Erionite is a naturally occurring zeolite, a crystalline material characterized by a framework of silicon/aluminium-centred tetrahedra, joined together by means of the oxygen atoms at the vertices. The open framework contains channels and cavities (micropores) that accommodate varying amounts of exchangeable H2O molecules and extra-framework cations, such as sodium, calcium, magnesium, potassium.
Erionite is found in nature in the form of bundles of very thin fibres (Figure 1), the appearance of which resembles a wad of wool (“erion” in Greek means wool) and, much more rarely, as individual needle-like fibres. Erionite has caused exceptional cancer (malignant mesothelioma) morbidity in some areas of Cappadocia (Turkey) and is now classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen. In fact, erionite’s high biopersistence—its ability to remain in the body without breaking down—combined with its unique ion-exchange properties, makes it one of the major natural hazards.A collaboration between Elettra, the Universities of Modena and Reggio Emilia, Genova and Parma, and the Italian National Research Council has made significant strides in understanding the toxicity mechanisms of erionite. In a groundbreaking study, the team employed cutting-edge synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-X-ray absorption spectroscopy to investigate how erionite-Na interacts with human macrophages, the immune cells responsible for engulfing and digesting foreign particles. |
The study revealed that when macrophages engulf erionite fibres, there is a significant disruption in the balance of intracellular calcium and sodium ions. This disruption is crucial as it triggers harmful cellular responses, potentially leading to cancer-promoting adverse effects.Surprisingly, the anticipated major role of erionite’s ion-exchange capacity in toxicity was found to be less significant than previously thought. Instead, the internalization of iron-rich particles associated with erionite fibres and the subsequent cellular stress play a more critical role. These findings help clarify why erionite is much more potent in causing malignant mesothelioma than other mineral fibres like asbestos. The study employed soft X-ray microscopy combined with low energy sub-micro-XRF mapping at the TwinMic beamline of Elettra Sincrotrone Trieste complemented by measurements taken at the ID21 beamline of ESRF Synchrotron in Grenoble, France.
Read more on Elettra website
Image: High resolution TEM image of an erionite bundle
Credit: E. Mugnaioli