ASBESTOS LUNG BURDEN DETERMINATION IN AN URBAN POPULATION FROM MILAN, ITALY. ANALYSIS OF A NECROSCOPIC SERIES FROM 2009 TO 2011.

The present study analyzed the asbestos lung burden from a necroscopic series of the Milan general population. The study was performed on 55 cases free from asbestos-related disease undergone a judicial autopsy at the Forensic Institute of Forensic Medicine of Milan in the period running from 2009 to 2011. For each study case multiple lung samples were digested and vacuum-filtered on 0.2 μm pore size polycarbonate membranes and then were analyzed by both traditional Light Microscopy (for counting of morphologically typical Asbestos Bodies) and EDXA-Scanning Electron Microscopy (for counting of all asbestos fibers). The SEM-analysis also extended to the count of inorganic fibers other than asbestos. The Asbestos Bodies prevalence in the series was 14.5% with the positive cases having an AB count ranging from 10 to 110 AB/g dry. No Asbestos Bodies were found in the subjects younger than 30 years. Asbestos fibers were SEM-detected in 63.6% of the study cases, with a higher detection frequency for amphiboles than for chrysotile (58.2% versus 20%). An asbestos content lower than the SEM analytical sensibility was found in 80% of the subjects younger than 30 years. Commercial Amphiboles were detected as frequently as NonCommercial Amphiboles. NonCommercial amphiboles were mainly represented by tremolite fibers. The estimated median value was 110,000 ff/g dry (IQ range 62,250-275,000 ff/g dry) for all the asbestos fibers, 91,600 ff/g dry (IQ range 60,000-180,000 ff/g dry) for the amphibole fibers and 51,600 ff/g dry (IQ range 46,600-65,000 ff/g dry) for the chrysotile fibers. The maximum estimated burden for all asbestos fibers was 2,000,000 ff/g dry. Thirteen cases showed an amphibole burden higher than the Helsinki cut offs for occupational exposure: three cases showed a total amphibole burden higher than 1,000,000 ff/g, while other 10 cases showed an amphibole burden for fibers longer than 5 μm higher than the 100,000 ff/g dry. A comparison was performed between our results and the results coming from two distinct occupational-exposed populations examined by the same SEM laboratory. The maximum measured asbestos burden in our population was lower than the minimum measured asbestos burden among asbestos-textile workers, jute recycling workers and asbestos-cement workers. Just one asbestos-cement worker and 4 silk/cotton-textile workers showed asbestos lung concentrations overlapping our experimental results. A positive linear relationship was observed between asbestos lung burden and age at death. Sex, residential district, birthplace and smoking habit did not significantly influence the median asbestos lung burden. The mean dimension for the detected asbestos fibers was 4.19 x 0.19 μm with a 20.6 mean aspect ratio. Chrysotile fibers (mean dimension 2.74 x 0.09 μm) were significantly shorter and thinner than amphibole fibers, the NonCommercial Amphibole fibers (mean dimension 5.65 x 0.47 μm) being also significantly thicker than the Commercial Amphibole fibers (mean dimension 4.86 x 0.17 μm). Asbestos fibers traditionally supposed to be fibrogenic and carcinogenic in humans were very infrequently detected. The median talc burden was very similar to the median asbestos lung burden and the global non-asbestos fibers lung burden well outnumbered the asbestos fibers burden. Also for inorganic fibers other than asbestos a positive linear relationship with age at death was observed.