Scientists are warning of the potential cancer risk for construction workers from fibres that could be released from volcanic rock found in the Auckland region.
The fibres come from a rare mineral called erionite, which is in silica-rich volcanic rock found in many parts of the world, including in the Auckland region.
Researchers say dust containing erionite can become airborne once disturbed, and if it is inhaled can potentially cause malignant mesothelioma, a disease more usually associated with exposure to asbestos.
Though the mineral is rare, it is possibly present in rock under Auckland's large projects, and testing should be done before earthworks are carried out, they say.
In an article published in the New Zealand Medical Journal, researchers from the University of Auckland and Unitec Institute of Technology say international research shows erionite is an emerging occupational and public health risk.
Associate professor Martin Brook from the University of Auckland, co-author of the article, said New Zealand should be thinking about a standard for erionite exposure and how to test for it.
"Two million tonnes of rock was removed for City Rail Link project and potentially at least some of that rock could contain erionite. But currently there are no international or New Zealand occupational exposure limits or standard low-cost field sampling and analytical methods for erionite."
International studies have also shown that people working in the construction or quarrying industries are most at risk, associate professor Jennifer Salmond said. Anyone at risk from exposure should be wearing full protective gear because it's likely erionite fibres can be carried on clothing.
The researchers said New Zealand's rate of malignant mesothelioma is high by international standards but no-one knew exactly why.
Brook told Nine to Noon the dangers of erionite emerged in Turkey in the 1970s when villagers died from what was initially thought to be asbestos exposure.
He said it is a rare mineral but is in parts of the Auckland region, so it is worth finding out where it is and avoid having people come in contact with it.
Salmond said the mineral had since been found in Italy and the United States, and people were beginning to gain more understanding of the risks.
"In North Dakota they inadvertently used rock material which that contained erionite in some of the roads they were making and scientists then found erionite fibres all through the community, including on school buses. It was recognised as an emerging hazard in the US in about 2011.
"So we're starting to build a case that erionite is more dangerous than we first thought.
"Now is the time that we need to start thinking about how much of a risk this is to Auckland, because we just don't know.
"We need to know where it is and how much we are likely to be exposed to it."
Salmond said tests should be be done at the City Rail Link project
It was not something the public need to worry about, she said, but the engineering community and regulators should be aware of the risk.
"This is something we need to be aware of, it's something we need to start looking for and we need to start testing for before we do earthworks in areas where this rock is to be found."
If the fibres are undisturbed the risk is negliable, she said.
"And even if we do disturb the rock, this is a rare mineral."