Asbestos is a group of naturally occurring fibrous minerals which are commercially used for insulation in buildings and as an ingredient in a number of products such as roofing tiles, water supply lines, and fire blankets, as well as clutches and brake linings, gaskets, and pads for automobiles. Asbestos causes cancer and chronic respiratory diseases in humans.
All forms of asbestos (chrysotile, crocidolite, amosite, tremolite, actinolite and anthophyllite) are in use because of their extraordinary tensile strength, poor heat conduction, and relative resistance to chemical attack. Chemically, asbestos minerals are silicate compounds, meaning they contain atoms of silicon and oxygen in their molecular structure.
All forms of asbestos are carcinogenic to humans. Exposure to asbestos (including chrysotile) causes cancer of the lung, larynx, and ovaries, and also mesothelioma (a cancer of the pleural and peritoneal linings). Asbestos exposure is also responsible for other diseases such as asbestosis (fibrosis of the lungs), and plaques, thickening and effusion in the pleura.
Exposure to asbestos occurs through inhalation of fibers in air in the working environment, ambient air in the vicinity of point sources such as factories handling asbestos, or indoor air in housing and buildings containing friable asbestos materials.
According to World Health Organization estimates about 125 million people in the world are exposed to asbestos at the workplace. At least 107000 people die each year from asbestos-related lung cancer, mesothelioma and asbestosis resulting from occupational exposures. Approximately half of the deaths from occupational cancer are estimated to be caused by asbestos. In addition, it is estimated that several thousand deaths annually can be attributed to exposure to asbestos in the home.
It has also been shown that co-exposure to tobacco smoke and asbestos fibers substantially increases the risk for lung cancer and the heavier the smoking, the greater the risk.
Asbestos is still widely used in Asian countries. Asbestos deposits are found in Andhra Pradesh, Bihar, Jharkhand, Karnataka, and Rajasthan. In India, the domestic consumption of asbestos is 1.25 lakh tones annually, out of which more than a 1.0 lakh tonnes is being imported. Significant occupational exposure to asbestos occurs mainly in asbestos cement factories, asbestos textile industry and asbestos mining and milling. National Institute of Occupational Health (NIOH), Ahmedabad, has carried out environmental and epidemiological studies in cement factories, asbestos textile industry and asbestos mining and milling with the following observations-
· The prevalence of asbestosis in four cement factories (Ahmadabad, Hyderabad, Coimbatore and Mumbai) varied from 3% to 5%.
· In asbestos textile industry prevalence of asbestosis was 9% in workers having less than 10 years exposure, in contrast to the reported average duration of over 20 years. Exposure to asbestos fibers is quite high in these industries (216-418 fibers/ml as compare to permissible limit of 2 fibers /ml).
· The overall prevalence of asbestosis in mining and milling units was 3% and 21% respectively. In asbestos mines at two locations, the air borne fiber levels were within permissible limits. The average fiber levels in milling units were between 45 fibers/ml -244 fibers/ml.
The burden of asbestos-related diseases is still rising, even in countries that banned the use of asbestos in the early 1990s. Because of the long latency periods attached to the asbestos related diseases, stopping the use of asbestos now will result in a decrease in the number of asbestos-related deaths only after a number of decades. There is no safe use of asbestos and no safe limits set by WHO, ILO (International labour organization).
Park’s Textbook of Preventive and Social Medicine, 22nd Edition, Page No 752.
· Shortness of breath, wheezing, or hoarseness.
· Persistence of cough gets worse over time.
· Blood in sputum.
· Pain or tightening in the chest.
· Difficulty swallowing.
· Swelling of the neck or face.
· Loss of appetite.
· Weight loss.
· Fatigue and anemia.
The disease is progressive even after removal of the worker from the contact. In advanced cases there may be clubbing of finger nails, distress, and cyanosis.