Wednesday 16 November 2011

The British Medical Association spices up an old myth with a new lie

I predicted last night that...

The chances are [the British Medical Association] 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.

In the end they plumped for the "23 times" figure despite it being thoroughly debunked in the Canadian Medical Association Journal, which offered this advice to advocates:

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.

Did that stop the BMA resurrecting this zombie statistic?

It did not. Not only are the BMA bandying around a figure for which there is "no evidence in the scientific literature", but they have added a fresh layer of nonsense to it.

There is evidence to suggest that the levels of SHS present in vehicles can contribute to a serious health hazard for adults and children.

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.

In the studies a number of ventilation conditions were assessed, where airflow parameters included average driving speed, presence of air conditioning and open windows. Realistic ventilation is described as driving at average roads speeds with all four windows completely open.

The BMA seem to be suffering from undiagnosed pseudologia fantastica. Their new briefing paper supplies three references for their bizarre claim about "realistic ventilation". Only one of the named studies experimented with a scenario in which all the windows were open. The researchers called it 'Condition 3' (PM is particulate matter)...

At the other extreme, in Condition 3 (all windows open all the way while driving), the PM2.5 level was the lowest (M = 60.4 μg/m3, range = 15.7 to 220.5 μg/m3).

And how does that compare to a "smoky pub"?

To provide some context about the PM2.5 levels recorded in this study, in a recent report of PM2.5 levels in Irish pubs throughout the world, the average level of PM2.5 in 48 Irish pubs that allowed smoking was 340 μg/m3.

Pedants and sceptics would say that there is a bit of a difference between "23 times higher" and "82% lower" but what the hell, eh? If the BMA says it, it must be true.


Xopher said...


"Up to one million hospital patients affected by medical negligence

The Public Accounts Committee (PAC) has revealed that medical negligence affects one in ten patients staying in UK hospitals.

It is estimated that nearly a million people have suffered unnecessarily as a result of medical blunders made by doctors, nurses, and other medical professionals. It is not known exactly how many patients were involved in fatal accidents, but they are thought to number over 2,000.

These blunders consisted of a range of incidents, including misdiagnoses, surgical errors, the administering of wrong doses of medication and falls."

The BMA represents people who fail to do the jobs they are qualified for but consider themselves sufficiently expert to interfere in areas they have no qualifications.

Blogger said...

When they say 'smoky pub' I think they must mean a normal modern UK pub...

i.e. one with no smoking inside but the occasional waft in from the door or garden.

A car could well be smokier than that!

SteveW said...

Predictable enough, the BBC are in receipt of yet another of my complaints.

Can't email you details Chris, just moved house and my internet is temperamental to say the least - should be sorted in 9 days (apparently)

JJ said...

Chris where did you get the 27 times more toxic from, did this come from the Rocky Mountain News rag, in Denver Colorado? I've tried in vain to find any reference to it.

JJ said...

Any chance of a reply?

Christopher Snowdon said...

The roots of the 27 times are discussed in this post. It is distinct from the 23 times myth: