The chances are they will claim that a cigarette smoked in a car exposes passengers to either 23 or 27 times more secondhand smoke than they would get from a whole night in a smoky bar. Both of these statistics are obviously absurd. The "27 times" canard comes from an unpublished, non-peer-reviewed study presented at a conference nine years ago. It was heavily rigged towards getting the "right" result and finally concluded...
The calculated exposure for a five hour automobile trip with the windows closed/ventilation off and with a smoking rate of 2 cigarettes per hour is 25 times higher than the same exposure scenario in a residence.
"Residence" is not quite a "smoky bar" and "windows closed/ventilation off" is not exactly a realistic scenario for a smoker on a five hour car journey, but nevermind. And no, I don't know why 25 got changed to 27, but this is the reference ASH use for the claim.
The "23 times" claim is even more fun, because it involves a rare mea culpa from tobacco control. In a study in the Canadian Medical Association Journal entitled 'Second-hand smoke in cars: How did the “23 times more toxic” myth turn into fact?', MacKenzie and Freeman showed that the "fact" was entirely without scientific evidence and stemmed from a, obscure quote in a local newspaper in 1998 (as I had revealed on this blog two months earlier).
They concluded with the following unheeded recommendation:
We recommend that researchers and organizations stop using the 23 times more toxic factoid because there appears to be no evidence for it in the scientific literature.
I'll be talking about this on BBC Sussex at around 9.40 am.