Metsovo lung was an epidemic of lung disease resulting from domestic exposure to asbestos in the village of Metsovo in northwest Greece. Most of the inhabitants had previously been exposed to a whitewash derived from local soils containing tremolite asbestos. This caused an epidemic of malignant mesothelioma that reached an incidence 300 times that expected in populations not exposed to asbestos. This was accompanied by pleural calcifications in almost half the adult population. Both conditions have declined significantly since the whitewash ceased to be used after 1985.
Locally high rate of PCs
In the early 1980s when the Medical School of Ioannina was established, a group of pneumonologists headed by S.H. Constantopoulos started encountering, almost on a daily basis, X-ray images with extensive PCs in inhabitants of Metsovo. The researchers were told that this was very common to Metsovites and was the result of old tuberculous pleurisy. However, since the picture was not even remotely similar to calcified pleurisy from previous tuberculosis, they began to investigate the precise frequency of PCs, whether their abnormal incidence was in fact confined to Metsovites, and their true cause. In a field study in Metsovo and other areas around Ioannina, it was confirmed that PCs were very common among Metsovites, around 50% of adult population, increasing to more than 80% in those above 70; and that they were seen only in Metsovo and three neighbouring villages.
Relation to asbestos
The relation to asbestos was identified when, a few months later, two consecutive patients appeared with massive pleural effusions that proved to be malignant mesothelioma. These were only the first of a series of mesotheliomas; seven in five years. This rate is roughly 300-times that expected in a non-asbestos exposed community. The combination of PCs and MM can only be attributed to asbestos exposure. Transbronchial lung biopsies from Metsovites with extensive PCs were then obtained and sent to Mount Sinai Hospital in New York. Their analysis revealed long thin tremolite asbestos fibers in most biopsies in spite of their minuscule size.
Projected course
Having found the most likely cause of PCs and mesotheliomas in Metsovo and the temporal course of its use, from 1940-1950 when it was used by all households until 1980-1985 when it was abandoned, it was possible to project the future course of this epidemic. First, other sources of asbestos exposure, after the abandonment of louto, had to be excluded. Two clinical means of measuring exposure were used for this purpose. Both had been positive in practically all exposed Metsovites during the peak of louto use: chest computed tomography and bronchoalveolar lavage. A study of Metsovites between the ages of 30 and 50 confirmed that louto was the only source of asbestos exposure in Metsovo, as none of the subjects examined had PCs or asbestos fibers. Finally, after thirty years of research it was possible to examine the dynamics of the frequency of PCs among Metsovites between 1980-2010. As expected, their frequency was found to be decreasing and the age when PCs are first seen was increasing, In regard to mesothelioma, after the first study in the 1980s, two studies have shown that the incidence of mesothelioma is also dropping. However, the end of this epidemic cannot be predicted safely. Mesotheliomas appear usually 30–50 years after exposure but this can be prolonged, very rarely, to 70 years. Thus, since the use of louto stopped between 1980-1985, a decreasing incidence of mesothelioma may be expected until 2020-2030 and possibly 2040.
