Monday, January 10, 2011

Is Asbestos Killing 100,000 people a year?

A careful examination of studies shows that this statement is grossly misleading and represents only selective parts of the scientific info.

Very often, the anti-asbestos lobby justify its campaign against the use of asbestos by the figure that 100 000 people dies annually from the exposure to this mineral. Even the World Health Organization (WHO) and the International Labour Organization (ILO) seem to have accepted this data as a fact.

First of all this estimate is based on data collected from European countries and extrapolated to the rest of the world. This approach is not taking into account different fibre types, structure and composition of the industry and past uncontrolled heavy exposures. Hence, a simple extrapolation is inaccurate and it could lead to considerable overestimation.

Manfred Neuberger and Christian Vutuc in their article 'Three decades of pleural cancer and mesothelioma registration in Austria where asbestos cement was invented', Int Arch Occup Environ Health (003 ) 7 6: 61 -66.) stated:
'Uncritical extrapolation of results from countries with а high incidence of asbestos-induced mesothelioma to countries with а low incidence could be harmful, because in countries with а low incidence other risk factors of mesothelioma [6, 11, 12, 19, 20, 23, 33, 34] of possible higher future importance could be investigated only if self-fulfilling prophecies do not disturb the investigations.'
“The calculations made use of some questionable indicators for under- and over diagnosis and of ratios such as excess lung cancer to mesothelioma in historical cohort studies which, in fact, differed largely between countries and periods due to different cumulative exposures and different uses of amphibole asbestos.”
In fact figures about 00 000 deaths were derived from papers Driscoll T et al1 , and Concha-Barrientos M et al2. But these authors clearly differentiate risk from types of asbestos.
“Assuming a mixed fibre type, the lifetime risk of death from malignant mesothelioma is approximately 100 per 100 000/fibre.year per ml. (This combined estimate is based on best estimates of risk of 400 per 100 000/fibre.year per ml for crocidolite, 65 per 100 000/fibre.year per ml for amosite and 2 per 100 000/fibre.year per ml for chrysotile, and the changing mixture of amphiboles and chrysotile that has characterised exposure 20 and 50 years ago [Hodgson and Darnton, 2000].)”
(Driscoll Tetal, “The global burden of disease due to occupational carcinogens”, 2005, page 7)
On the page 1687 of paper Concha-Barrientos M et al. “Selected occupational risk factors. Comparative quantification of health risks: global and regional burden of diseases attributable to selected major risk factors” author state:
“In 20 studies of over 100,000 asbestos workers, the standardized mortality rate ranged from 1.04 for chrysotile workers to 4.97 for amosite workers, with a combined relative risk of 2.00. It is difficult to determine the exposures involved because few of the studies reported measurements, and because it is a problem to convert historical asbestos measurements in millions of dust particles per cubic foot to gravimetric units. Nevertheless, little excess lung cancer is expected from low exposure levels.”
Knowing the fundamental differences between the several asbestos fibre types, stating “Asbestos kills 100,000 workers every year” is not only unscientific; it is nonsense.
What would be the basis to affirm that «chemicals kills x workers» or «metals are responsible for the death of x workers»? Nonsense. Chemical and metals include a wide variety of products with different properties, uses and health risk.
It is the same with asbestos. There is no justification to put in the same basket the health risk of being exposed to chrysotile and to amphiboles fibres. In their review of many scientific studies about workers exposed to various types of asbestos, Hodgson and Darnton (2 000) estimated that the risk for lung cancer from working with amphiboles is 100 times what it is for chrysotile. In fact, the 100 000 death estimates is established form a «combined relative risk» for asbestos, therefore attributing a mortality ratio from exposure to amphiboles to workers working with chrysotile. As logical as saying that a mix of water and poison would kill people; half of them from the ingesting the poison, the other half from water!
Moreover, the 100,000 deaths estimate does not take into account the fact that exposure levels have dramatically decreased in the last decades.
Undoubtedly, bad work conditions and the use of various amphiboles fibres have causes diseases among asbestos workers. Because of the latency period, the diseases appearing today are the results of exposures that were encountered 20 to 40 years ago.
In fact, the rate of asbestos related diseases have started to decline, thanks to the improvement in working conditions implemented from the 1970’s and the prohibitions of amphiboles in the late 1980’s. The concern today is the presence of amphiboles and friable products in buildings that have to be properly managed in order to prevent the apparition of industrial diseases. To do so, proper information, good work practices and appropriate control measures — not a blind prohibition — will help to achieve this objective.
The 100,000 death figure is misleading, because it implies that asbestos is used nowadays in the same way it was managed 50 years ago.

And yet, many scientific studies published in the last 25 years have shown that the rates of industrial
diseases of workers of the asbestos-cement industry — which accounts for 90% of the use of chrysotile in the world today — do not exceed the national average.
The Risk of Projection

In the 1980’s, the U.S. EPA established a model for asbestos related diseases in relation with the number of workers exposed. This model gave dramatic numbers, leading to a series of measures that were not related to the nature of the problems. The U.S. Congress passed the Asbestos Hazard Emergency Response Act (AHERA) in 98 6. It ordered school districts to locate all asbestos in their buildings and create a plan to manage it. It also imposed tight regulations on asbestos removal, raising costs and ensuring that the image of asbestos removal workers in spacesuits would keep fears high.

AHERA requirements have cost an estimated $50 billion over the past 0 years. In was found that the absence of excess lung cancers among residents of chrysotile mining towns implies a risk at least 5 times smaller than that predicted with the EPA model, and the number of mesotheliomas observed is at least 0 times smaller than that predicted by the EPA model. In 990, the EPA issued the Green Book, which said asbestos in schools and offices presented a low risk. It noted that improper asbestos removal could increase exposure by stirring up dust unnecessarily.
However, the EPA has never sustained an effort to reverse the multibillion-dollar asbestos removal effort that its early pronouncements sparked.

Why have billions been spent attacking a minor health risk?

The experts say the fear created by the health tragedy that befell asbestos workers — real and projected numbers — and the multibillion-dollar lawsuits that followed had overwhelmed the scientific evidence.

No one can stop denigration campaign lead by parties having an interest with the prohibition of chrysotile, but it has thus become disturbing that inside both the WHO and the ILO, some people in key positions are embarking on a campaign for a global ban of asbestos based on a very selective and partial reading of the evidence.

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