Malignant Pleural Mesothelioma Asbestos Mines and Cancer Mortality

Asbestos exposure carries a measurable risk of developing mesothelioma cancer.  Determining the point of exposure can be difficult sometimes.  Some workers are exposed as a consequence of their occupation, while others are exposed simply by living near a plant of mine.

One interesting study is called, "Multicentric study on malignant pleural mesothelioma and non-occupational exposure to asbestos" by C Magnani, A Agudo, C A González, A Andrion, A Calleja, E Chellini, P Dalmasso, A Escolar, S Hernandez, C Ivaldi, D Mirabelli, J Ramirez, D Turuguet, M Usel, and B Terracini  - Journal List - Br J Cancer  v.83(1); Jul 2000.  Here is an excerpt:  "Insufficient evidence exists on the risk of pleural mesothelioma from non-occupational exposure to asbestos. A population-based case–control study was carried out in six areas from Italy, Spain and Switzerland. Information was collected for 215 new histologically confirmed cases and 448 controls. A panel of industrial hygienists assessed asbestos exposure separately for occupational, domestic and environmental sources.

Classification of domestic and environmental exposure was based on a complete residential history, presence and use of asbestos at home, asbestos industrial activities in the surrounding area, and their distance from the dwelling. In 53 cases and 232 controls without evidence of occupational exposure to asbestos, moderate or high probability of domestic exposure was associated with an increased risk adjusted by age and sex: odds ratio (OR) 4.81, 95% confidence interval (CI) 1.8–13.1. This corresponds to three situations: cleaning asbestos-contaminated clothes, handling asbestos material and presence of asbestos material susceptible to damage. The estimated OR for high probability of environmental exposure (living within 2000 m of asbestos mines, asbestos cement plants, asbestos textiles, shipyards, or brakes factories) was 11.5 (95% CI 3.5–38.2). Living between 2000 and 5000 m from asbestos industries or within 500 m of industries using asbestos could also be associated with an increased risk. A dose–response pattern appeared with intensity of both sources of exposure. It is suggested that low-dose exposure to asbestos at home or in the general environment carries a measurable risk of malignant pleural mesothelioma."

Another interesting study is called, "An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy" by G Piolatto, E Negri, C La Vecchia, E Pira, A Decarli, and J Peto - Br J Ind Med 1990;47:810-814.  Here is an excerpt: "Abstract - The mortality experience of a cohort of chrysotile miners employed since 1946 in Balangero, northern Italy was updated to the end of 1987 giving a total of 427 deaths out of 27,010 man-years at risk. A substantial excess mortality for all causes (standardised mortality ratio (SMR) = 149) was found, mainly because of high rates for some alcohol related deaths (hepatic cirrhosis, accidents). For mortality from cancer, however, the number of observed deaths (82) was close to that expected (76.2). The SMR was raised for oral cancer (SMR 231 based on six deaths), cancer of the larynx (SMR 267 based on eight deaths), and pleura (SMR 667 based on two deaths), although the excess only reached statistical significance for cancer of the larynx. Rates were not increased for lung, stomach, or any other type of cancer. No consistent association was seen with duration or cumulative dust exposure (fibre-years) for oral cancer, but the greatest risks for laryngeal and pleural cancer were in the highest category of duration and degree of exposure to fibres. Although part of the excess mortality from laryngeal cancer is probably attributable to high alcohol consumption in this group of workers, the data suggest that exposure to chrysotile asbestos (or to the fibre balangeroite that accounts for 0.2-0.5% of total mass in the mine) is associated with some, however moderate, excess risk of laryngeal cancer and pleural mesothelioma. The absence of excess mortality from lung cancer in this cohort is difficult to interpret."

A third study worth examining is called, "The interactions between asbestos fibers and metaphase chromosomes of rat pleural mesothelial cells in culture. A scanning and transmission electron microscopic study." By N. S. Wang, M. C. Jaurand, L. Magne, L. Kheuang, M. C. Pinchon, and J. Bignon - Am J Pathol. 1987 February; 126(2): 343–349.
Here is an excerpt: "Rat pleural mesothelial cells (PMCs) in culture at the exponential growing phase were exposed to 5 micrograms/ml of chrysotile (CH) or crocidolite (CR) asbestos fibers: the cells and their chromosomes were studied 48 hours thereafter by light, scanning, and transmission electron microscopy (LM, SEM, TEM). PMCs phagocytized both CH and CR. Mild vacuolar cytoplasmic changes by LM and a few small surface blebbings by SEM were present, mainly in cells treated with CH. Metaphase chromosomes were well separated and retained surface details by SEM in the control group. Chromosomes were frequently entangled with, adherent to, and severed or pierced by long and thin curvilinear CH with occasional chromatin fibers threading over the partly severed asbestos. Similar chromosomal changes were much less frequently found in CR-treated cells; TEM confirmed the same findings. CH and CR have different physicochemical properties and also appear to have direct, intricate, but different interactions with chromosomes, as well as the cytoplasm, of PMCs."

If you found any of these excerpts interesting, please read the studies in their entirety.  We all owe a great debt to these researchers for their important work.