Intended for healthcare professionals

Rapid response to:

Paper
# Environmental tobacco smoke and tobacco related mortality in a prospective study of Californians, 1960-98

BMJ
2003;
326
doi: https://doi.org/10.1136/bmj.326.7398.1057
(Published 15 May 2003)
Cite this as: BMJ 2003;326:1057

## Rapid Response:

## Re: Professor Repace has gone quiet

I must admit that, although I regard myself as reasonably

intelligent, I cannot be very clever because most of the statistical stuff

above is beyond me. I mean, I understand that if there are 10 horses in a

race, the probability is 9:1 that one of them will win the race. However,

it is fairly common for 'dead heats' to occur where 2 horses cross the

finishing line so closely together that no difference in position can be

seen. I would suppose that, if one found in reality that the occurrence of

'dead heats' was, say, 1 in 1000, the probability of a 9:1 ratio would

have to be reduced a little. I am not quite sure of my maths, but perhaps

8.999:1 would be correct? But one might go on to ask what is the

probability of a three way dead heat? It must happen occasionally - or

must it? Even if it has never happened in the past, it is still possible,

isn't it? In fact, it is always possible that all 10 horses could be

involved in a 'dead heat'.

As regards Passive Smoking, the statistical problem that arises in my

mind (and I very much stand to be corrected) is this. If we take the

probability of a smoker to be significantly affected by smoking to be

100%, do we see the probability of a passive smoker to be, say, 1%? Or

should that probability be 0.1%? Or even, 0.01%? Or even 0.001%?

Further, in the same way that it is always possible that 10 horses in

a race could possibly cross the finishing line at the same time, is it

right to project a minuscule possible percentage probability by virtue of

some sort of population multiplier to project an actual number of deaths

based on minuscule probabilities?

I must admit that Mr Atherton's sources bother me a little. If it is

true that the sources he quotes are funded by the tobacco industry, then

they may be suspect. But I did not see in Atherton's submission anything

self-contradictory.

In Repace's submission however, I did see a logical inconsistency.

Now, because I am afraid of what I might do to this response if I try

to go back, I will have to try to remember. Did Repace say that the the

incidence of harmful chemicals from tobacco smoke INSIDE enclosed premises

is 2 or 3 orders of magnitudes greater than the incidence OUTSIDE enclosed

premises? Words to that effect.

If we reasonably assume that, in most circumstances, the harmful

incidence (if I may reverse the logic a little) of tobacco smoke OUTSIDE

enclosed premises is unutterably minuscule for all intents and purposes

(bearing in mind the minuscule amount of carcinogenic chemicals in tobacco

smoke anyway), then '2 or 3 orders of magnitude' is still virtually zero.

It follows, therefore, that in Repace's opinion, the incidence of harmful

chemicals resulting from tobacco smoke INSIDE enclosed premises (in

normal, everyday circumstances) is zero, for all intents and purposes

(that is, as regards damage to health).

Repace is a very clever Professor. I am not.

Competing interests:

None declared

Competing interests:No competing interests24 February 2010