What lies beneath: is this the new asbestos?

Erionite is a naturally occurring mineral which has been found in rocks around the Auckland region. You may never have heard of it, but international studies are linking exposure to this pale crystal to cases of malignant mesothelioma, a form of lung cancer more commonly associated with asbestos.

We will be investigating the risk this potentially toxic mineral poses to New Zealand in a research project which has just been awarded $7.6 million over four years from the Ministry of Business, Employment and Innovation (MBIE) Endeavour Fund for 2020.

We will be working with geologists, environmental scientists, medical specialists, engineers, policy-makers, industrial experts, social scientists and end-users from the wider community to quantify the risks posed by erionite and enable the development and implementation of sound risk assessment strategies and safe management practices where necessary.

The connection between erionite and cancer was first made in Anatolia, Turkey in the 1980s. Residents of Tuzkoy, Karaiun and Sarahidir presented with unusually high rates of lung disease. Like other cancers, malignant mesothelioma appeared to strike at random. Some households were catastrophically affected while others were spared, and not all members in a household were equally affected.

Initially misdiagnosed as tuberculosis, and later blamed on exposure to asbestos, it was only latterly that the cancer was linked to the rocks that houses in these villages were largely built from. These local rocks were soft, easily releasing dust rich in erionite, the mineral which was ultimately, causatively linked to about 50 percent of deaths among residents.

It had been assumed the risk presented by erionite was limited to this tragic, but ultimately unique, case study. However, recent concerns have emerged about the relationship between erionite and mesothelioma in other countries including the US and Italy. By 2011, erionite had been discovered in 12 US states, found to be several hundred times more carcinogenic than asbestos and was identified by the US Centres of Disease Control and Prevention as an emerging public health risk.

When erionite remains buried below surface it does not present a risk to people. However, if disturbed, erionite can become airborne and inhaled into the lungs. In North Dakota, for example, rocks containing erionite were inadvertently used in rural roading. Subsequently, high concentrations of erionite fibres were found in local vehicles including school buses, likely transferred by students who had waited in roadside bus stops.

Establishing the link between erionite exposure and development of associated lung disease remains difficult. It often takes several decades (estimates range from 20 to 60 years) for malignant mesothelioma to develop after initial exposure. Thus it is unsurprising that a significant mesothelioma cluster has not yet been detected in North Dakota given the low population density and that insufficient time has likely lapsed since the road surfacing was undertaken. This lag makes it challenging to ascertain relevant exposure information to determine case histories and link cause and effect. Further, the only reliable way to distinguish between asbestos and erionite exposure as the underlying cause of disease is by lung biopsy, which is not routinely done. As with asbestos exposure, some people appear more susceptible to developing the disease following exposure than others, and we have yet to understand why.

In Auckland, erionite was first accurately identified in the 1970s when we were still unaware of the health risks. Erionite is relatively rare and formed in volcanic rock. It can be dissolved and re-deposited in sedimentary rock where it can accumulate in locally high concentrations. Erionite has since been found in Waitematā Group sedimentary rocks and Waitakere Group volcanic rocks. These types of rocks are located throughout Auckland including under parts of the CBD, extending into patches north of the city where they can be found closer to the surface. However, the precise location, distribution, proximity to the surface, and concentration of erionite within this rock type is not yet known.

We don’t know enough about the risks erionite presents as it is an emerging hazard. The International Association for Engineering Geology (IAEG) Commission on Naturally Occurring Asbestos has only recently established a working group on erionite and New Zealand scientists are part of this advisory team. Unlike asbestos, there are no guidelines yet about how much erionite we can be exposed to, to help us mitigate the risks. The delay between cause and effect, combined with difficulties measuring environmental exposure to erionite, and differences in the composition and toxicity of erionite, make it very difficult to establish how much erionite people can be exposed to safely.

The public and occupational health impact of erionite in New Zealand has not been studied. New Zealand has a relatively high rate of malignant mesothelioma compared to other high-income countries. We have previously assumed this is due to asbestos exposure. Given we now know erionite is in Auckland, more research is needed to ensure it isn’t contributing to the incidence rate of malignant mesothelioma.

Evidence suggests local populations who live in areas where there are natural outcrops of rock containing erionite near the surface may be at increased risk from this cancer. However, this is most likely in dry, windy climates. Since notable clusters of malignant mesothelioma have not been observed in Auckland, there is good reason not to be overly concerned about the risk from natural, undisturbed outcrops at this point.

As Auckland enters a new phase of earthwork and construction activity, it is important to ensure erionite deposits below surface are not inadvertently disturbed. Our exposure to erionite must be limited as much as possible. People who work in construction and quarrying industries are most at risk from this disease as grinding and crushing rock is likely to reduce the size of the fibres making them more dangerous. If erionite is found in a construction area, we need to avoid exposing it to the atmosphere as much as possible and use appropriate health and safety measures when moving it around the city.

To mitigate the risk we really need to know where erionite is close to the surface and how much is transferred into the soil and the air when it is disturbed. Since erionite is not likely to be uniformly distributed, high risk areas need to be routinely tested prior to earthworks or construction. If Covid-19 has taught us anything, it is the importance of testing to reduce risk.