Epidemiology of Asbestos-Induced Mesotheliomas

Asbestos-Induced Mesotheliomas

Asbestos, a group of different chemical and physical fibers, is one of the most well-known carcinogens in the lungs and pleura. The 1978 National Institutes of Health estimated that about 11 million people have been exposed to asbestos in the United States since 1940.

Although widely used in World Wars I and II, the use of asbestos has undergone major changes in recent decades, with strict restrictions in most countries on amphibians. 

In developed countries, with the exception of Japan, asbestos production is controlled or prohibited, while in developing countries, consumption has leveled off or increased. 

Between the 1940s and 1970s, asbestos was used extensively in insulation applications (especially in the building construction industry), and in asbestos cement pipes. Current use is generally limited to chrysotile in four products: asbestos cement, friction materials, roofing coatings, cement blocks, and gaskets. In 1992 about 28 million tons of asbestos cement products were produced in about 100 countries.

Properties of asbestos fibers

Asbestos is a group of natural fibers, each with its own unique structure and chemical composition (Table 2.1). There are two subgroups: (1) The Serpentine group, composed of chrysotile; and (2) amphiboles, a group of rod-like fibers including crocidolite, amosite, tremolite, anthophyllite, and actinolite (4). Asbestos fibers are ubiquitous in certain geographic areas and become a problem for human health when inhaled. It is not clear how they get to the pleura to cause mesothelioma.

Epidemiology of asbestos-induced mesothelioma

The most important causative factor for the development of human mesothelioma is exposure to asbestos, especially amphiboles crocidolite and amosite. Malignant Mesothelioma is currently a worldwide problem. 

Although mesothelioma is a rare disease, with an annual incidence in the United States of 2000 to 3000 cases, a steady increase in cases has been reported. In Europe, the incidence of Malignant Pleural mesothelioma has been increasing for decades and is expected to peak between 2010 and 2020 (7). In Germany, a study conducted on 1605 patients on the mesothelioma register (1987-1999), found that 70% had a history of asbestos exposure. 

In the UK, asbestos reportedly accounts for about 600 cases of mesothelioma and 100 cases of bronchial carcinoma per year. The incidence of mesothelioma has increased rapidly and is expected to increase even more from the current total of 1300 to more than 3000 cases per year. Fiber exposure is associated with most of these cases.

The link between amphibole asbestos exposure and pleural mesothelioma is the result of the pioneering work of Wagner and colleagues (11), who found a link between the high incidence of dis-ease and people working in or living near crocidolite asbestos mines (blue), with intermediate disease rates near amosite mines, and no tumors in chrysotile miners.

Lung load studies have also confirmed that the asbestos amphibole subgroup (crocidolite, amosite) is more strongly associated with the development of malignant mesothelioma and lung cancer. In a recent study on 1445 cases of mesothelioma in the United States, it was determined that commercial amphiboles were responsible for most of the observed cases of mesothelioma. 

Chrysotile asbestos can produce mesothelioma in humans, but the number of cases is small and the exposures required are large. Heavy exposure to chrysotile asbestos alone, or with negligible amphibole contamination, can cause malignant mesothelioma and other lung cancers in humans, but studies evaluating working populations that are temporary and can be exposed to different types of fibers over a lifetime are difficult to interpret.

Several studies have implicated tremolite fibers as a possible etiological factor in mesothelioma associated with exposure to chrysotile. However, others suggest that chrysotile does not cause mesothelioma, although it may be much stronger than amphibole asbestos (18).

Although the relationship between amphibole asbestos exposure and the development of malignant mesothelioma is well documented, available information suggests that other factors contribute to its etiology. Some studies suggest that genetic factors can play an important role in the etiology of the disease. 

Also, an interesting multi-institution study showed that SV40 (t) - antigen (Tag) tumors are present in a large percentage of human mesotheliomas. About 60% of mesotheliomas in the United States are positive for the SV40 tag.

Asbestos properties linked to carcinogenic potential

The carcinogenic potential of asbestos fibers has been attributed to their geometry, size, and chemical composition. Due to the potential increase in long fibers (>5 mm) causing mesothelioma and fibrosis after intrapleural or intraperitoneal administration in rodents, the health problems for long fibers that can be inhaled [World Health Organization (WHO) criteria: length >5mm, diameter.

Source

Harvey I. Pass, Nicholas Vogelzang, Michele Carbone - Malignant Mesothelioma_ Pathogenesis, Diagnosis, and Translational Therapies-Springer (2005)

Berlangganan update artikel terbaru via email:

0 Response to "Epidemiology of Asbestos-Induced Mesotheliomas"

Post a Comment

Iklan Atas Artikel

Iklan Tengah Artikel 1

Iklan Tengah Artikel 2

Iklan Bawah Artikel