Erionite exposure in New Zealand

A. Erionite is a naturally occurring fibrous mineral found in some volcanic soils and sedimentary rock layers formed from ejected volcanic ash (known as ‘tuff’). It belongs to a group of minerals called zeolites, a few of which can have physical properties similar to asbestos.

Like asbestos, erionite exposure has been linked to certain lung disorders and cancer. In particular, prolonged exposure to airborne erionite fibres increases the risk of malignant mesothelioma, a rare but aggressive cancer of the linings of lungs and other organs.

sampling in cliffs and SEM image of erionite.

We know that erionite and other similar rocks known as zeolites are present in some underground sedimentary rock formations in the Auckland region. This is not surprising, given the volcanic terrain upon which the city was built.[1]

If undisturbed, these erionite deposits pose little to no risk. However, erionite fibres can be released into the air from weathering of erionite-containing rocks (for example, on cliff faces where the rock layer is exposed to the wind and rain) or during excavation work and tunnelling through these rock layers. This means that people in New Zealand, and particularly workers involved in excavation works in certain areas, could have some exposure to airborne erionite fibres.

Excavation activity in the Auckland region can potentially expose rock layers containing erionite, and generate dust containing the toxic fibres. The amount of erionite present in the rock, and how much airborne fibres may be generated by these activities, is not yet understood. This is why the University of Auckland team is conducting the current study. Soils can contain erionite fibres, but we have not found any in soils in Auckland. However, at the moment we don’t know enough about how much, and exactly where, erionite is present in the rocks to understand the risks to the public or to people working in construction and other earthwork industries. That is what the Auckland University study is trying to find out.

[1] Zeolite deposits are present in the Waitakere Group volcanic rocks and the Waitemata Group sediments – these are dispersed around the Auckland region.

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A. When erionite is inhaled it has been found to increase the risk of lung diseases and malignant mesothelioma, a rare disease that is usually considered to be a result exposure of asbestos. The risk from erionite exposure was first discovered when a very high rate of mesothelioma was observed in three small villages in the Cappadocia region of Turkey in the 1970s. The people in the village were not exposed to unusually high levels of asbestos, and their mesothelioma cases were later linked to the presence of erionite in the distinctive rock formations characteristic of the surrounding landscape. The soft, powdery rock had long been excavated to make caves, churches and underground dwellings, and was used as building blocks for the village houses. Erionite has not been found in these concentrations in Auckland and as far as we know, rocks containing erionite have not been used in the construction of buildings.

The International Agency for Research on Cancer (IARC) listed erionite as a carcinogen (a cancer-causing substance) based on confirmation of evidence of health effects from the Turkish villages, and additional international research in experimental animals, which have shown erionite to be more potent than asbestos in causing malignant mesothelioma.

However, the toxicity of erionite, and the risk of disease development in an exposed population, is thought to depend on several factors, including a genetic predisposition which makes some people more likely to develop cancer which was found among the Turkish villagers (see Q4). Increased incidence of mesothelioma has not been observed in other parts of the world where it is present in the rocks and soil, but not used in residential buildings. However, this research is in its early stages and complicated by small population sizes and the difficulties of tracking the health outcomes of mobile populations who may have been exposed but subsequently moved out of the area.

A. Some people are thought to be particularly susceptible to developing health effects from asbestos-like fibres because they have a certain genetic trait that predisposes them to mesothelioma and other cancers. The genetic trait – a mutation in the tumour-supressor gene BAP1 – was first identified in related families in the Turkish villages in Cappadocia, where the link between erionite and malignant mesothelioma was first discovered. All of the villagers were highly exposed, living their entire lives in the presence of erionite dust, but those who developed mesothelioma were all from related families that had the BAP1 mutation. Other villagers with similar lifetime exposures did not develop mesothelioma and were apparently less susceptible to erionite’s effects.

Some members of these families moved to Sweden and the USA and other places, and the susceptibility to cancer was carried with them and where the individuals had been exposed to erionite in Turkey as children, many went on to get malignant mesothelioma.

It is not currently known whether the genetic trait is present in any families in New Zealand. Other mutations that affect tumour suppressor genes, and in particular those responsible for DNA repair, might also increase the susceptibility to environmental carcinogens like erionite to some extent. Thus it is impossible to know who might be more susceptible to developing cancer after exposure to erionite in New Zealand.

It is therefore important to understand the potential for encountering erionite, and to limit or avoid exposure where possible.

A. A ‘safe’ level of exposure to erionite has not been established, and given its known toxicity, any exposure should be minimised or avoided where possible. That said, we know that health effects likely depend on the amount of erionite inhaled, and the time period to which people are exposed. Short, low-level exposures are less likely to have any notable effects. However, elevated risks may be anticipated in some occupational settings that involve excavation through sedimentary rock layers where erionite is present. This may be of concern for construction workers or others exposed to construction dust over a period of time, if dust controls are not in place. The risk of developing disease from inhalation of fibres likely increases with cumulative exposure over time. However it is very difficult to link exposure to disease outcomes as it takes 20-60 years for cancers to develop following exposure.

