How does Asbestos Cause Cancer
ASBESTOS AND CANCER: FOR HOW MUCH LONGER?
In 1998, Canada filed a complaint against to the World Trade Organization for non-compliance with international trade rules. To ban the purchase and use of asbestos to which Canada is the largest producer. Canada was dismissed because had shown so clear what the dangers of asbestos: asbestosis, cancer of the pleura (or "mesothelioma"), lung cancer. Given that the duration of induction of cancer by asbestos fibers may take several decades, we will probably hear about it for a long time.
We are often surprised to learn that asbestos is a completely natural product. It is a silicate of iron, magnesium and calcium (a mineral so) that forms flexible fibers, rot and fire resistant. It is found in large quantities especially in Canada which is the world's largest producer. The most common uses are the thermal and acoustic insulation for fiber "amphibole" and the manufacture of cement for fiber "chrysotile". This is where the rub, because it is now well established that amphibole fibers when inhaled, strongly favor the cancer of the pleura , the risk is disputed by the producing countries chrysoties for fiber cement. On this point, the experts Europeans for a very likely risk (difficult to quantify because the number of mesothelioma cases is comparatively small). Knowing that the mesothelioma or pleural cancer is almost always fatal within a few months at the cost of severe pain, the precautionary principle must of course play.
Diseases of asbestos
Exposure to asbestos can cause three types of pathologies. First, it can create a pulmonary fibrosis (asbestosis), leading to progressive respiratory failure. The second is cancer lung (but we know that tobacco is a risk factor even more important than asbestos). The third is the cancer of the pleura or "mesothelioma". It is not favored by the tobacco from 30 to 50% of cases are caused by exposure to asbestos. In all other cases, it is usually an occupational exposure (insulation, textiles, construction, filters) which is sometimes very short, sometimes very old (up to 40 years). The main sign of mesothelioma is the collection of fluid in the pleura causing pain and difficulty breathing. Diagnosis is made on the radio and scanner, which measures the degree of local invasion. To be certain about the diagnosis, it is necessary to take samples or by thoracoscopy pleuroscopy. Unfortunately the treatment is usually only palliative (chemotherapy and pain management). Death occurs within months.
A public health problem
In 1996, INSERM estimates the number of deaths related to asbestos (all diseases combined) in 1950, and for the period 1979-1990, the study of the incidence of cancers of the pleura showed an increase of 25 % every 3 years (Ministry of Labour and Social Affairs). The asbestos in question is the most amphibole asbestos, which has been used as insulation in a considerable number of buildings (eg Faculty of Jussieu). When we know that the time to onset of cancer of the pleura may be 40 years , is expected for several more years at a rate of cancers of the pleura.
