Analysis of latency time and its determinants in asbestos related malignant mesothelioma cases of the Italian register

Italy was an important producer of raw asbestos until 1992 (when it was banned) and it is now experiencing severe public health consequences due to large-scale industrial use of asbestos in shipbuilding and repair, asbestos-cement production, railways, buildings, chemicals and many other industrial sectors. Latency of malignant mesothelioma generally shows a large variability and the relationship with the modality of asbestos exposure is still not fully clarified. We present an analysis of latency period among the case list collected by the Italian mesothelioma register (ReNaM) in the period of diagnosis 1993-2001 (2544 malignant mesothelioma (MM) cases with asbestos exposure history). Exposure is assessed retrospectively by interview. Statistical univariate analyses were performed to estimate median and variability measures of latency time by anatomical site, gender and diagnosis period. The role of diagnostic confidence level, the morphology of the tumour and the modalities of asbestos exposure were verified in a regression multivariate model. We found a median latency period of 44.6 years increasing in recent years with a linear trend. Anatomical site, gender and morphology were not relevant for MM latency time whereas a shorter latency period was documented among occupationally exposed subjects (43 years) with respect to environmentally and household exposed ones (48 years).