International Journal of Epidemiology 2001;31:700-701
© International Epidemiological Association 2001
Book Review |
The Health Effects of Chrysotile Asbestos: Contribution of Science to Risk Management Decisions
RP Nolan, AM Langer, M Ross, FJ Wicks, RF Martin (eds). Ottawa: Mineralogical Association of Canada, 2001, pp. 304, $US38. ISBN: 0-921294-41-7
This is the fifth Special Publication of The Canadian Mineralogist, produced by the Mineralogical Association of Canada (MAC). It presents the peer-reviewed proceedings of a 3-day International Workshop of the same title held in September 1997, in Montreal, Canada. The workshop was sponsored jointly by the MAC and the Mineralogical Society of America.
The preamble reveals that as long ago as 1978, the International Mineralogical Association ruled that the hyphenated terms grunerite-asbestos and riebeckite-asbestos be used instead of the ‘invalid’ terms ‘amosite’ and ‘crocidolite’, respectively (commonly known as ‘brown’ and ‘blue asbestos’, colloquial terms which are also recommended for abolition). This will be news to many scientists in this field. I wonder if the relative obscurity of the new hyphenated terms proves the case for retaining the old and familiar names that are, in fact, still in common usage. One is reminded of other convenient name changes and the public relations exercises behind them.
Professor Sir Richard Doll dedicates the book to Dr Robert Murray, an active participant of the workshop and one of the world's more colourful experts on asbestos-related disease. This is a poignant reminder of the controversial view, regularly expressed by Dr Murray before his death in 1998, that asbestos may have saved more lives in wartime situations as a result of its fire-resistant properties than it claimed in occupational settings. It is a pity that more effective legislation and protective gear were not organized in the mad rush to profitably exploit asbestos, although one would not expect a discussion of this important moral argument in the proceedings of such a conference.
The purpose of this monograph is reportedly to provide a scientific perspective to the historical era of high exposure to mixed asbestos (where the amphibole-group asbestos minerals of amosite, crocidolite and anthophyllite made up 5% of the asbestos used), and the modern era of controlled use of what is supposedly almost exclusively chrysotile (‘white’) asbestos in limited products, that will be useful in making risk-management decisions regarding the use of chrysotile asbestos. It appears oblivious to the fact that an increasing band of nations have successfully banned the importation and use of chrysotile (including the UK in 1999 and every country within the EU by 2002, except for Portugal and Greece who will be required to do so by 2005).
It could also be accused of downplaying the dangers of chrysotile given that the World Health Organization declared that chrysotile causes asbestosis, lung cancer and mesothelioma in a dose-dependent fashion (with no threshold) and alternatives should be used if at all possible. The World Trade Organization has declared that controlled use of chrysotile is not an effective alternative to a national ban. Perhaps the fact that this book is sponsored and published by the CMA, and that Canada has actively opposed the banning of chrysotile asbestos is relevant. The fact that Canada itself uses very little asbestos in manufacturing (preferring man-made mineral fibres), and exports 99.8% of the asbestos it produces (mostly to the developing world), is also relevant.
We can conclude from all the papers presented that historical occupational exposure tended to be very heavy and mixed resulting in mixed disease and will tend to be much lower and due to chrysotile only (unless inadvertently contaminated by amphibole fibre such as tremolite) in the future, resulting in a much lower risk of mainly lung cancer. But, is it as simple as that? Unpredictably high counts of mixed fibre that can still arise, particularly in the user, construction and demolition side of the industry, are not highlighted by this book which prefers to concentrate on the more easily controlled and therefore lower levels on the manufacturing side of the equation. This imbalance is featured in the reassuring and clear message that occupational exposure levels now, and in the future, should be low (<0.1 fibre/ml of ambient air) as a result of modern control technology and increasingly strict regulations emanating from health and safety legislation. In fact, we are told that the ‘best available technology’ should be able to achieve occupational levels of <0.02 fibres/ml. The risk of fibrotic or malignant lung disease developing from these exposure should be negligible. Nevertheless, occupational hygienists report instances of very much higher counts, particularly when asbestos materials are demolished or buildings renovated. Even more importantly, this entire issue is skirted over in the context of the developing world, the major consumer of both chrysotile and amphibole asbestos, where the concept of controlled use is regularly ridiculed by victim support groups, labour organizations and trade unions.
In addition, we are told that airborne concentrations of asbestos in buildings representing worst case scenarios and containing friable asbestos-laden fire-proofing material tend to be indistinguishable from outside air, suggesting that long-term, low-level environmental exposure from occupying suspect buildings is probably safe. Unfortunately, this is not supported by work from the Institute for Environment and Health at the University of Leicester. It reported levels of up to 0.3 fibres/ml in buildings where the asbestos material was in poor condition, in contrast to background ambient or outdoor levels of asbestos fibres which ranges up to 0.0001 fibres/ml.
Mesothelioma, a marker for previous asbestos exposure, continues to rise in the UK and predictions based on age-specific death rates suggest it will continue to do so for many years to come. This trend is assumed to have resulted from inadequate enforcement of health and safety protective legislation, confirming that significant exposure to mixed asbestos continued into the 1970s and perhaps later, and was experienced by workers in a range of occupations not covered by the legislation. When the use of crocidolite was discouraged by 1969 regulations the use of amosite expanded to fill the niche. With the widespread use of asbestos insulation board (40% amosite by weight) the exposed population expanded substantially. The importation and use of all amphibole fibre was banned in the UK as recently as 1985. Unfortunately, there is the continued occupational threat from the demolition of existing structures (particularly system-built flats clad, sprayed or partitioned between 1948 and 1980 with mixed asbestos). The men most likely to be occupationally exposed are those most likely to smoke, which will compound their risk of asbestosis and lung cancer.
The legacy of asbestos-related disease, that has yet to fully declare itself, is a result of inadequately controlled exposure to the most hazardous occupational hazard known to man. It is a great shame that, in their pursuit of the study of diseases of lifestyle, the public health community showed little interest while the scientific community neglected to take on board the ethical aspects of an industry that allowed hundreds of thousands of men to die with crippling or painful chest diseases, and usually in poverty. This monograph fails to provide a balanced view of both current and future exposure, particularly at an international level, and the resultant level of disease we might expect from it.
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