Passive smoking: what are the limits to liberty?

Approximately one-quarter of adult Australians are "active" smokers, but almost everyone is a "passive" smoker at some time. The right of adults to make a fully informed decision to begin or to continue smoking is not in question, but there is widespread concern about the risks carried by non-smokers who breathe environmental tobacco smoke (ETS) from others' cigarettes. If passive smoking really does harm health, then a strong case can be made for limiting the places and situations in which smoking is permitted.

In November 1995, the National Health and Medical Research Council (NHMRC) released for public comment a new report on the effects of passive smoking on health.¹ It reviewed the scientific evidence on the risks to health from exposure to ETS, gave an estimate of the total burden of illness attributable to passive smoking in Australia, and gave 25 recommendations for measures to reduce this burden. (The main recommendations are shown in the Box.)

The report concluded that the evidence relating ETS to several important categories of illness had strengthened considerably since the last NHMRC review in 1986.² It found that ETS is firmly linked, as a likely causal factor, to lower respiratory tract illness in young children, asthma, lung cancer and cardiovascular disease, and provided detailed calculations of the numbers and costs of additional cases of these conditions attributable to passive smoking in Australia.

Evidence since 1986 implicates exposure to ETS as a cause of sudden infant death syndrome, "glue ear" in childhood, acute irritation of the respiratory tract, and low birth weight (as a consequence of non-smoking mothers being exposed to ETS during pregnancy). However, the report found insufficient evidence concerning these conditions to include them in estimates of the burden of illness.

Each year, according to the NHMRC report, passive smoking leads to more than 5400 extra hospital admissions in Australia and costs the country about $21 million. The brunt of this excess morbidity -- 51 600 episodes of asthma (about 9% of all cases) in people aged less than 15 years, and about 2000 admissions to hospital in the first 18 months of life because of chest illness -- is borne by children. There are approximately 10 attributable cases of lung cancer among adults who have never smoked and 100 deaths from coronary disease.

These figures are likely to be underestimates. The effects of passive smoking on current and ex-smokers have not been included, any effects of low levels of exposure in causing or exacerbating asthma have been ignored, and it has been assumed that passive smoking does not cause other respiratory problems in children over 18 months of age. Evidence from overseas indicates that the burden of adult illness from exposure outside the home is likely to be at least as great as that from domestic exposure,³ but the NHMRC estimates include domestic exposure only.

The term "passive smoking" was coined 25 years ago,⁴ but scientific and public interest in the issue accelerated sharply in 1981 when Hirayama published evidence that exposure to ETS went beyond being a source of annoyance to non-smokers and actually caused lung cancer.⁵ The NHMRC working party was able to find 31 separate studies of ETS and lung cancer in non-smokers published before 1995, as well as 41 investigations of the impact of passive smoking on various respiratory complaints in childhood.

As the report by Doyle et al. in this issue of the Journal shows, the evidence linking ETS with impairment and illness continues to grow. This prospective study of a cohort of very low birthweight children found that those who had been exposed to tobacco smoke since birth had worse respiratory function than their non-exposed peers when tested at 11 years of age. The findings exhibit a dose-response relationship, despite a somewhat crude assessment of exposure to ETS, and cannot be explained by differences in the socioeconomic circumstances. The results are based on small numbers of children, but are consistent with other published studies. It should be noted also that active smokers never regain the decrement in respiratory function that they accumulate, even if they give up smoking.⁶ There is a clear message to doctors and parents: passive smoking is the most readily preventable cause of respiratory impairment in childhood.

Vulnerable groups in society -- infants, children and adults with asthma and other respiratory conditions, and individuals with established cardiac disease -- are most affected by exposure to ETS. Workplaces where smoking is still allowed, including hotels and restaurants, are also a special case because the passive smoking by employees in these enterprises is often involuntary. Progress has been made in the provision of smoke-free workplaces, but about 40% of Australian indoor workers are still exposed to tobacco smoke at work.⁷

What is now the appropriate public policy response to more than two decades of careful scientific research into the risks associated with passive smoking? We probably can do little better than be guided by John Stuart Mill's oft-quoted essay On liberty:⁸

"The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others."

Alistair Woodward
Professor of Public Health
Wellington School of Medicine, New Zealand

Konrad Jamrozik
Associate Professor, Department of Public Health
University of Western Australia

References

1. National Health and Medical Research Council. The health effects of passive smoking: The draft report of the NHMRC Working Party, November 1995. Canberra: NHMRC, 1995.
2. National Health and Medical Research Council. Effects of passive smoking on health. Canberra: AGPS, 1987.
3. United States Environmental Protection Agency. Respiratory health effects of passive smoking: lung cancer and other disorders. Washington DC: Office of Research and Development, 1992.
4. Harke HP. Zum problem des "passiv-rauchens". Munch Med Wochenschr 1970; 51: 2328-2334.
5. Hirayama T. Nonsmoking wives of heavy smokers have a higher risk of lung cancer: a study from Japan. BMJ 1981; 282: 183-185.
6. Fletcher CM, Peto R. The natural history of chronic airflow obstruction. BMJ 1977; 1: 1645-1648.
7. Borland R, Mullins R. The increasing prevalence of workplace smoking bans in Victoria, 1994. J Occup Health Safety Aust N Z 1994; 10: 35-40.
8. Mill JS. On liberty. London: Watts & Co., 1941: 11.