It is likely that the risk of exposure for the general population is much lower than in occupational settings, because the exposures would most likely be short-term or involve a much lower concentration of airborne fibres. However, there is potential for members of the public to be exposed to erionite in the immediate vicinity of construction activities in areas where erionite is found, especially if it is dry and dusty. Earthwork and construction industries work hard to reduce exposure to dust both onsite and offsite, as breathing in dust presents a health hazard even when it does not contain erionite, which mitigates this risk. People may also be exposed to erionite from exposed areas in cliff faces. However, it is likely that exposure to erionite from natural weathering processes is not a significant problem in Auckland as natural weathering processes have been going on for years and we have not observed any unusual patterns of disease.

There is a concern that the exponential increase in construction activities in previously undisturbed areas may lead to increased exposure to erionite fibres if the work occurs in areas where erionite maybe found and disturbs unknown or unexpected deposits of erionite. Tunneling operations and large construction projects involving extensive earthworks consider the possibility of disruption of erionite-containing soils, and what that means in terms of health and safety for workers and the public to ensure everyone is kept safe. In general though, the risks associated with low-level environmental exposure to erionite are poorly understood and our project is working to understand and quantify these in the New Zealand context. Since erionite is present in New Zealand, development of malignant mesothelioma from erionite exposure cannot be ruled out in the future.

A. Asbestos exposure is known to increase the risk for a number of lung diseases and cancers, but most specifically malignant mesothelioma. New Zealand and Australia are among a number of high-income countries with elevated incidence of mesothelioma,[2] although it is still considered a rare disease.

Asbestos-related disease diagnoses and deaths in NZ occur mainly in older age groups (and mainly in males), usually resulting from occupational exposures that occurred several decades in the past. This is because the diseases typically develop long after the actual exposure – sometimes up to 60 years. This is called a ‘latency period’, and it is influenced by both the intensity (concentration/quantity of fibres inhaled – the ‘dose’) and the duration of the exposure (the cumulative amount breathed in over time).

At this point, human dose–response data are not available for erionite. This means that we don’t know precisely how much erionite an average person can be exposed to before the risk of disease development becomes significant, but it is still expected to show a long latency period.

[2] These countries conducted activities such as asbestos mining, production of asbestos-containing materials, or extensive use of asbestos in construction, ship building and other industries.

A. Some studies have suggested that erionite is more toxic than asbestos in causing mesothelioma. This is based on laboratory experiments and animal studies,[3] and the observation of a very high incidence of erionite-induced malignant mesothelioma observed in Cappadocian villages in Turkey. However, the clusters of mesothelioma cases in Turkey have been linked to a familial genetic predisposition to fibre-induced cancers, and in people who were exposed to high concentrations erionite in their homes, village buildings and in the rocks and soils around them, so the rate calculated based on studies of these clusters is not applicable to the general global population.[4]

The potency of different types of asbestos-like fibres to cause disease depends on their physical and chemical characteristics. Although human data for erionite is more limited, erionite fibres share some of the properties of the more potent forms of asbestos that are thought to contribute to their carcinogenicity.[5] Differences in the chemical composition and structures of the fibres affect their toxicity and persistence in lung and pleural tissues, making them more or less likely to cause cancer.[6] There may be differences in composition of erionite found in different locations that may make some sources more toxic than others.

[3] Malignant mesothelioma was induced with a lower volume of erionite fibres and in a shorter time period compared with crocidolite asbestos. (Wagner et al., 1985)

[4] The rate of MM in one of the villages was ~1000 times greater than in the general population of industrialised countries

[5] Critical parameters include the length-to-width ratio of the fibre, which determine how the fibres persist in the lung and activate macrophages and the chemical content (silicon, iron, and magnesium oxide) which determine toxicity

[6] Factors affecting toxicity include fibre size (and length to width ratio), durability, and iron content – the latter because of its ability to induce oxidative stress in cells in the lung (Korchevskiy et al., 2019)

A. The University of Auckland study will be analysing the chemical and physical structures of Auckland erionite samples for comparison with other known carcinogenic fibres, to help determine their relative toxicity for causing cancer.

With asbestos, long, thin fibres are considered more dangerous because they are more difficult to clear from lung tissue. According to the IARC, Turkish erionite contains a higher proportion of longer fibres (> 4 μm) than erionite from Oregon, USA or New Zealand.[7]

Studies comparing the erionite from Oregon and NZ for their ability to induce mesothelioma responses in rats found that Oregon erionite  produced mesotheliomas in the majority of animals within a few months, whereas the New Zealand sample had produced none. This was attributed mainly to difference in the concentration of the thinnest class of fibres in the samples – the Oregon sample contained 10x more of these types of fibres.[8] However, the exact nature of the erionite present in NZ is still being investigated as part of the University of Auckland study.

