Smoking in cars: BMA on firmer ground with revised figures

Earlier this week, Full Fact raised doubts about a claim from the British Medical Association (BMA) that smoking in a car exposed people to a level of toxins 23 times higher than would be found in a smoky bar.

The BMA had claimed in a report and its associated press release that:

"Further studies demonstrate that the concentration of toxins in a smoke-filled vehicle is 23 times greater than that of a smoky bar, even under realistic ventilation conditions."

Yet our analysis found that there seemed to be no evidence in the scientific literature to back this up.

Following our factcheck, the BMA withdrew this statement, and in its place they made the somewhat reduced claim that:

"Further studies demonstrate that the concentration of toxins in a smoke-filled vehicle could be up to 11 times greater than that of a smoky bar."

Along with this claim, the BMA cited a new article in its footnotes to support it.

So is this claim any more accurate than the initial one? 

This article, published in the Nicotine & Tobacco Research Journal, and entitled "An experimental investigation of tobacco smoke pollution in cars", did indeed find that:

"In Condition 1 (motionless car with all windows closed), the average level [of toxins] during cigarette smoking... was over 11 times the level in an Irish pub in which smoking was allowed."

The figure used in this comparison (3800 micrograms/m3) for the level of toxins in a car in which a person is smoking is a direct result of the research and experiments done for this study. The figure used in the comparison for the level of toxins in an Irish pub, meanwhile, is from another study, entitled "How Smoke-free Laws Improve Air Quality: A Global Study of Irish Pubs". This study found that international "Irish pubs" in which smoking was allowed had an average toxin level of 340 micrograms/m3.

It seems therefore, that as the BMA has now claimed, there is evidence in the scientific literature to back up the claim that "the concentration of toxins in a smoke-filled vehicle could be up to 11 times greater than that of a smoky bar".

Full Fact will be getting in touch with those media outlets who reported the "23 times more toxic" claim, to ask them to publish a correction, as the BMA, to its credit, swiftly did.