Naturally occurring asbestos in eastern Australia: a review of geological occurrence, disturbance and mesothelioma risk

To estimate the importance of low dose exposure to asbestos on the risk of mesothelioma. A review of the literature. There is no evidence of a threshold level below which there is no risk of mesothelioma. Low level exposure more often than not contains peak concentrations which can be very high for short periods. There might exist a background level of mesothelioma occurring in the absence of exposure ot asbestos, but there is no proof of this and this "natural level" is probably much lower than the 1-2/million/year which has been often cited.

The 575 inhabitants of the remote Anatolian village of Karain suffered 11 deaths from pleural mesothelioma in 1975/76 and there were five cases of fibrosing pleurisy. In the previous five years there had been 25 cases of mesothelioma. Calcified pleural plaques were common on survey radiography. Asbestos does not occur in the local soil or rock, nor is it handled in the village, but a few fibres were found in the water. Fibres were also found in the pleural tissue of two of five cases examined. Inhabitants of the neighbouring villages are free of mesothelioma.