Mesotheliomas--asbestos exposure and lung burden.

The assessment of asbestos fibres in the lungs at post mortem in groups of mesotheliomas, groups occupationally exposed to asbestos, and controls has shown that all these groups contain significant levels of asbestos as a lung burden. The amounts in each group are dependent on the degree of past exposure, being highest in those cases with a known or extrapolated occupational exposure, less in those cases with recorded neighbourhood or environmental exposure, and less again in those cases with no evidence of exposure to asbestos and in controls. Relative risk estimates and the use of models developed for occupational situations do not provide good estimates of the relevance of environmental fibres in producing mesotheliomas in the general population. This may be the result of differences between the groups in their time periods of exposure and long-term elimination of asbestos from the lungs. The number of mesotheliomas that might be due to low-level environmental exposure to asbestos cannot be determined from lung contents alone, but an assessment based on detailed occupational histories from the Australian Mesothelioma Surveillance Program show that the problem is not one of great importance when compared with other public health issues.