Learn about Local Deposits of Fibrous Minerals

In many areas of the world, asbestos fibers occur in the soil, as remnants of broken down rocks. Farmers working with the soil are exposed to the fibers, and in many places the locally occurring asbestos has been used for white-washing of houses, construction of fireplaces or sauna stones (23-25). As a result there are areas of the world where pleural plaques are endemic. Such "endemic pleural plaques" were first described from Finland and since then many other areas have been reported.

The older age groups can show calcified plaques in 50 per cent or more radiographically and even more at autopsy (up to 100 percent in persons above age 50) though usually the incidence is more modest. Where the fibers occur in the soil, farmers are exposed and then the plaques are more common among males. Where the mineral fibers are used for white-washing of houses, the women also have a high incidence of plaques.

One of the best described countries is Turkey, where there are not only villages with exposure to asbestos but also some where a non-asbestos fibrous mineral has been found to cause endemic pleural changes. This fiber is erionite, a fibrous zeolite, which was formed during volcanic activity and occurs locally in some few villages, the best known of which is called Karain. The erionite occurs in roads, fields, and building stones. Apart from the pleural changes, these villages also have an extremely high incidence of malignant mesothelioma. In fact, this dreadful disease is the main cause of death there.

Endemic plaques are of interest also in other countries, since many persons born in these places and living there in their childhood and youth now have moved to other places, taking with them not only the plaques but also the risk of mesothelioma and lung cancer.