserted that "there is no risk-free level of secondhand smoke exposure," that "breathing secondhand smoke for even a short time can damage cells and set the cancer process in motion," and that children exposed to secondhand smoke will "eventually . . . develop cardiovascular disease and cancers over time." Such claims are certainly alarming. But do the studies Carmona references support his claims, and are their findings as sound as he suggests? (A 1972 U.S. surgeon general's report first addressed passive smoking as a possible threat to nonsmokers and called for an anti-smoking movement. The issue was addressed again in surgeon generals' reports in 1979, 1982, and 1984. A 1986 surgeon general's report concluded involuntary smoking caused lung cancer, but it offered only weak epidemiological evidence to support the claim.)

Lung cancer and cardiovascular diseases develop at advancing ages. Estimating the risk of those diseases posed by secondhand smoke requires knowing the sum of momentary secondhand smoke doses that nonsmokers have internalized over their lifetimes. Such lifetime summations of instant doses are obviously impossible, because concentrations of secondhand smoke in the air, individual rates of inhalation, and metabolic transformations vary from moment to moment, year after year, location to location.

In an effort to circumvent this capital obstacle, all secondhand smoke studies have estimated risk using a misleading marker of "lifetime exposure." Yet, instant exposures also vary uncontrollably over time, so lifetime summations of exposure could not be, and were not, measured.

Typically, the studies asked 60-70 year-old self-declared nonsmokers to recall how many cigarettes, cigars or pipes might have been smoked in their presence during their lifetimes, how thick the smoke might have been in the rooms, whether the windows were open, and similar vagaries. Obtained mostly during brief phone interviews, answers were then recorded as precise measures of lifetime individual exposures.

In reality, it is impossible to summarize accurately from momentary and vague recalls, and with an absurd expectation of precision, the total exposure to secondhand smoke over more than a half-century of a person's lifetime. No measure of cumulative lifetime secondhand smoke exposure was ever possible, so the epidemiologic studies estimated risk based not only on an improper marker of exposure, but also on exposure data that are illusory.

Adding confusion, people with lung cancer or cardiovascular disease are prone to amplify their recall of secondhand smoke exposure. Others will fib about being nonsmokers and will contaminate the results. More than two dozen causes of lung cancer are reported in the professional literature, and over 200 for cardiovascular diseases; their likely intrusions have never been credibly measured and controlled in secondhand smoke studies. Thus, the claimed risks are doubly deceptive because of interferences that could not be calculated and corrected.

In addition, results are not consistently reproducible. The majority of studies do not report a statistically significant change in risk from secondhand smoke exposure, some studies show an increase in risk, and - astoundingly - some show a reduction of risk.

Some prominent anti-smokers have been quietly forthcoming on what "the science" does and does not show. Asked to quantify secondhand smoke risks at a 2006 hearing at the UK House of Lords, Oxford epidemiologist Sir Richard Peto - a leader of the secondhand smoke crusade - replied, "I am sorry not to be more helpful; you want numbers and I could give you numbers..., but what does one make of them? ...These hazards cannot be directly measured."

It has been fashionable to ignore the weakness of "the science" on secondhand smoke, perhaps in the belief that claiming "the science is settled" will lead to policies and public attitudes that will reduce the prevalence of smoking. But such a Faustian bargain is an ominous precedent in public health and political ethics. Consider how minimally such policies as smoking bans in bars and restaurants really reduce the prevalence of smoking, and yet how odious and socially unfair such prohibitions are.

By any sensible account, the anachronism of tobacco use should eventually vanish in an advancing civilization. Why must we promote this process under the tyranny of deception? Presumably, we are grown-up people, with a civilized sense of fair play, and dedicated to disciplined and rational discourse. We are fortunate enough to live in a free country that is respectful of individual choices and rights, including the right to honest public policies. Still, while much is voiced about the merits of forceful advocacy, not enough is said about the fundamental requisite of advancing public health with sustainable evidence, rather than by dangerous, wanton conjectures.

A frank discussion is needed to restore straight thinking in the legitimate uses of "the science" of epidemiology - uses that go well beyond secondhand smoke issues. Today, health rights command high priority on many agendas, as they should. It is not admissible to presume that people expect those rights to be served less than truthfully.

Exposure to secondhand smoke is an unpleasant experience for many nonsmokers, and for decades was considered a nuisance. But the idea that it might actually cause disease in nonsmokers has been around only since the 1970s. Recent surveys show more than 80 percent of Americans now believe secondhand smoke is harmful to nonsmokers.

In 1989 the Environmental Protection Agency (EPA) was charged with further evaluating the evidence for health effects of secondhand smoke. In 1992 EPA published its report, "Respiratory Health Effects of Passive Smoking," claiming secondhand smoke is a serious public health problem, that it kills approximately 3,000 nonsmoking Americans each year from lung cancer, and that it is a Group A carcinogen (like benzene, asbestos, and radon). The report has been used by the tobacco-control movement and government agencies, including public health departments, to justify the imposition of thousands of indoor smoking bans in public places.

