Asbestos Exposure Concerns
- Asbestos Lung Disease
What is Mesothelioma?
"Mesothelioma (malignant)"
Mesothelioma is a rare form of cancer. It affects the linings of the cavities around the lungs, stomach, and heart. It is caused by inhaling asbestos fibers, but the cancer usually does not appear until 10 to 40 years after a person first inhales asbestos.
Exposure Concerns
Table 10 shows the same calculations on the basis of the risk assessment by the NRC/NAS (65). Applying the same level of acceptable risk (1 x 10 -5) and using the number of estimated deaths from mesothelioma and lung cancer for male smokers and nonsmokers at the assumed asbestos concentration of 400 fibres per cubic meter, the respective calculated exposure limits are 9 and 22 fibres per cubic meter.
In other words, these limits require a nearly 10-fold reduction of asbestos fibre levels in rural areas without specific asbestos emission! It is obvious that mathematical extrapolations
CONCLUSIONS
There is no doubt that fibres of all the prevalent forms of asbestos can cause lung cancer and mesothelioma. The weight of evidence convincingly suggests that amphiboles are more potent carcinogens than chrysotile.
No threshold has been identified for any of the types of asbestos except possibly for chrysotile; a practical threshold was found in chrysotile mining operations, in the manufacturing of chrysotile friction products and in some cohorts of workers in asbestos-cement production.
The unit risks, estimated in studies acceptable as regards the number of examinees, the duration of follow-up and the quality of data vary by several orders of magnitude. To a large extent, this is the consequence of considerable uncertainty in the estimates of past exposure levels due to errors in conversion from weight (mg/m3) or count (mppcf) concentrations of total particles to the currently used count concentrations of defined fibres.
The practical application of unit risks of such uncertainty leads to unachievable exposure limits. In spite of hundreds of papers published on asbestos health effects, there are still important unresolved issues. The effects seen today are the consequence of uncertain exposure of 20-50 years ago.
It cannot be predicted with any degree of certainty what will the consequences of the current, incomparably lower exposure levels be in the future. Yet, there is no doubt that it is advisable to replace any potential carcinogen with noncarcinogenic or less carcinogenic material whenever possible.
At this point in time, however, there are few materials of known toxicity / carcinogenic and at least equal technological performance. There is a potential for the development of such materials, but their toxicological properties have not been evaluated sufficiently. This is the main problem the world is facing on the eve of the possible worldwide asbestos ban, which will be considered in the second part of this paper:
'The Asbestos Dilemma: II. The Ban". of asbestos risk lead to unfeasible threshold limit values.
People exposed to asbestos fibers are at risk of developing an asbestos lung disease. Asbestos lung disease typically has a high fatality rate. People with asbestosis are more likely to develop asbestos lung cancer; smokers exposed to asbestos are 55 times more likely to develop asbestos lung cancer than non-smokers.
The sharp rise in asbestos litigation could be attributed to increased public awareness about the harmful effects of asbestos and related diseases.