Environmental ‘Low Dose’ Mesotheliomas and Their Relationship to Domestic Exposures-Preliminary Report

Abstract

Crocidolite is a fibrous mineral with unusual crystallography in that the fiber width varies according to geographical origin. The fibers from the mining areas of Western Australia and the Cape Province, in South Africa are ‘thin’ compared to those from Bolivian and some other mines. Regardless, the mineral is a well known causative agent for mesothelioma. The literature contains many reports of the disease occurring as a consequence of so called environmental exposures due to what some believe to be ‘low’ dose, ambient exposure. However, closer examination of these exposure conditions generally reveals an unrecognized (or simply ignored) strong domestic (para-occupational) exposure component. Oftentimes, the importance of such domestic exposures is not considered since they too are thought to be too low to contribute to risk. We have, for the first time, applied state of the art measurement methods to evaluate domestic (shake out) conditions created by workers in a historical unregulated crocidolite-cement based operating plant in Bolivia. Our results show that exposures can reach levels more usually associated with historic occupational exposures. The reason for studying the exposures in such a plant is that epidemiological studies have shown that ‘thin’ crocidolite fibers are associated with a high mesothelioma risk while exposure to the ‘thick’ Bolivian fibers are associated with a much lessened mesothelioma risk.