Right. Now PAH concentrations are the thing. PAHs are polycyclic aromatic hydrocarbons. PAHs are carcinogenic, and a subdivision of PAHs, BaPs, are particularly so. BaPs are benzo(a)pyrenes. Local councils monitor average levels of PAHs in the air in
The average level of PAHs in the air in Westminster in the orange PM10 areas are currently around 35 ng/m3. This is what you and your kids will be breathing in a car on these roads. Constantly. All the time. With every breath.
Now cigarettes produce both smoke particles and PAHs. So how much worse off will you be with a smoker in the car? A report from the University of Minnesota Cancer centre says;
The presence of BaP and other carcinogenic PAHs in cigarette smoke is firmly established. Current levels of BaP are 1.5–15 ng per cigarette, whereas those of other established PAH carcinogens are collectively ≈3–50 ng per cigaretteNow of course the smoker inhales and absorbs a large proportion of that - let's say half. The volume of a car passenger compartment is about 3m3. So if a smoker in the car smoked an entire cigarette instantaneously, with no venting of the smoke and all of the smoke and vapour phase hanging in the air, it would result in a PAH level of 0.5 - 8 ng/m3 or about a maximum of about a quarter of the ambient level. With a window cranked open a fraction, and normal time taken to smoke a cigarette, the increase in PAH levels in the atmosphere inside the car is practically zero.
So go figure why the smoking Nazis (in this case the Lung Foundation and the RCP) are calling for a ban on smoking in cars.