2. Chrysotile and Health
2.4 Health risks of different types asbestos fibre
There is a clear international scientific consensus that chrysotile is less hazardous than the amphibole varieties of asbestos. Not only is chrysotile a less dusty material because of its physical properties, it also has a tendency to break down and dissolve in body fluid and thus is more easily cleared from the lungs by natural defense mechanisms. Amphibole forms, on the other hand are more dusty materials as well as more durable and persist in the lung once inhaled. The increased potency of amphibole forms of asbestos compared to chrysotile is corroborated by both animal and human studies.
2.5 Product Risks
Today, only chrysotile asbestos is used. In addition, industry now only manufactures and markets high-density non-friable products in which the chrysotile fibre is encapsulated in a matrix of either cement or resin. These modern products include chrysotile-cement, building materials, friction products, gaskets and certain plastics. According to a Group of Experts meeting convened by the International Programme on Chemical Safety (IPCS), in December 1988, these products do not present risks of any significance to public health or the environment. However, it was recommended that the use of low-density friable insulation material that can crumble under hand pressure be banned because of the risks to workers who may handle them. Friable asbestos insulation products have been banned in most countries since the mid-70's.
2.6 No detectable health risk at low levels of occupational exposure
There is ample human and animal evidence that at high and prolonged levels of exposure, chrysotile asbestos can cause disease. However, the question that scientists are now evaluating is whether or not there exists a threshold level of exposure below which there is no increased risk of disease. In the case of chrysotile asbestos there is mounting human evidence pointing to the existence of a practical occupational threshold. Although additional research will be required to more accurately define these threshold levels, there is a broad consensus that at a 1 f/cc exposure limit, workers (smokers and non-smokers alike) will not be at any detectable increased risk of asbestos-related disease.