In an effort to promote a provincial ban on smoking in cars in which children are present, an Ontario legislator has claimed that secondhand smoke exposure causes heart disease among young people.
In a press release issued last month, Sault Ste. Marie MPP David Orazietti - the sponsor of the legislation - stated: "This bill is important because research shows young people are especially susceptible to the harmful effects of second hand smoke and as a result they are more likely to suffer from cancer, heart disease, asthma and a number of other respiratory problems."
The claim in question here is that "young people ... are more likely to suffer from ... heart disease" as a result of exposure to secondhand smoke.
Also last month, the Canadian Cancer Society stated that secondhand smoke exposure among children is related to "childhood leukemia, lymphomas, and brain tumours." This statement was also made in support of legislation to ban smoking in cars with children present.
The Rest of the Story
The rest of the story is that the claim by Mr. Orazietti is false and that by the Canadian Cancer Society is premature - it is not yet conclusively demonstrated by the scientific data.
To be sure, the first problem is far worse. The claim that secondhand smoke exposure causes heart disease among children/young people is simply false. Even among heavy active smokers, heart disease does not generally develop until a person reaches their 40's. It generally takes at least 20 years of exposure before someone who starts smoking during childhood will develop heart disease. We almost never see cases of heart disease among young people that are due to tobacco smoke exposure, even among individuals who are active smokers who started smoking at a very early age. So it is factually inaccurate to state that young people are more likely to suffer from heart disease due to secondhand smoke exposure.
While the second claim is not as bad because there is at least some suggestive evidence to support it, I believe that it is premature and unwarranted because the evidence is not yet sufficient to warrant a causal conclusion. Both the United States Surgeon General and the California Environmental Protection Agency reviewed the issue of the relationship between childhood secondhand smoke exposure and childhood leukemia, lymphoma, and brain tumors. Both concluded that while there is some evidence suggestive of a causal relationship, there is not enough evidence to conclude that a causal relationship exists.
The Surgeon General concluded: "The evidence is suggestive but not sufficient to infer a causal relationship between prenatal and postnatal exposure to secondhand smoke and childhood cancer. ... The evidence is inadequate to infer the presence or absence of a causal relationship between exposure to secondhand smoke during infancy and childhood cancer. The evidence is suggestive but not sufficient to infer a causal relationship between prenatal and postnatal exposure to secondhand smoke and childhood leukemias. The evidence is suggestive but not sufficient to infer a causal relationship between prenatal and postnatal exposure to secondhand smoke and childhood lymphomas. The evidence is suggestive but not sufficient to infer a causal relationship between prenatal and postnatal exposure to secondhand smoke and childhood brain tumors."
In other words, the evidence is not sufficient to conclude that there is a causal relationship between secondhand smoke exposure and childhood cancers, leukemia, lymphoma, or brain tumors.
The California Environmental Protection Agency also concluded that the evidence linking secondhand smoke exposure and childhood leukemia, lymphoma, and brain cancer was suggestive, but not sufficient to conclude that there is a causal relationship. Of note, the report clearly stated that the link between secondhand smoke and childhood leukemia, even if causal, is due to pre-conceptual paternal smoking, not secondhand smoke exposure. Similarly, the report noted that even if causal, the relationship between tobacco smoke exposure and childhood brain tumors may be due to pre-conceptual sperm damage, rather than childhood secondhand smoke exposure.
In the first case, I find the communication to be unethical and irresponsible, because I don't think it is appropriate to make false statements to the public in order to promote public policies.
In the second case, I don't think it is an issue of ethics or responsibility; instead, I think it is more of a strategic mistake. If tobacco control groups are too quick to pull the trigger and communicate to the public that there is a causal relationship between secondhand smoke and a particular disease when there is only suggestive evidence, then it becomes much more difficult for these groups to convince the public that their conclusions are sound. Because their scientific reputations need to be beyond reproach, these groups should not disseminate to the public definitive causal conclusions until there is sufficient evidence to draw such causal conclusions.
Finally, let me address the potential argument that I should not be criticizing either of these groups because while they were wrong or premature with their conclusions about one disease, they were correct with respect to other diseases. For example, it is true that childhood exposure to secondhand smoke increases the risk for asthma and other respiratory problems.
The problem is that this is like the Boy Who Cried Wolf. If an anti-smoking group is wrong about one disease, what reason does the public have to believe that they are right about a different disease? Once you have demonstrated that you are willing to make false statements of scientific fact to support your cause, the public may never believe anything you have to say ever again, even if it is on solid scientific ground.
I don't know why the Canadian anti-smoking groups need to follow the U.S. groups' pattern of exaggerating and misrepresenting the scientific evidence. That's one thing I don't want to see us export to other countries.