Sydney's asthma witch huntBMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7017.1390a (Published 25 November 1995) Cite this as: BMJ 1995;311:1390
Sydney has long suffered a reputation as an otherwise beautiful city blighted by an almost permanent pall of brown haze. With an appalling public transport system servicing a vast city with low housing density, car travel has always been the norm. Civic, commercial, and tourism interests are concerned that the haze should not tarnish the city's reputation when it hosts the Olympic games in 2000. Thus the National Roads and Motorists Association, supported by several major companies and government departments, has embarked on a five year publicity campaign seeking to “clear the air” via strategies such as telecommuting and car pooling.
Public health groups have been drawn into the debate because health provides an imperative to match the aesthetic objections to smog. There is an indomitable assumption that the haze must be a factor underlying the huge increases in asthma rates. A recent survey of over 6000 primary school children found that one third had been diagnosed as having asthma, compared with 11% 10 years ago.
Air pollution has been fingered by the public and the media as the obvious villain, while many in public health remain unconvinced. Early next year the results of a major epidemiological investigation into the relation between Sydney's air quality and the incidence of asthma will be published. The study had its origin in two highly publicised “smog summits” convened by the then New South Wales premier Nick Greiner in 1991 and 1992. The summits were precipitated by a series in a Sydney tabloid newspaper. The theme of the reports was that people in Sydney lived under a worsening cloud of atmospheric pollutants; that these were causing an epidemic of asthma; that government authorities were, ostrich-like, unable to see the problem that was obvious to the ordinary person; and that generally, government should “do something” about it.
If the epidemiological research concludes--like the recent British report from the Committee on the Medical Effects of Air Pollutants (28 October, p 1120)-- that the contribution of air pollution to the asthma epidemic is weak, uncertain, or equivocal, major challenges will arise for epidemiology. Those involved will need to consider how to ensure the credibility of such findings and to fend off innuendo about epidemiologists being lapdogs of government and the oil and motor industries.
Much will depend on the way that those who have to explain the epidemiological findings can anticipate the predispositions of journalists. Interviews with Sydney health and environmental journalists confirm how entrenched the link between asthma and air pollution has become. One radio reporter told me, “If you think of smog, you think of breathing and you think of health. So whenever you get a smog story, you obviously put a health angle to it.” Another said, “I think the next time there's heavy pollution days [journalists] will ring around the hospitals and say ‘Do you have a lot of asthmatics in?' and if someone says yes, then it's front page news. You can have five people say no, but if someone says yes, you have a story.”
Associate Professor Craig Mellis, from the New Children's Hospital at Westmead, told a recent meeting of the Royal Australasian College of Physicians that increases in the standard of living, and smaller family sizes, may be largely responsible for the increase in the incidence of asthma: the repeated respiratory infections that used to occur in early childhood (but have now reduced considerably) may have had a protective effect against asthma. Such hypotheses, along with efforts to reduce exposure to dust mites, are being explored in a comprehensive research programme now under way in several Australian research institutions.
Those who criticise simplistic associations between air pollution and asthma risk being politically incorrect. Sydney's journalists, its public (77% believe that air pollution increases asthma rates), and the business community involved in the clean air campaign have made up their minds.
When epidemiology clashes with common sense in contemporary witch hunts an evidence based resolution is unlikely.
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