According to a statement by Smokefree Air for Everyone (Columbia, MO) published in the Columbia Business Times, being exposed to secondhand smoke for just 20 minutes puts you at risk of having a stroke due to the formation of blood clots:
"After 20 minutes, blood platelets look like a pack-a-day smoker’s, making your blood “sticky” and contributing to stroke causing blood clots."
The Rest of the Story
I consider this statement to be inaccurate, and I think it might unnecessarily scare people into thinking that if they are exposed to secondhand smoke for just 20 minutes, they might develop a blood clot and suffer a stroke.
The good news is that the statement is not accurate. If you are an otherwise healthy person -- or in fact, even if you are unhealthy but as long as you do not have severe pre-existing cerebrovascular disease (atherosclerosis of the arteries supplying the brain), you are not at risk of suffering a stroke from 20 minutes of secondhand smoke exposure.
While it is true that chronic exposure to secondhand smoke can cause atherosclerosis and put an individual at increased risk of a stroke, a mere 20 minutes of exposure cannot cause a stroke in anyone who does not already have severe cerebrovascular disease and who is already basically a stroke waiting to happen.
In other words, if someone has cerebrovascular disease that is so severe that any temporary increase in platelet activation may be enough to trigger life-threatening clot formation, then that individual is at severe risk of suffering a stroke, from secondhand smoke exposure, eating a high-fat meal (which can also activate platelets), or any of a large number of other exposures.
The important point here is that the claim is not qualified as applying only to people with extremely severe, pre-existing cerebrovascular disease. The way I read the statement, it is applying to anyone. After all, it states that 20 minutes of secondhand smoke makes "your" blood sticky, putting you at increased risk of a stroke. Thus, it seems intended to apply to any reader, meaning that it is a general statement of increased risk for the entire exposed public.
While I agree wholeheartedly with the goals of the SAFE coalition and support the Columbia smoke-free workplace law, I am uncomfortable with the idea of using exaggerated, misleading, and fallacious health claims in order to support those goals and that law.
I think the actual effects of secondhand smoke are enough; we do not need to go beyond the truth in order to promote our policy goals.