Letter Informing Anti-Smoking Groups of Their Misleading Claims About Secondhand Smoke Widely Disseminated; Now It's Time for Action

I sent the following letter to my private secondhand smoke mailing list, consisting of a large number of anti-smoking groups involved in the secondhand smoke issue, many of which are making misleading and/or inaccurate claims about the health effects of secondhand smoke. Now we'll see what these groups are really made of. Will they correct their fact sheets to reflect the science, or will they intentionally retain their misleading claims to deceive the public?

The Rest of the Story will report early next week on whether any changes were made on the web sites of the organizations who received this letter.

To me, this is an important moment in the tobacco control movement. While I have been reluctant to, and have not yet, accused anti-smoking groups of intentionally misleading the public, failure to correct their communications knowing that they are wrong would constitute an intentional deception of the public. The response of anti-smoking groups to this letter will go a long way towards indicating the direction that the movement is headed.

Will we pride ourselves on our scientific integrity, or will we put the ends above the means and use unethical tactics to promote our agenda?

The Rest of the Story (The Letter)

There seems to be a great deal of confusion about some of the health effects of secondhand smoke, especially the acute cardiovascular effects of secondhand smoke, which is leading to a number of anti-smoking groups publicly making claims about the health risks of secondhand smoke that I'm afraid are misleading, and in some cases, inaccurate. The purpose of this note is to try to clarify some of this confusion. I realize that the scientific studies are very difficult to read and understand, so I'll try to explain the science as best I can.

First of all, to give you an idea of the kinds of misleading claims that are being made:

EXAMPLE 1: The August 30 press release of one anti-smoking group claimed: "Research studies have shown that even just thirty seconds of exposure to secondhand smoke can make coronary artery function of non-smokers indistinguishable from smokers." (see here for details)

This type of message is a problem, not only because it is inaccurate, but because it undermines the public's appreciation of the severe cardiovascular effects of smoking. If people really believe the statement, and therefore believe that chronic active smoking is no worse than a mere 30 seconds of exposure to secondhand smoke in terms of coronary artery function, then what reason is there for people to quit smoking? Obviously, people who are exposed to secondhand smoke for 30 seconds do not have the same damage to their coronary arteries as people who smoke actively for years. Even if this was just a mistake and it meant to say 30 minutes, it is still untrue that the damage to coronary artery function due to 30 minutes of secondhand smoke exposure is the same as the damage done by years of active smoking. I explain this fallacy in some detail below.

EXAMPLE 2: One major anti-smoking organization claims that: "Even a half hour of secondhand smoke exposure causes heart damage similar to that of habitual smokers. Nonsmokers' heart arteries showed a reduced ability to dilate, diminishing the ability of the heart to get life-giving blood." (see here for details)

This type of message is very dangerous - first, because it is fallacious; and second, because it undermines the risks of active smoking. It claims that the heart damage suffered by long-time smokers is no worse than that suffered by a nonsmoker exposed for just 30 minutes, which is completely ridiculous, but if believed, would suggest to a smoker that his or her smoking really wasn't all that bad.

EXAMPLE 3: A smoking ban manual put out by another anti-smoking group claims that: "Current scientific data suggest that eating in a smoky restaurant can precipitate myocardial infarctions in nonsmokers and increase the risk of fatal and non-fatal cardiac events in nonsmokers by about 30 percent." (see here for details)

By suggesting that eating out in a smoky restaurant increases the risk of heart disease by 30%, this message is not only inaccurate, but it also undermines the public's appreciation of the risks of smoking. If the risk of developing heart disease from active smoking is only as high as the risk a nonsmoker faces from eating out 4 times at a smoky restaurant (which this claim implies), then isn't a person better off actively smoking then being a nonsmoker and going out occasionally to a restaurant that allows smoking?

EXAMPLE 4: A large number of anti-smoking groups are claiming that secondhand smoke exposure causes pulmonary emphysema. For example, one group states that: "Secondhand smoke can cause the debilitating disease pulmonary emphysema, causing severe damage to the walls of the air sacs, with the lungs losing their capacity to expand and contract." (see here as well as here for details)

Unfortunately, there is simply not evidence to support such a claim at this time. Neither the incredibly comprehensive California EPA report nor the Surgeon General's report concluded that secondhand smoke causes emphysema. The Surgeon General's report actually concluded that the evidence is NOT sufficient to support a claim that secondhand smoke causes emphysema, and the California EPA report doesn't draw any such conclusion.

EXAMPLE 5: Many groups are claiming that 30 minutes of secondhand smoke exposure can cause atherosclerosis (hardening of the arteries), heart disease, or fatal or catastrophic arrhythmias, or that it can cause a heart attack in an otherwise healthy person. For example, one group claimed that: "Only 30 minutes of secondhand smoke exposure can cause narrowing of blood vessels, restricting the flow of blood and contributing to hardening of the arteries" and that "After 120 minutes of exposure, your heart rate variability is reduced, increasing the chance of an irregular heart beat that can itself be fatal or trigger a heart attack." (see here for details)

BRIEF SECONDHAND SMOKE EXPOSURE AND HEART DISEASE

The first thing that groups need to understand is that brief secondhand smoke exposure (such as 30 minutes, 2 hours, etc.) does not cause atherosclerosis, hardening of the arteries, or heart disease. These processes take many years to develop. Even among heavy smokers, we don't see evidence of any of these things until they reach at least 40 years old. In other words, it takes at least 20 years for the process of atherosclerosis to occur and for heart disease to develop. So 30 minutes of exposure does not cause narrowing of blood vessels. Such narrowing takes many years to happen.

