Asbestos Exposure And The Increased Risk Of Carcinoma

Mesothelioma is a deadly disease that has taken thousands of lives. The more public awareness that is brought to this disease, the better. One interesting study is called, Unsuspected exposure to asbestos and bronchogenic carcinoma by K M Martischnig, D J Newell, W C Barnsley, W K Cowan, E L Feinmann, E Oliver - Br Med J 1977;1:746-749 (19 March). Here is an excerpt: Two hundred and fifty men admitted to a thoracic surgical centre and matched controls were questioned in detail about their occupations after leaving school and their smoking habits. Of 201 men with confirmed bronchial carcinoma 58 gave a history of occupational exposure to asbestos, whereas only 29 out of 201 men matched for age and residential area who were admitted with other diseases gave such a history. This difference was statistically highly significant. The usual association of bronchial carcinoma with heavy smoking was observed, but asbestos exposure increased the risk of carcinoma whatever the level of smoking. These results are consistent with the hypothesis that asbestos exposure and the level of smoking act independently in causing bronchial carcinoma. The patients with carcinoma who had been exposed to asbestos presented on average three years earlier than those who had not been exposed. Asbestos regulations have eliminated the risk of exposure to workers in scheduled industries, so asbestos-induced diseases will probably be increasingly found among the many workers who have had incidental exposure to asbestos. It is therefore important to take a full occupational history.

Another interesting study is called, Asbestos and mesothelioma: Worldwide trends by Laurie Kazan-Allen - Volume 49, Supplement 1, Pages S3-S8 (July 2005). Here is an excerpt: Summary - A correlation between national asbestos consumption and the incidence of asbestos disease, including mesothelioma, has been observed. Towards the end of the 20th century, governments in many developed countries banned or seriously restricted the use of asbestos. As a result, global asbestos producers have engaged in aggressive marketing campaigns to sell asbestos to developing countries; consumption of white asbestos is increasing in Asia, Latin America and the Commonwealth of Independent States. In most of the countries, there is little, if any, control on hazardous asbestos exposures from occupational, environmental and domestic sources. It is likely that the lethal asbestos harvest which is occurring in the U.S., the UK and Australia will be reproduced in the developing world.

A third study worth examining is called, Response of mouse lung to crocidolite asbestos, Minimal fibrotic reaction to short fibres by Dr Ian Y. R. Adamson, Drummond H. Bowden - Department of Pathology, University of Manitoba, Winnipeg, Canada - The Journal of Pathology Volume 152 Issue 2, Pages 99 107. Here is an excerpt: Abstract - To determine the relationship between the development of pulmonary fibrosis and the size of deposited asbestos, we prepared a pure sample of short crocidolite fibres and instilled 0.5 mg of 0.1 mg to the lungs of mice. Animals were killed up to 20 weeks later with 3H thymidine injected 1 h before death. By bronchoalveolar lavage, there was a rapid transient increase in polymorph neutrophils (PMN) and in glucosaminidase levels; alveolar macrophage (AM) numbers were elevated in the 0.5 mg group for eight weeks. Most fibres were phagocytized by AM, many of which were heavily laden and cleared from the lung over the 20 week period. Some fibres were seen in type 1 epithelial cells, frequently associated with cell injury. From cell kinetic studies, a very brief proliferative response was seen in bronchiolar epithelial and Type 2 alveolar epithelial cells. A greater response was seen in interstitial fibroblasts which showed increased labelling up to two weeks after 0.5 mg asbestos. However no granulomas were seen and very little fibrosis was found by morphology or by biochemistry at any time after 0.5 mg; no fibrosis was seen after instilling 0.1 mg. The results show that a high dose of exclusively short asbestos fibres produces minimal lung injury and fibrosis in spite of long standing macrophage-fibre interaction in the alveoli.

If you found any of these studies interesting, please read them in their entirety. We all owe a great deal of thanks to the people who are researching these important issues.