Asbestos lung fibre concentrations in South African chrysotile mine workers

Mesothelioma has not been found in South African chrysotile miners and mill ers despite decades of producing about 100 000 tons of the mineral per year . One possible explanation for the scarcity or absence of the cancer may be a relative lack of contaminating fibrous tremolite, an amphibole that vari ably occurs with chrysotile ores. The fibre content in the lungs of nine fo rmer chrysotile mine workers was ascertained by transmission electron micro scopy. Despite fairly long service in most cases (median 9.5 yr; range 32-4 yr) the concentrations of chrysotile fibres were relatively low: only two cases exceeded 1.14 million fibres/g dried lung. Tremolite fibre levels wer e even lower: less than 1 million fibres/g dried lung in all but one case. Tremolite fibre concentrations exceeded those of chrysotile in only two cas es. These results support the contention that South African chrysotile is n ot heavily contaminated by tremolite. (C) 2001 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.