[7] Turkish erionite contains a higher proportion (32%) of longer fibres (> 4 μm) than erionite from Oregon, USA (11%) or New Zealand (8%). New Zealand and Oregon erionites contain 2–3% of thicker fibres (> 1 μm). (IARC, 2012)

[8] See Ilgren et al., 2008

A. Risk assessment asks: ‘What are the risks?’ and ‘Who will be affected, how, and to what extent?’ It includes hazard identification, dose–response assessments, exposure assessments, and risk characterisation.

Erionite, like asbestos and other related fibres, has been clearly identified as a hazard. Also like asbestos, erionite is likely to cause cancer in a dose-dependent manner. That means that the greater the exposure, and the longer the time of exposure, the greater the risk of contracting an erionite-related disease. However unlike asbestos it is much less prevalent in urban environments.

We therefore need to consider the dose–response of the health effects from exposure to erionite – in other words, the amount of exposure (number of fibres, inhaled over time) that leads to effects. There is no known ‘threshold’ for a safe exposure. That is why it is recommended to keep exposure to these types of fibres as low as possible.

A. Until we know more about the characteristics and quantity of erionite in the Auckland region, we need to work on reducing risk that people come into contact with erionite without realising it. We are working to achieve this by educating people who work in industries which disturb rocks which may contain erionite how to detect its likely presence or absence in their work areas. This includes increasing awareness about the types of rock formations where erionite is likely to be found, screening methods to identify the presence of marker minerals commonly found with erionite but more easily detected (such as other types of zeolites), as well as teaching safe sampling and accurate testing procedures. Other measures that can reduce the risk of the exposure of employees to respirable erionite fibres include: listing the possible presence of erionite in the project’s geotechnical risk register, and adequate dust control techniques (this might include scheduling tasks that generate most dust on rainy days or when soil is damp) and where appropriate the use of masks and other protective equipment.

 In occupational settings where workers are deemed very likely to be exposed to erionite, personal protective equipment (PPE) including well-fitting respiratory masks can be used as a precautionary measure to reduce the risk of fibre inhalation. Employees working in dusty areas should change into clean clothing before leaving the worksite, and PPE and other equipment should be washed regularly to remove dust and other contaminants. This prevents fibres from being carried off the worksite on clothing and equipment.

A. Unlike asbestos, there are no regulatory or consensus standards or occupational exposure limits (OEL) for airborne erionite fibers. Before an OEL can be established, a standardized, validated exposure assessment method needs to be developed, which will allow a quantitative evaluation of risks associated with given exposures.

A. This is the first comprehensive study of erionite in New Zealand, with a focus on the potential risks to people who may come into contact with disturbed erionite deposits in Auckland.

 Specifically, the study aims to:

• • Develop techniques to identify erionite in the field in fresh excavations, soils and other environments;
  • Develop geological models of the distribution and concentration of erionite in key regions (in particular, in Auckland);
  • Monitor the airborne transport and dispersal of erionite;
  • Use this information to provide models which improve our assessment and understanding of the risks of exposure to erionite in New Zealand
  • Work with industry partners, to develop guidance for safe management of environmental and occupational risks for exposure to erionite. 

Baris YI. Asbestos and Erionite Related Chest Diseases. Ankara-Turkey 1987:36-102

Beaucham, C., King, B., Feldmann, K., Harper, M., Dozier, A., 2018. Assessing occupational erionite and respirable crystalline silica exposure among outdoor workers in Wyoming, South Dakota, and Montana. J. Occup. Environ. Hyg. 15, 455–465. https://doi.org/10.1080/15459624.2018.1447116

Ilgren, E.B., Ortega Breña, M., Castro Larragoitia, J., Loustaunau Navarrete, G., Fuentes Breña, A., Krauss, E., Fehér, G., 2008. A Reconnaissance Study of a Potential Emerging Mexican Mesothelioma Epidemic due to Fibrous Zeolite Exposure. Indoor Built Environ. 17, 496–515. https://doi.org/10.1177/1420326X08096610

Korchevskiy, A., Rasmuson, J.O., Rasmuson, E.J., 2019. Empirical model of mesothelioma potency factors for different mineral fibers based on their chemical composition and dimensionality. Inhal. Toxicol. 31, 180–191. https://doi.org/10.1080/08958378.2019.1640320

Wagner, J.C., Skidmore, J.W., Hill, R.J., Griffiths, D.M., 1985. Erionite exposure and mesotheliomas in rats. Br. J. Cancer 51, 727–730.