PUTTING SOME PERSPECTIVE INTO THE DEBATE ON HEALTH RISKS OF TOBACCO SMOKE


Unless you've investigated the facts for yourself, you probably think that smoking is the quick road to an early death. Well, read on.....

Whenever you read about the risks of smoking, the risks are almost always referred to as relative risks such as "increased"risk, "higher risk", 50% higher risk, 10 times the risk, etc., and rarely as "absolute risks". The increased risk usually means an increased risk compared to someone who never smokes (but you need to look carefully at the definition to be clear). By absolute risks it means a statement which tells us, say, out of 100,000 smokers how many will die this year, or over the next five years, etc.? (and of course, the information is complicated by factors about intensity of smoking, age, sex, lifestyle etc).

Relative risk doesn't really help you take an informed decision about smoking - information on absolute risk is much more useful.

Why is relative risk used more than absolute risk? - because it is easier to sensationalise relative risk, and sensationalism sells newspapers, sells research projects, brings in more funding for further research and generally makes it easier to manipulate and inflame public opinion.

DIRECT SMOKING RISKS

However, here is one graph showing absolute risks which helps put risks into perspective. Cigarette smoking is generally considered to be more risky than cigar smoking, although cigars can cause similar hazards if their smoke is inhaled. Cigarettes, cigar and pipe smoking cause comparable hazards for cancers of the oral cavity, pharynx, extrinsic larynx and oesophagus.


Cigar lung cancer rates compared with cigarettes


The graph above comes from a wide review of cigar smoking reported in 1998 by the National Cancer Institute (US). It compared all available data on the health risks associated with cigar smoking with risks associated with cigarette smoking.

The graph relates to lung cancer specifically, and compares lung cancer death rates of cigarette and cigar smokers for various levels of cigar smoking and inhalation of the smoke.

The upper solid line denotes a 20 cigarette a day smoker's annual death rate assuming commencement at age 18. In the smoker's 60th year there are approx. 200 smoker deaths per 100,000 (or 2 per 1,000), whereas neversmokers have a lung cancer death rate of around 13 per 100,000 at this age.

Hence the 20 a day smokers have an increased risk of around 16 times those of never smokers. This would normally be reported in the press as "20-a-day- smokers at age 60 have nearly 20 times risk of dying from lung cancer than non-smokers", which sounds a lot more frightening than the absolute figures (2 per 1000) at age 60 - even after 42 years of smoking 20 cigarettes a day.

As age increases so does the risk. If the smoker reaches his 85th year (!) the risk for the 20-a-day cigarette smoker is around 1100 per 100,000 (11 per 1000), with non-smokers risks rising to around 90 per 100,000 (0.9 per 1000).

However, as these figures are annually cumulative the end result gives an overall number of smoker deaths by age 85 of around 16,000 per 100,000, or 16 per 100 - an ultimate death rate from lung cancer of less than 1 in 5 after spending nearly 70 years smoking their way through around half a million cigarettes.

Also, looked at another way, 84 per 100 smokers will not die of lung cancer by their 85th year, even after smoking 20 cigarettes a day for 67 years.

Not such an instant death sentence then.......

(Bear in mind that these figures are for lung cancer only, and when the other smoking risks are added they will increase the overall risk of death for a smoker.)

Also, of course, most people will have died of something by age 85.

It should also be pointed out that by adopting various lifestyle behaviours such as: reducing the number of cigarettes smoked; not inhaling so deeply; undertaking regular (moderately intense) exercise; eating a diet rich in fruit and vegetables; and only drinking modest amounts of alcohol can substantially reduce the risks associated with smoking.




PASSIVE SMOKING ABSOLUTE RISKS

The current consensus of the anti-smoking lobby is that the increased risk of getting lung cancer for non-smokers living with smokers is around 20% - 30%, which sounds like something you might want to work hard to avoid until you see (below) the absolute risk.

Even assuming for the moment that this supposed increased risk from second hand smoke is actually valid, the absolute risks are very small as shown below.

The red line on the graph represents the supposed increased lung cancer risk of between 20%-30% for non-smoking wives married to smoking husbands,

It should also be made clear, and often it is not, that this figure is derived from data relating to non-smoking wives living with a smoker, i.e. fairly continuous and relatively intense exposure compared with neversmokers.. Thus, the intensity of exposure will be relatively high, since it will occur not only in the home, but also in all social activities which they would tend to be involved in together, and with like minded smoking friends/family.

Also, the data relate to the time when exposure to second hand smoke was high in both the workplace and the leisure industry, and not like the period in the early 2000s just prior to the ban when "Non-Smoking areas" were prevalent and smoking in the workplace was generally a thing of the past.

From the graph, neversmokers in their 60th year have deaths of around 13 per 100,000. So, the non-smoking wives have an increased risk (20%-30%) of between 0.026 per 1000 and 0.039 per 1000. That is, a max increased risk of around 4 per 100,000.

During the period just prior to the ban, the exposure of the general non-smoking public to second hand smoke will have been very low, probably around 1% or less of the relatively intense exposure of the non-smoking wives to which the 20% - 30% increased risk relates.

Assuming that there is no cut-off point for exposure to second hand smoke below which it has no effect (disputed and probably wrong), then this brings the effective increase in risk of 20%-30% down to around 0.2% to 0.3%. for neversmokers.

So the maximum increased risk for a neversmoker dying of cancer in their 60th year due to second hand smoke exposure will be around 13 x 0.003 = 0.039 per 100,000, or 3.9 per 10 million, or substantially less than 1 in a million.

Hence, neversmokers not married to smokers were clearly at such a low level of risk that it was, for all practical purposes, entirely negligible.

Consequently, as a measure to protect the health of neversmokers, the ban was entirely unnecessary.

The position of non-smoking employees is slightly different, in that they may have to work in smoking areas. So, non-smoking employees working in smoking areas may have a similar risk increase to the non-smoking wives married to smoking husbands, i.e. max increased risk of 4 per 100,000.

Imposing proper ventilation and other more specific measures, such as air curtains to shield the main working area from smoke, would be able to bring this risk down by at least a quarter, to 1 per 100,000 or with good design down by a factor of ten. So, employees could have been readily protected from the (still supposed) risks from second hand smoke.

The above evaluation is based on the assumption that the 20% - 30% increased risk associated with ETS is valid. This is disputed and probably wrong if one considers the well known bias in reporting positive research results compared with the reporting of null or negative results, particularly under the pressure applied by the anti-smoking lobby to scientists who give any support to the "no measureable effect" hypothesis.

Yet it was with these data that the anti-smoking lobby convinced the government to impose the draconian ban in July 2007 which has caused so much anger, distress and loss of livelihood.


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** Page last updated April 2010 **