In considering the impact of second hand smoke on non-smokers, a number of important factors have conveniently been ignored.
In summary they cover :-
The effect known as hormesis, whereby many toxic compounds (even dioxin) appear to be beneficial at low concentrations;
Smoke from cooking fires and burning vegetation has been man's constant companion for over 250,000 years - some tolerance and immunity to low exposure will undoubtedly have developed;
Recent research has shown that the negative effect of smoking on the smoker's health (for middle aged people) appears to be balanced by each of 3 other healthy behaviours, eating a diet rich in fruit/veg, undertaking moderate exercise, and drinking alcohol only moderately.
This implies that actual smoking is only as harmful as drinking heavily, or not eating a diet high in fruit and veg, or not regularly exercising. Not the imminent death sentence it is portrayed as?
Relative risks are used to readily alarm the non-technical public - absolute risks put the dangers of smoking itself into perspective -
Did you know that smokers who have smoked 20 cigarettes a day since the age of 18, will, in their 60th year, have a death rate from lung cancer of 2 per 1000? (see detail in (4.) below.)
So what practical effect will an occasional whiff of second hand smoke have?
There is substantial uncertainty in the accuracy of the data sets used in the SHS debate due to :-
a) incomplete information/knowledge on the varying factors involved in lung cancer;
b) much information about past smoking behaviour and contact with smoke is based on self-reporting and recollections, known to be unreliable;
c) bias introduced into research data sets by scientists failing to publish results which do not have a positive result.
As the SHS correlations with lung cancer risk are so low, it would take only a very small change in accuracy of reporting to, in the case of SHS, push the result towards a lower or even negative correlation for the risk of contracting lung cancer.
Together these issues introduce considerable uncertainty into the overall data sets which would normally require a more stringent quality standard for accepting correlation rather than the reduced one used in the SHS debate.
In more detail :-
A number of the epidemiology studies (including the infamous WHO 1998 Report Study) which showed a protective effect associated with second hand smoke were ignored by the anti-smoking lobby based on their assumption that these couldn't possibly be right, hence the study must have been faulty.
However, there is a plausible reason for a beneficial effect and the name of the phenomenon is Hormesis, where many toxic chemicals (including even dioxin) show a beneficial effect on health at low concentrations.(see: Deadly Poisons Reveal their Friendly Side) This has been viewed with skepticism by a number of scientists, but the authors have recently firmed up on their hypothesis.
The reason for this is unclear, but one hypothesis put forward suggests that at low concentrations the body's repair mechanisms are stimulated to repair the damage, and once having been stimulated may mop up other damage in the process
If correct, this implies, quite plausibly, and in a similar way to dirt/germs in early childhood helping to protect against asthma onset, that low concentrations of tobacco smoke may actually provide some protection against lung cancer.
It is clear that more research needs to be carried out into this phenomenon.
Fire for Cooking
Given that man discovered fire for cooking at least a quarter of a million years ago (some say it might even be a million years ago), then it seems self evident that man has evolved in close daily contact with burning vegetation, and will undoubtedly have developed some level of tolerance and immunity from the effects of such smoke.
Four relatively simple, healthy behaviours
Apparently, for middle aged and older people:-
"The millions of people resolving to live a healthier life in 2008 can take heart. Four relatively simple healthy behaviours, may add 14 years to your life, say researchers. Even better, they help no matter how fat or unhealthy you are already". It was in the reduction of deaths attributed to cardiovascular disease where the findings were most pronounced, with those scoring zero five times more likely to succumb than those scoring four. But there was also a relationship between score and cancer deaths.
While the main analysis excluded people with known disease, the researchers found that those with serious conditions fared better the higher they scored than those who scored lower. The full research paper is shown here.
The study covered 20,000 people in the Norfolk county of England over
the period 1993-2006, ages ranging from 45 to 79 not, as far as they were aware at the time, having cancer or any heart problems.
A point was awarded for each of the following:
1. not currently smoking;
2. consuming between one and 14 units of alcohol per week (one unit of alcohol is approx. equivalent to half a pint of beer or one small glass of wine);
3. eating five servings of fruit/vegetables each day;
4. not being inactive.
This last category was defined as either having a sedentary (sit down most of day) occupation and taking half an hour of exercise a day, or simply having a non-sedentary job like a nurse or plumber. (The exercise criteria were based on reported hours of exercise per week, and the total divided by 7 to get an average daily amount.)
The message seems clear - and quite welcome! If you currently smoke, you can only get a maximum of 3 points if you do the others, i.e. exercise, eat a diet with lots of fruit and vegetables, and drink moderately. On the graph this implies that out of a 100 people who scored 3 points 92 are likely be alive after 14 years and 8 are likely to be dead.
If you don't smoke and also meet the other 3 requirements, you get the maximum of 4 points. This means that out of every 100 people scoring 4 points, 95 are likely to be alive after 14 years and 5 are likely to be dead.
If you scored zero points, then out of the 100, 75 are likely to be alive with 25 being dead within 14 years.
The other interesting point is that if you smoke, exercise and drink only moderately (but don't eat plenty of fruit and vegetables), you would be better off than someone who doesn't smoke but neither exercises, drinks, or eats the required fruit and vegetables.
An interactive version of this research is available at a University of Cambridge site called Understanding Uncertainty. (Requires Flash Player).
The implications are that smoking as a risk in the relatively short term (14 years) is similar to the risks of not exercising, or not drinking at all, or drinking to excess, or rarely eating fruit and vegetables.
The message is simple - if you don't want to give up smoking, then modify your lifestyle to include doing points 2, 3, and 4 as specified. If you are a regular pub drinker, then 7 pints of beer (14 Units) a week might be a bit difficult to keep to, but at least you will now know what you should be aiming for!
For more information on how smokers can try to offset the negative health effects of direct smoking, see here.
It is very telling that the anti-smoking industry/health professionals do not advertise this information. Why? Surely their overall objective should be to improve the health of smokers and minimise future health costs for those who wish to continue smoking - for whatever reason? This demonstrates yet again that the smoking ban is nothing to do with health and all to do with appeasing those who dislike the smell of tobacco smoke.
Considering the actual risks associated with smoking puts them into perspective, and highlights the negligible effects that SHS will have on the long term health of non-smokers.
Lung cancer deaths attributed to smoking are cumulative year by year, but even for 100 people who have smoked 20 cigarettes a day from age 18 to 80, only around 16 or 17 will die from lung cancer! Hence 83 will NOT die from lung cancer. Smoking may be a risk factor, but it clearly isn't the only component.
Heavy exposure to SHS in the past (prior to 1998) has been defined as about 1/250th to 1/1000th of the smokers dose.
Hence, exposure to SHS will logically have no measurable effect on the long term health of non-smokers.