The BMA (British Medical Association) Board of Science in the UK just kicked up a fuss by suggesting a complete smoking ban in cars. It is worth noting that they themselves say, p. 7, there is no other country in the world which bans smoking in vehicles per se. If they want to launch something so controversial, they had better make very sure they get their facts very straight. A briefing for public release like this one should be backed up, and refer to, a systematic literature study. It isn’t enough to put in a few footnotes. It certainly isn’t enough to take part in perpetuating a chain of copying-and-pasting urban myths like “second-hand smoke is 23 times more dangerous in the car than in the home” which seems to have no valid original source and which has been well debunked.
Ben Goldacre picked up on some howlers in the briefing, based on http://normallydistributed.wordpress.com/2011/11/17/behind-the-smokescreen/,
Still, the BMA does cite four actual peer-reviewed studies on smoking in cars, but as these are indeed overall quite worrying I thought I would put the links here to save others time in googling.
http://journal.nzma.org.nz/journal/119-1244/2294/ is an experimental study from New Zealand which suggests that smoking in cars with a window open produced levels of microparticles comparable to those in bars in which smoking is allowed, and smoking in a car with the windows closed produced levels around ten times as high; in each case the levels dropped back to near zero after a few minutes. http://itcconference.com/ITCWorkshopResources/SFA_Resources/TSI_Sidepak_Particle_Monitoring_Refs/Rees–Car_Smoke.pdf is a rather more thorough article which reports levels of microparticles after one cigarette in a car comparable to those in bars (actually, this is the report on which the article is based, as the article itself is subscription-only, yuk). There is a third similar article http://www.ontla.on.ca/library/repository/monoth/11000/280559.pdf which produced dangerous levels closer to those in the NZ study. The fourth relevant study is on airflow and is most worrying because it goes into the medium-term effects; how long do the negative effects linger: http://exposurescience.org/pub/reprints/Ott_etal_Air_Change_Rates_Motor_Vehicles.pdf