EPA's 1992 conclusions are not supported by reliable scientific evidence. The report has been largely discredited and, in 1998, was legally vacated by a federal judge. Even so, the EPA report was cited in the surgeon general's 2006 report on secondhand smoke, where then-Surgeon General Richard Carmona made the absurd claim that there is no risk-free level of exposure to secondhand smoke.

For its 1992 report, EPA arbitrarily chose to equate SHS with mainstream (or firsthand) smoke. One of the agency's stated assumptions was that because there is an association between active smoking and lung cancer, there also must be a similar association between secondhand smoke and lung cancer. But the problem posed by secondhand smoke is entirely different from that found with mainstream smoke. A well-recognized toxicological principle states, "The dose makes the poison."

Accordingly, we physicians record direct exposure to cigarette smoke by smokers in the medical record as "pack-years smoked" (packs smoked per day times the number of years smoked). A smoking history of around 10 pack-years alerts the physician to search for cigarette-caused illness. But even those nonsmokers with the greatest exposure to secondhand smoke probably inhale the equivalent of only a small fraction (around 0.03) of one cigarette per day, which is equivalent to smoking around 10 cigarettes per year.

Another major problem is that the epidemiological studies on which the EPA report is based are statistical studies that can show only correlation and cannot prove causation. One statistical method used to compare the rates of a disease in two populations is relative risk (RR). It is the rate of disease found in the exposed population divided by the rate found in the unexposed population. An RR of 1.0 represents zero increased risk. Because confounding and other factors can obscure a weak association, in order even to suggest causation a very strong association must be found, on the order of at least 300 percent to 400 percent. For example, the studies linking direct cigarette smoking with lung cancer found an incidence in smokers of 20 to around 40 times that in nonsmokers, an association of 2000 percent to 4000 percent.

An even greater problem is the agency's lowering of the confidence interval (CI) used in its report. Epidemiologists calculate confidence intervals to express the likelihood a result could happen just by chance. A CI of 95 percent allows a 5 percent possibility that the results occurred only by chance.

Before its 1992 report, EPA had always used epidemiology's gold standard CI of 95 percent to measure statistical significance. But because the U.S. studies chosen for the report were not statistically significant within a 95 percent CI, for the first time in its history EPA changed the rules and used a 90 percent CI, which doubled the chance of being wrong.

This allowed it to report a statistically significant 19 percent increase of lung cancer cases in the nonsmoking spouses of smokers over those cases found in nonsmoking spouses of nonsmokers. Even though an amount far short of what is normally required to demonstrate correlation or causality - the agency concluded this was proof secondhand smoke increased the risk of U.S. nonsmokers developing lung cancer by 19 percent.

In November 1995 after a 20-month study, the Congressional Research Service released a detailed analysis of the EPA report that was highly critical of EPA's methods and conclusions. In 1998, in a devastating 92-page opinion, Federal Judge William Osteen vacated the EPA study, declaring it null and void. He found a culture of arrogance, deception, and cover-up at the agency.

Osteen noted, "First, there is evidence in the record supporting the accusation that EPA 'cherry picked' its data. ... In order to confirm its hypothesis, EPA maintained its standard significance level but lowered the confidence interval to 90 percent. This allowed EPA to confirm its hypothesis by finding a relative risk of 1.19, albeit a very weak association. ... EPA cannot show a statistically significant association between secondhand smoke and lung cancer."

The judge added, "EPA publicly committed to a conclusion before the research had begun; adjusted established procedure and scientific norms to validate its conclusion; and aggressively utilized its authority to disseminate findings to establish a de facto regulatory scheme to influence public opinion."

In 2003 a definitive paper on secondhand smoke and lung cancer mortality was published in the British Medical Journal. It is the largest and most detailed study ever reported. The authors studied more than 35,000 California never-smokers over a 39-year period and found no statistically significant association between exposure to secondhand smoke and lung cancer mortality.

The 1992 EPA report is an example of the use of epidemiology to promote belief in an epidemic instead of to investigate one. It has damaged the credibility of EPA and has tainted the fields of epidemiology and public health. In addition, influential anti-tobacco activists, including prominent academics, have unethically attacked the research of eminent scientists in order to further their ideological and political agendas.

The abuse of scientific integrity and the generation of faulty "scientific" outcomes (through the use of pseudoscience) have led to the deception of the American public on a grand scale and to draconian government overregulation and the squandering of public money.

Millions of dollars have been spent promoting belief in SHS as a killer, and more millions of dollars have been spent by businesses in order to comply with thousands of highly restrictive bans, while personal choice and freedom have been denied to millions of smokers. Finally, and perhaps most tragically, all this has diverted resources away from discovering the true cause(s) of lung cancer in nonsmokers.

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