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 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.
Repeated or prolonged inhalation of asbestos fibers may cause asbestosis (fibrosis of the lungs), pleural plaques, thickening and pleural effusion. Individuals who have been exposed (or suspect they have been exposed) to asbestos fibers on the job, through the environment, or at home via a family contact should consult their doctor whether or not they experience any symptoms. The symptoms of asbestos-related diseases may be apparent after many decades, such as;
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.
There are six types of asbestos minerals (chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite). All commercial forms of asbestos are carcinogenic.
Exposure to asbestos mostly occurs through inhalation of fibers primarily from contaminated air in the working environment, or from ambient air in the vicinity of point sources or indoor air in housing and buildings containing friable asbestos materials. Friable asbestos materials continue to give rise to exposure during maintenance, alteration, removal and demolition. Exposure can also occur as a consequence of natural disasters causing damage to buildings.
Asbestos can enter both in ground and surface water from natural and anthropogenic (changes in nature by people) sources. Soil can also contain asbestos through natural and anthropogenic (disposal of asbestos containing wastes in landfill) sources.
Occupational exposure -The highest levels of exposure occur during repackaging of asbestos containers, mixing with other raw materials and dry cutting of asbestos-containing products with abrasive tools. Exposure can also occur during installation and use of asbestos-containing products and maintenance of vehicles.
Exposure of the general population- Inhalation and ingestion are the primary routes of exposure to asbestos. Inhalation of asbestos fibers from outdoor air and to a lesser degree in indoor air is the primary route of exposure for the non- smoking general population (white collar workers within the asbestos industry, individuals living in the vicinity of asbestos mines). Exposure may also occur via ingestion of drinking water which has been contaminated with the asbestos.
Families of asbestos workers may be exposed via contact with fibers carried home on hair or on clothing. Asbestos related diseases have been reported in wives and children of asbestos workers, as a result of domestic exposure.
Construction activities and inadvertent exposure of the wider population from degradation of building materials (e.g. broken corrugated asbestos roof tiles) and inappropriate disposal of building waste also expose to general population to asbestos.
Elevated concentrations of asbestos fibers in ambient air were observed at busy traffic intersections from friction products in vehicles.
Factors affecting the risk of developing asbestos–related diseases-
A thorough physical examination is recommended with the following tests-
No specific therapy is recommended for asbestos related diseases.
Smoking cessation, withdrawal from further exposure is advised.
Treatment of asbestos –related disease includes vaccination against influenza and pneumococcal pneumonia, antimicrobial therapy for respiratory infections and the use of oxygen if necessary.
Surveillance for lung cancer and mesothelioma should be done.
A multidisciplinary approach focused on supportive care; multimodality treatment including surgery, radiotherapy, and chemotherapy may be considered in cancer cases.
The spectrum of asbestos-related diseases includes the following:
Workers can protect themselves in work place by taking various measures;
Preventive measures at work place:
WHO has recommended following public health action;