Biodurability/retention of Libby amphiboles in a case of mesothelioma

Mesothelioma is considered a signal tumor for exposure to asbestos (fibrous materials) and can occur decades after first exposure. The present case study reports on tissue burden of fibrous dust in a person who used a vermiculite material (Zonolite) as an attic insulator some 50 years prior to her death. The exposure occurred in two construction/renovation projects in her private residencies. She potentially had exposures to wall board/joint compounds during renovations. She additionally was reported to occasionally be involved in occupational activity, including drilling holes in presumed asbestos-containing electrical boxes. The tissue burden analysis revealed the presence of noncommercial amphibole asbestos fibers and consistent presence in the lung and lymph samples of Libby amphibole fibers. The findings of Libby amphibole fibers in human tissue can be attributed to exposure to Libby vermiculite. This study illustrates that analytical transmission electron microscopy can distinguish these structures from "asbestos" fibers. Further, the findings indicate that a population of these structures is biodurable and retained in the tissue years after first/last exposure.