Mesothelioma Info - Asbestos Exposure, Mesothelioma Lawyer
Asbestos, Mesothelioma Epidemiological Data
In man the link of lung cancer with asbestos has been mainly epidemiological. While asbestosis cannot occur without exposure to asbestos and consequently every case of asbestosis must be linked with such exposure, with pulmonary cancer the situation is quite different. It is a rather common disease in the general population. The link with exposure to asbestos is based on finding whether in those exposed to asbestos lung cancer occurs more frequently than in those unexposed, i.e. whether in those exposed there is an excess incidence of lung cancers.
Since Doll's study a number of other epidemiological studies, of various levels of excellence, have been carried out which confirm that indeed there is an excess of bronchogenic carcinoma in persons exposed to asbestos, under certain circumstances, and thus that asbestos must be considered one of a number of carcinogenic substances.
What are the circumstances of a manifest risk of cancer in asbestos exposure? It has been established that smoking cigarettes greatly increases this risk. In fact the large majority of lung cancers attributed to asbestos exposure have occurred in smokers. A lung cancer in an asbestos-exposed non-smoker has been a rarity. Table 1 shows the effect of both exposures together, while each of the two exposures also carries a risk by itself. A particular exposure to asbestos in the reported group of workers increased the basic risk of pulmonary cancer in non-smokers. However, since the risk in non-smokers was very small, its further increase still meant only very few cases, if any at all. On the other hand, when the basic risk of exposure to asbestos was combined with the 11.8 times higher risk of a smoker, this combination necessarily produced a serious risk leading to an excess of incidence of pulmonary cancer. This experience has an important practical implication: most "asbestos cancers of the lungs" could be prevented if the workers did not smoke. In fact it was found that the risk for the asbestos workers who had stopped smoking declined after 10 years to the low level existing for non-smokers.
The bronchogenic carcinoma has a long latent period, usually 20 years or more. Consequently, what excesses of incidence of pulmonary carcinoma linked with asbestos have been found to date must be linked with exposures 20 years or more before development of the tumour. It is known that exposures in those days were generally very high. But we usually do not have any precise measurements. Thus in most existing epidemiological studies it has not been easy, and in some not possible, to establish a relation between the incidence of cancer and a certain quantitative level of exposure, other than that the exposure had been high.
| Asbestos exposure | |||
| Little | Moderate | Heavy | |
|---|---|---|---|
| Non-smokers | 1.0 | 2.0 | 6.9 |
| Moderate smokers | 6.3 | 7.5 | 12.9 |
| Heavy smokers | 11.8 | 13.3 | 25.0 |
| From: McDonald, J. C. "Asbestos-related diseases: an epidemiological review" (587-601). Biological effects of mineral fibres. Wagner, J. C. (ed.). IARC scientific publications No. 30 (Lyons, International Agency for Research on Cancer, 1980), Vol. 2. | |||
One quantitative measure commonly used is the duration of exposure in years. In other studies the period since first exposure is used, and in yet others, both the period since first exposure and the duration of exposure. Only a few investigations have had the additional benefit of actually measured data on past levels of exposure. An example of the latter is the series of epidemiological studies of workers of the chrysotile mines of Quebec carried out by J. C. McDonald and his collaborators. This and some other studies showed a dose-response relationship, i.e. the higher was the dose, in terms of level of exposure, or of periods of exposure, or of both of them combined, the higher was the excess incidence of bronchogenic cancer. In fact the excess incidence of lung cancer and statistically significantly increased relative risk was usually found only in groups of persons most severely exposed (see table 2).
Table 2. Relative risks of lung cancer in relation to accumulated dust or fibre exposure, before and after correction of work histories, with controls matched for smoking.
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Accumulated dust exposure
(millions of particles per cubic foot x years)
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< 30 30 300 > 1000 All
< 300 < 1000
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Before correction
Cases 89 73 56 27 245
Controls 108 87 42 8 245
Relative risk 1 1.02 1.62 4.10 --
After correction
Cases 85 73 59 27 244
Controls 101 89 44 10 244
Relative risk 1 0.97 1.59 3.21 --
Accumulated fibre exposure
(fibres per ml x years)
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< 100 100 1 000 >3 000 All
< 1 000 <3 000
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| From: McDonald, J. C.; Gibbs, G. W.; Liddell, F. D. K. "Chrysotile fibre concentration and lung cancer mortality: a preliminary report" (811-817). Biological effects of mineral fibres. Wagner, J. C. (ed.). IARC scientific publication No. 30 (Lyons, International Agency for Research on Cancer, 1980), Vol. 2. __ |
Mesothelioma Info
Malignant mesothelioma asbestos is a rare type of cancer that affects the mesothelial tissue lining of three large bode cavities. There are three distinct types of mesothelioma cancer: pleural mesothelioma (the most common type), peritoneal mesothelioma and pericardial mesothelioma.
Benign fibrous mesothelioma was once viewed as a non-malignant type of pleural mesothelioma; however, it is now known that mesothelioma is by nature malignant, and therefore cannot exist in a benign form. Any reference to a benign fibrous mesothelioma is an erroneous classification.
If you or a loved one has been diagnosed with malignant mesothelioma, contact an asbestos attorney or mesothelioma lawyer to get information about your right to compensation.
Increased public awareness of malignant mesothelioma has helped to pave the way for an increase in mesothelioma litigation. Clinical trials are ongoing for chemotherapy drugs Veglin and Onconase.