GEOLOGICAL OCCURRENCE, MORPHOLOGICAL CHARACTERISATION, AND TOXICOLOGICAL EVALUATION OF FIBROUS ZEOLITES IN NEW ZEALAND

Volcanic activity in New Zealand has given rise to a wide variety of minerals, one such group of minerals are zeolites, which primarily form though diagenesis or hydrothermal alteration of volcanic rocks. While there are over 40 naturally occurring zeolites worldwide, erionite, a is a rare fibrous zeolite mineral, associated with malignant mesothelioma (MM). A significant epidemic was discovered in the Cappadocia region of Turkey in the 1970s, due to erionite exposure. While undisturbed erionite fibres are not considered harmful to human health, the International Agency for Research on Cancer (IARC) has designated erionite as a Group 1 carcinogen due to its hazardous potential when disturbed or inhaled. Various analytical techniques are being utilised to detect and characterise erionite in New Zealand, including: Scanning Electron Microscopy, X-Ray Powder Diffraction, and Transmission Electron Microscopy. These same methods have shown that mordenite, a more common fibrous zeolite, has very similar characteristics to erionite. In-vitro toxicity tests have also been conducted on two of the erionite samples (Gawler Downs and Kaipara) with results indicating that NZ erionite exhibits an acute toxic potential, especially in relation to non-carcinogenic fibres such as wollastonite. Indeed, over a 7-day period, Gawler Downs erionite led to 90% cell death, and Kaipara led to 80% cell death of THP-1 macrophages during a cytotoxicity test assessed by the MTT assay. In-vitro toxicity tests on mordenite are currently underway. Due to the potential adverse health effects linked to erionite exposure, this research aims to develop an understanding of fibrous zeolite occurrences in New Zealand, to mitigate any potential environmental hazards.