The builder of the new $1.2 billion Perth Children's Hospital has not been blamed for asbestos found in ceiling panels but should have done more to protect the health of workers.
The asbestos was discovered inside fibre-cement ceiling panels in July by a worker who had been cutting into them, sparking fears he and his colleagues could suffer ill health from the exposure.
In his interim report on Tuesday, Building Commissioner Peter Gow said Chinese company Yuanda had provided the lead contractor, John Holland, a certificate labelling the sheeting asbestos-free.
Yuanda said that's what it had asked its suppliers for, but was instead provided with product containing asbestos without its knowledge.
Mr Gow said John Holland's procurement processes were "satisfactory", as were its clean up and remediation processes, but there was evidence it could have had better dust control.
"Any dust that comes out of construction has its hazards be it saw dust, stone dust, cement dust and so on; so people need to be very cautious that any dust is potentially hazardous," he told reporters.
The CFMEU accused John Holland of taking a cavalier approach to worker health, saying the report failed to address why the company didn't immediately halt work on the project.
"Furthermore, it appears the commissioner has failed to establish why it was that John Holland kept workers operating in the vicinity while tests were being carried out on the product," state secretary Mick Buchan said.
Mr Gow said Yuanda's inaccurate certificate showed builders needed to verify that the products they used did not contain asbestos.
"We need to work with our colleagues in other states to make sure there are proper processes in place to help builders, suppliers and specifiers to ensure they are getting what they expect," he said.
"We can't really be 100 per cent sure that these materials may not contain asbestos."
Boycotting Yuanda would be an overreaction, he said, but the company, which is being investigated by Border Force for suspected illegal imports, would need to improve its quality-control processes.
Yuanda Australia said the company took the concerns very seriously.
"The company is continuing its own thorough review to determine how incorrect products were used in the manufacturing process," it said.
