Some people working to rebuild Christchurch have been exposed to high levels of a chemical compound linked to lung disease and other health hazards.

A WorkSafe pilot study of 39 dust samples taken from construction sites found what a public health expert called "high levels" of silica.

WorkSafe said the report also raised concerns about a lack of efficient dust suppression methods and many construction workers not using respiratory protection.

For Christchurch construction workers, the silica risk was not evenly distributed. Massey University Professor Bill Glass said the study chose to test dust samples from what researchers knew where the "worst types of tasks" in terms of dust exposure during concrete work.


"When these tasks were looked at - cutting and grinding and smoothing of concrete - the results were significantly higher than the standards that currently exist in New Zealand, the standards that exist in the UK, which are more stringent, and the standards that exist in the US, which are more stringent, too."

Professor Glass said the pilot study confirmed these tasks produced "high quantities" of small, invisible silica particles that could damage the lungs.

He said the level of danger silica presented depended on the frequency and intensity of exposure to the dust.

Although silica was long ago established as a cause of the lung disease silicosis, Professor Glass said a person needed massive, ongoing exposure to silica to get that disease.

Gold miners in Waihi a century ago were the types of people who got silicosis, which was now extremely rare in New Zealand.

"By wearing relatively simple dust protection masks and using wet methods of cutting or grinding ... and given the relatively short exposure time, then the likelihood of developing silicosis is very, very slim."

Professor Glass said there was some evidence chronic bronchitis and chronic obstructive pulmonary disease could arise from long-term intense exposure to silica.

He said silica was now a designated carcinogen, or cancer-causing agent and this was another good reason to reduce silica exposure at work.


The pilot had raised an important issue but further studies on related topics would be useful in improving knowledge of silica-related health risks, he said.

"There is evidence silica can damage kidney function ... it's not just a simple product that damages the lungs."

Professor Glass had straightforward advice for the industry.

"The message is, it's really one of controlling dust at work, rather than focusing on silica in itself."

He said most companies were doing a lot to improve the situation. But he said a few cowboys in the wider industry unfortunately had casual attitudes.

Professor Glass said it was important the industry now addressed the silica issue.

WorkSafe project manager Donna Burt said the new data suggested control measures in the construction industry needed reviewing, to ensure workers were protected from adverse respiratory effects.