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."