Although asbestiform amphiboles only contributed less than 6% of industrial asbestos worldwide, they have proved more toxic as mineral pathogens than the more commonly mined asbestiform serpentine (chrysotile or white asbestos). Most amphibole asbestos was mined as crocidolite (blue) and amosite (brown) from Precambrian banded ironstones in South Africa and, to a lesser extent, Western Australia. Blue and brown asbestos not only can induce asbestosis at lower concentrations than white asbestos, but they are highly carcinogenic. Early awareness of asbestos-related diseases in producer countries did not translate into preventative action before hundreds of thousands of individuals had been exposed to high fibre levels. The situation was most acute in South Africa where the occupational health status of black Africans in particular was badly neglected. In at least one mine, children were used to trample shipping bags filled with amosite, and in doing so received what is thought to have been the highest ever inhalation dose of amphibole asbestos. South Africa now has the highest rate of asbestos-induced mesothelioma in the world, with this invariably fatal cancer responsible for over 9% of deaths in a study conducted in a former Cape crocidolite mining town.

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