Passive Smoking - Where There's Smoke...

Since this is "Stop Smoking Week", an article on the effects of Passive Smoking seems appropriate. There is ample evidence of the damage active smoking does, but what is the impact of passive smoking, and is there good evidence to support the claims of its negative health effects.

In fact there are. The recent report of UK government's Scientific Committee on Tobacco and Health (SCOTH) concluded that that passive smoking is a cause of lung cancer, and that in those with long-term exposure the increased risk is 20-30%. It also concludes that passive smoking is a cause of ischaemic heart disease, of serious respiratory illness, asthmatic attacks, and middle-ear disease in children, and of the sudden infant death syndrome. ¹

A K Hackshaw² in an analysis of 37 published epidemiological studies of the risk of lung cancer (4626 cases) in non-smokers who did and did not live with a smoker, found compelling confirmation that breathing other people's tobacco smoke is a cause of lung cancer.

• A woman who has never smoked has an estimated 24% greater risk of lung cancer if she lives with a smoker
• Neither bias nor confounding accounted for the association
• There is a dose-response relation between a non-smoker's risk of lung cancer and the number of cigarettes and years of exposure to the smoker
• The increased risk was consistent with that expected from extrapolation of the risk in smokers using biochemical markers
• Tobacco specific carcinogens are found in the blood and urine of non-smokers exposed to environmental tobacco smoke
• All the available evidence confirms that exposure to environmental tobacco smoke causes lung cancer

The effect of passive smoking with respect to cardiac disease³ was studied by Ichiro Kawachi of the Harvard School of Public Health, who followed 32046 healthy, non-smoking women enrolled in the nurses health study for a period of 10 years (Circulation 1997;95:2374-9). He found that healthy, non-smoking women who reported regular exposure to passive smoke at home or in the workplace had a 91% greater relative risk of heart attack than those who reported minimal passive smoke exposure. Those who reported occasional exposure had a 58% greater relative risk.

The relationship between sudden infant death and maternal smoking was investigated by Peter S Blair, Peter J Fleming et al.⁴. Their study confirmed the increased risk of the sudden infant death syndrome associated with maternal smoking during pregnancy and showed evidence that household exposure to tobacco smoke has an independent additive effect. Parental drug misuse had an additional small but significant effect.

• Exposure of babies to tobacco smoke from other members of the household before or after birth increases the risk of death: the greater the exposure the higher the risk.
• Over 60% of such deaths may be attributable to the effects of exposure to tobacco smoke before and after birth.

It has been postulated that passive smoking causes more frequent and more severe attacks of asthma in children who already have the disease, and may increase the number of cases of asthma among children who have not had previous episodes. This hypothosis was confirmed by Chilmonczyk et al.⁵ in an article in the New England Journal of Medicine. Chilmonczyk used urine cotinine measurements as a biological marker of the exposure to tobacco smoke, and was able to demonstrate that acute exacerbations of asthma in children increase with exposure to second hand smoke.

It is apparent then that environmental smoke is a significant health hazzard. As physicians we should use this information to press for more smoke free public areas, and we must also make our patients aware of these risks to their own and their childrenšs health.

- John Hickey

1. Active Resistance to Passive Smoke Lancet Volume 351, Number 9106 21 March 1998
2. A K Hackshaw, M R Law, N J Wald, Papers: The accumulated evidence on lung cancer and environmental tobacco smoke. BMJ 1997;315:980-988 (18 October)
3. Deborah Josefson, Passive smoking doubles risk of heart disease BMJ 1997;314:1569 (31 May) News
4. Peter S Blair, Peter J Fleming et al. Smoking and the sudden infant death syndrome: results from 1993-5 case-control study for confidential inquiry into stillbirths and deaths in infancy, BMJ 1996; 313: 195-198
5. Chilmonczyk BA, Salmun LM, Megathlin KN, et al. Association between exposure to environmental tobacco smoke and exacerbations of asthma in children. N Engl J Med 1993;328:1665-9.

This page last updated February 14, 1999