So why are these "30 minute" claims being made? The confusion stems from a study that was published in JAMA in 2001 by Otsuka et al. These researchers found that 30 minutes of secondhand smoke exposure resulted in a decrease in something called coronary reserve flow velocity. This is a measure of the ability of the coronary arteries' ability to dilate under artifically induced conditions. A decrease in coronary reserve flow velocity indicates an impairment of the ability of the arteries to dilate, which indicates that endothelial dysfunction is taking place. Endothelial cells are the cells that line the inside of the coronary arteries. When they don't function properly, then the artery is not able to dilate normally in response to certain artifically induced stresses, and thus the measured reserve flow velocity is decreased.

However, it is important to realize that there is no clinical significance of the decrease in reserve flow velocity in terms of that single secondhand smoke exposure. The endothelial dysfunction is reversible, and if the person is not exposed again to secondhand smoke, there is no risk that the brief exposure will result in atherosclerosis. What the Otsuka study demonstrates is that if someone had chronic exposure to secondhand smoke, there is a plausible biologic mechanism by which that exposure could lead to atherosclerosis: namely, that continued endothelial dysfunction occurs. And endothelial dysfunction is an early precursor to atherosclerosis.

It is also critical to realize that a decrease in coronary reserve flow velocity does NOT mean that coronary blood flow is reduced in the individual. In fact, Otsuka et al. found that the basal coronary blood flow was unaffected by 30 minutes of exposure to secondhand smoke. Thus, the 30-minute exposure does not cause "heart damage," or diminish "the ability of the heart to get life-giving blood," as one anti-smoking group publicly claims.

In summary, then, there is no evidence that a 30 minute exposure to secondhand smoke can cause atherosclerosis, hardening of the arteries, narrowed arteries, or heart disease. In fact, it's biologically impossible for this to be the case, since it takes years and years for these processes to occur.

You should be aware that eating a hamburger also causes endothelial dysfunction and decreases coronary reserve flow velocity. But it wouldn't be accurate to claim that eating a hamburger causes narrowing of the coronary arteries, makes it harder for the heart to get life-giving blood, or triggers a heart attack.

BRIEF SECONDHAND SMOKE EXPOSURE AND FATAL ARRHYTHMIAS

Although a number of anti-smoking groups are claiming that just 2 hours of exposure to secondhand smoke can cause fatal or catastrophic cardiac arrhythmias, this is not the case - there is no evidence for this at all.

So why are these "2 hour" claims being made? The confusion stems from a study that was published in 2001 by Pope et al. The study found that after 2 hours of heavy secondhand smoke exposure, nonsmokers experienced something called decreased heart rate variability. There is some evidence that in people with severe heart disease, decreased heart rate variability may predispose to catastrophic arrthymias. However, in a healthy person, the observed effects of 2 hours of secondhand smoke exposure on heart rate variability are of no clinical significance. Like the Otsuka study, the importance of this study is that it demonstrates yet another plausible biologic mechanism by which chronic secondhand smoke exposure can cause heart disease. But it is absolutely false to claim that a 2 hour exposure to secondhand smoke causes fatal or catastrophic cardiac arrhythmias.

BRIEF SECONDHAND SMOKE EXPOSURE AND HEART ATTACKS

Although a very large number of anti-smoking groups are claiming that 30 minutes of secondhand smoke exposure can cause heart attacks in otherwise healthy people (they are not qualifying this claim by making it clear that it relates only to people with severe pre-existing coronary artery disease), this is also a false claim. There is simply no way (and no evidence) that a 30 minute exposure can induce a heart attack in a person who doesn't have severe coronary artery stenosis (narrowing) to begin with.

It is at least possible that if someone has severe coronary artery stenosis, a brief secondhand smoke exposure could be the final trigger that causes a heart attack, although there is really no evidence that this occurs in practice. If groups want to make such a claim, I don't think it is necessarily problematic, but it should be made very clear that the claim is only referring to people who already have severe heart disease. I myself wouldn't make such a claim because I don't think there is any evidence to support it in practice; however, it is at least a theoretical possibility, unlike any of the other above claims.

SECONDHAND SMOKE EXPOSURE AND EMPHYSEMA

Although many anti-smoking groups are claiming that secondhand smoke exposure causes pulmonary emphysema, the California EPA (which has been quite aggressive in its implication of secondhand smoke in various diseases - it concluded that secondhand smoke causes breast cancer above the objections of the American Cancer Society) did not even suggest that secondhand smoke causes emphysema. The Surgeon General's report concluded that there is not adequate evidence to make such a claim.

Perhaps my most detailed attempt to clarify these issues can be found here.

Why is this all so important?

First, because I think we have a responsibility to the public to be accurate in our scientific claims. We constantly criticize the tobacco companies for misleading the public with their health claims. To retain credibility and avoid hypocrisy, we should not be misleading the public with our own fallacious health claims.

Second, because we risk losing our credibility and therefore our effectiveness in promoting smoking bans if we are recognized as being untrustworthy in our public communications. The tobacco companies are avidly making note of all of the above misleading claims. These misleading claims are receiving public attention.

For example, just this past Friday, Jacob Sullum highlighted the 30-second claim on Reason Online's Hit&Run blog. A recent JAMA article highlighted some of these misleading claims. An op-ed I published in the St. Paul Pioneer Press also brought these issues to light.

I think we've got tremendous momentum in our efforts to protect the public from the hazards of secondhand smoke. And we've got the truth on our side. I think the truth is enough. I don't think we need to misrepresent the scientific evidence and exaggerate or sensationalize the health effects to make our point.

Ultimately, I think that by risking the credibility as well as scientific integrity of the entire smoke-free movement, we have a lot more to lose than any transient gains we may obtain by using these misleading claims to create more dramatic sound bites for the media and the public.