Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line

Asbestos fibres can be transformed into potentially non-hazardous silicates by high-temperature treatmentvia complete solid-state transformation.A549 cells were exposed to standard concentrations of raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200C (Cry_1200 and KRY-AS, respectively),raw commercial grey cement (GC). Cell growth rate and viability (MTT test) were detected in vitro. RCA and KRY-AS subjected to comprehensive microstructural study by electron microscopy were furtherin vitro assayed to compare their cytotoxic potential by morphostructural studies, proliferation index (Ki-67 antigen), apoptosis induction (AO/EB staining) assays and detection of intracellular reactive oxygen species (ROS) with the fluorescent DCFA dye. More severe cytotoxic damage was induced by RCA than by KRY-AS after each incubation period. Exposure to KRY-AS and GC resulted in comparable cell growth rates and cytotoxic effects. Cells incubated with RCA showed greater apoptotic induction and ROS production and a lower cell proliferation index than those exposed to KRY-AS. Chrysotile asbestos and RCA subjected to heat treatment underwent complete microstructure transformation. The final productof heat treatment of cement asbestos, KRY-AS, was considerably more inert and had lower cytotoxic potential than the original asbestos material in all in vitro tests