Detection and Characterisation of Airborne Carcinogenic Erionite Fibres in New Zealand Roadside Environments Using a Novel Integrated Methodology
Geogenic airborne dust is a common phenomenon in both urban construction zones and rural roadside environments, particularly where sediment layers are exposed and disturbed. In regions with volcaniclastic geology, such dust may contain naturally occurring carcinogenic minerals, including fibrous asbestos and erionite. Erionite, a fibrous zeolite, is of particular concern as it has been classified as a Group 1 carcinogen and exposure to erionite is strongly linked to the development of malignant mesothelioma, one of the most aggressive cancers known. Although the geological occurrence of erionite has been reported worldwide, including in populated areas of New Zealand, its detection in the air remains extremely challenging due to methodological limitations and its similarity to other fibrous zeolites. These challenges have resulted in critical gaps in understanding the aerosolisation pathways, fibre size characteristics, and potential public exposure risks. This thesis investigates whether erionite fibres can be dispersed into ambient air from geological deposits, whether transported fibres occur in respirable and hazardous size ranges, and whether individual fibres from mixed particulate samples can be reliably identified as erionite. A novel, low-cost screening method was developed using passive sampling for dust deposited on vegetation in roadside environments, combined with a multi-technique analytical approach: commencing with scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) for fibre counting and chemical-morphological assessment, and then transmission electron microscopy with selected area electron diffraction (TEM-SAED) and MicroED for crystallographic confirmation. The analytical pipeline was validated using erionite-K bulk reference samples confirmed by X-ray diffraction (XRD). Field applications were conducted in three disturbed environments with known zeolite deposits in New Zealand: two quarry sites, a roadside volcanic erionite outcrop, and a broader area with exposed roadside outcrops. The results demonstrated that by using the novel integrated approach developed and refined in this project, erionite and other fibrous zeolites can be detected in respirable sizes in surface dust in roadside environments. The findings provide new evidence that respirable erionite fibres can be released under real-world environmental conditions and support the need for improved airborne fibre monitoring in volcanic and volcaniclastic regions.
Respirable mineral fibre, Surface dust, Erionite, Mordenite, Mineral fibre air-dispersion, SEM-EDX, TEM-SAED, Exposure risk
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