Second-hand smoke
There was an interesting story on digg about a new law in a US state that would make it illegal to smoke in a car with young children present.
While there are numerous arguments as to why this might not be good public policy, the one that was most often raised was that the negative health effects of second-hand smoke were doubtful. I don’t know why I argue with such troll-worthy commentators, but for what it’s worth, my response is posted below. (Yeah, I was really bored… heeh…)
A number of commentators to this article have brought up some variation on the argument that the harmful effects of second hand smoking have not been ‘proven’. Many refer to the 2003 BMJ study by Enstrom and Kabat, which looked at the spouses of adult smokers compared to non-smokers and their rate of death from heart disease, lung cancer, and COPD (medical conditions commonly associated with smoking, and second-hand smoke). The study claimed that there was no difference in the rates of these diseases in studied participants. Link
First off, that study has little to no relevance to this particular article (banning smoking in a car with young children present). Even if the BMJ study were rock-solid, all it would prove is that second-hand smoke is not harmful to adults. One can only make a very tenuous hypothesis that this would also apply to children. For example, doses of many drugs that are safe for adults would be toxic for a young child.
Furthermore, the study by Enstrom has a number of fatal flaws, most notable of which is an inability to differentiate people who were exposed to second-hand smoke from those who were not. Link.
In addition, there are numerous, scientifically rigorous studies detailing correlation between second hand smoke and adverse health outcomes, one of which is mentioned in the article above, or do a search on PubMed which brings up thousands of results, mostly supporting harm from smoking. See also the report on carcinogens.
I also came across an interesting study that compared papers showing negative effects from second-hand smoke to those which showed no effects. The biggest difference? The papers which showed no effect were 88 times more likely to be funded by tobacco companies. Link.
Furthermore, in specific relation to children, there are numerous studies once again detailing a high correlation between smoking and adverse health outcomes such as Sudden Infant Death Syndrome (see Anderson and Cook, Thorax Vol 52 No 11, Nov 1997 pp 1003-1009.), respiratory illness, middle ear disease, lung function, and exacerbation of asthma. (see a great comprehensive review, Hofhuis et al. Arch Dis Child 2003;88:1086-1090.)
Strictly speaking, the naysayers are right, this is not “proof” that second-hand smoking causes harm (in theory it could be cause by something else we are overlooking). We are all told that correlation does not equal causation (witness the meme regarding pirates and global warming). However, if there is a plausible biologic mechanism, as in this case, correlation is strongly suggestive of causation. To obtain the gold-standard of scientific proof, one would need to do a randomized control trial and essentially blow smoke in babies faces and see if they do worse than non-exposed babies. Try to run THAT design by your local ethics committee. (Especially since similar studies in animals have indeed shown harm).
To ignore the enormous amount of evidence is to be the proverbial ostrich sticking your head in the sand; cigarette smoke clearly does cause harm; the question is how much, and to find the best way of limiting that harm to others, especially children.
Other references:
http://www.ccohs.ca/oshanswers/psychosocial/ets_health.html
http://www.smoke-free.ca/Second-Hand-Smoke/health_kids.htm
http://www.cbc.ca/story/news/national/2003/05/16/smoking030516.html
Schick and Glantz, Philip Morris toxicological experiments with fresh sidestream smoke: more toxic than mainstream smoke, Tobacco Control 2005; 14:396-404.
Brims and Chauhan. Air Quality, Tobacco Smoke, Urban Crowding and Day Care; Modern Menaces and Their Effects on Health. Pediatric Infectious Disease Journal. 2005 International Congress on Respiratory Viruses. 24(11) Supplement S152-158, November 2005.
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