Toxic Zeolite Minerals and Implications for Ground Engineering and Earthworks: Case Study from New Zealand

Summary The generation of toxic mineral dust from both tunneling and surface groundworks has emerged globally as an important occupational and non-occupational health hazard in recent years. A particular focus has been on health issues relating to workers who have been exposed to respirable crystalline silica (RCS) during long-term occupational activities, developing irreversible and progressive pulmonary fibrosis. In addition to RCS, a different suite of naturally occurring toxic minerals are mineral fibers formed of erionite, a zeolite mineral. Erionite is a naturally occurring “asbestiform” mineral that belongs to a group of silicates called zeolites. It is listed by the International Agency for Research on Cancer (part of the World Health Organization) as a Group 1 known carcinogen. Studies have demonstrated that erionite is more carcinogenic than asbestos, with similar effects to asbestos, such as malignant mesothelioma (MM). Erionite is known to occur in the Auckland region of New Zealand, at surface exposures, and so disturbance of the mineral during earthworks and ground engineering projects is a concern. Auckland is New Zealand’s fastest growing region, with large infrastructure projects that often include, tunnelling as well as excavations on “greenfield” sites. Latest results, possible exposure pathways and mitigations, are reported here.