Background asbestos fiber levels in autopsy lungs: Implications for forensic disease attribution in the post-ban era

Asbestos exposure is a well-established cause of malignant mesothelioma and other respiratory diseases, and quantifying inorganic fiber lung burden is crucial in forensic and medico-legal contexts for attributing disease causality. However, data on background asbestos exposure and chronological trends in the general population remain limited. This study analyzed autopsy lung tissue samples from 81 individuals (38 males, 43 females) from Northern Italy who died between 2001 and 2024, all with no documented history of occupational or environmental asbestos exposure. Inorganic fibers, including asbestos and nonasbestos types, were counted and characterized using scanning electron microscopy with energy dispersive spectroscopy, and concentrations were normalized per gram of dry lung tissue. Asbestos fibers were detected in 22.2% of cases, predominantly tremolite/actinolite, with higher concentrations observed in males. Ferruginous bodies were present in 17.3% of samples. Notably, asbestos lung content demonstrated a significant decline over time: only 9.5% of individuals born after 1946 had detectable asbestos fibers, compared to 35.9% of those born before 1946 (p < 0.05). Nonasbestos fibers, mainly talc, other phyllosilicates, and titanium dioxide, were also identified but did not show clear chronological trends. These findings indicate a marked decrease in asbestos lung burden in the general population, likely reflecting the effectiveness of asbestos bans. Current background levels are substantially lower than historical thresholds used for disease attribution, highlighting the need to revise reference values to ensure accurate causal attribution of asbestos-related diseases in forensic practice.