2. Chrysotile and Health
2.1 Risks of prolonged and elevated exposures
For many years, dust concentration of up to 200 f/cc could be found in certain asbestos industry sectors, particularly those involving the use of friable (spray-on) applications. In many workplace environments, dust clouds were so thick that it was difficult for workers to see each other even at short distances. Unfortunately, this has resulted in a legacy of asbestos-related disease particularly amongst workers in the shipbuilding and construction trades.
Three types of respiratory disease have been identified with exposure to asbestos: asbestosis, a scarring of the lung tissue which can impede normal respiratory function; lung cancer, a malignant, invasive growth or tumour in the lung; and mesothelioma, a rare form of malignant tumour of the lining of the chest or abdominal cavities. The latency period associated with these diseases can range from 10 to 40 years from first exposure. The risk of lung cancer is significantly increased amongst asbestos workers who smoke tobacco. All types of asbestos fibres were classified as Class I known human carcinogens by the International Agency on Research for Cancer in 1977.
2.2 Health risks are associated with inhalation not ingestion
Over the years, numerous animal feeding experiments and epidemiological studies have been conducted to determine whether high concentrations of ingested asbestos pose a health hazard. The majority of these studies found no excess cancers, despite doses up to 100,000 times higher than levels found in heavily contaminated drinking water. Similarly, several long-term epidemiological studies have concluded that there is no solid evidence that asbestos in drinking has any adverse effects on humans, even under conditions of heavy exposure. Therefore there is broad scientific consensus, including experts from the World Health Organization (WHO), that chrysotile asbestos does not present a detectable risk of cancer by the route of ingestion.
2.3 Health risks are occupational not environmental
Chrysotile asbestos is a naturally occurring mineral which has been present in the air and water around the world long before it was mined and used commercially. On average, humans inhale thousands and ingest millions of asbestos fibres each and every day without any detrimental effects. The potential health risks associated with chrysotile asbestos are occupational and not environmental in nature. As a result, the WHO concluded that the general population is not at detectable risk at the low levels of asbestos exposure typically found in the general environment (e.g. 0.0001 to 0.001 fibres/ml).
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