A recent WHO report states that asbestos is one of the most important carcinogens, causing about half of all occupational cancer deaths in the world.

Asbestos is one of the most important occupational carcinogens, causing about half of the deaths from occupational cancer. Asbestos is a unique type of mineral that can be pulled apart into flexible fibers. When microscopic asbestos fibers are inhaled or ingested, the body may never be able to dissolve or expel them. Over the span of many years, the fibers can cause genetic changes that can lead to asbestos cancer. Most cases of asbestos cancer trace back to recurring occupational exposure, though secondhand and environmental exposure can cause cancer as well.

The main forms of asbestos are chrysotile (white asbestos) and crocidolite (blue asbestos). Other forms include amosite, anthophylite, tremolite and actinolite, a WHO report said. 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.

Currently, about 125 million people in the world are exposed to asbestos at the workplace. 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 fibres substantially increases the risk for lung cancer – and the heavier the smoking, the greater the risk.

Many fibre substitutes for chrysotile asbestos assessed by WHO pose a relatively low hazard to human health, though, the carcinogenic hazard of some fibre substitutes was found to be high. However, there are many non-fibre low hazard materials that can substitute for chrysotile asbestos in various uses, such as conventional building materials.