Fibrous Zeolites and Pulmonary Fibroblasts: Toxicological Impact and EPR-Based Insights into Cellular Alterations

This study investigates the potential cytotoxicity of the carcinogenic erionite and other fibrous zeolites, including mordenite, ferrierite and scolecite. Their interactions with human lung fibroblast cells (MRC-5) were evaluated using biological assays combined with Electron Paramagnetic Resonance (EPR) spectroscopy. All fibrous zeolites were found to interact with lung fibroblasts, leading to increased intracellular ROS levels and alterations in the lysosomal compartment after 24 hours of exposure. EPR measurements after CAT16 incubation provided further insight into cellular membrane interaction dynamics, revealing notable differences in spectral intensity and hyperfine coupling constants, which suggest distinct interaction mechanisms among the fibers. Erionite showed the highest radical solubilization, implying potential cytotoxic effects. Prolonged exposure to mordenite and ferrierite also significantly reduced cell viability, at levels comparable to erionite. These findings highlight key factors involved in early inflammatory responses and their potential contribution to the development of long-term chronic diseases and cancer. The biological effects of fibrous zeolites are controlled by a multifactorial interplay between morphology, surface area, chemical composition, and biopersistence, which together determine the extent of membrane interaction, oxidative stress generation, and intracellular processing, ultimately governing cytotoxicity and potential carcinogenicity. This study therefore provides an initial step toward understanding the biological mechanisms underlying the toxicity and carcinogenic potential of fibrous zeolites, improving awareness of their potential human health risks.