[The erosion of asbestos cement roofs: an important source of environmental pollution]

A microscopic investigation on samples of asbestos cement roofs weathered from 2 months to 15 years or more was carried out. Surface alterations begin as early as 2 months, are well visible after a few years and become very severe after 5-10 years. The deterioration of the cement structure, due mainly to the chemical attack of the acid rains produces a release of fibres that is more evident with increasing duration of the exposure. The surface of the "old" roofs must be considered as important source of environmental pollution, that increases the total carcinogenic potential of the polluted atmosphere in a non-negligible way, considering also the enormous extension of the surfaces. Instead of replacing the roofs, adequate primers and sealants can be applied after careful preparatory cleaning: gross contamination of water and/or surrounding areas must be avoided by appropriate work procedures. The deteriorated materials containing amphiboles must be considered with priority.