Workers building one of Sydney's tollway tunnels do not know whether they were exposed to potentially deadly silicosis because of a lack of monitoring, a union has claimed.
The Australian Workers' Union said requests to allow delegates carrying devices to track silica dust within the WestConnex Rozelle Interchange and Western Harbour tunnel were denied earlier this month.
John Holland, the construction firm behind the project, has now been hit with a test case in the Federal Court for "illegally hindering" AWU officials from using aerosol monitors to track the amount of dust within the tunnels.
"Tunnelling workers have the right to know what they'll be breathing in when they go underground," AWU NSW secretary Tony Callinan said on Monday.
"Unsafe levels of silica dust causes silicosis and silicosis can cause death. We know this to be true. So we will take action to ensure that workers are safe when they go to work."
Expressing deep concern for the levels of silica dust experienced by workers in the tunnelling industry, the union said John Holland breached employment law by denying union officials access to the site with a Dust Trak II device on May 1.
"Our officials should be able to bring dust monitors on site to inspect, if they suspect that there are safety breaches of the enterprise agreement. It's a very basic principle. But John Holland has consistently refused to allow these monitors on site," said Mr Callinan.
"We've asked John Holland again and again to allow dust monitors on site and they have refused. So now we have to go to court to confirm our right to conduct an inspection where we believe there is a safety breach."
The case is being run by plaintiff law firm Maurice Blackburn with principal Kamal Farouque saying the lawsuit was a test case about what rights union officials had when investigating suspected breaches of the law.
JohnHolland rejected the allegations, saying the health of its employees was its "number one priority" and that its air monitoring processes were "well-established".
The AWU was routinely provided with air quality test results from its sites, a company spokesperson told AAP.
"We comply with all relevant workplace health and safety regulations to ensure air monitoring on all of our sites, including the Rozelle Interchange Project, is of the highest possible standards," they said.
"The project does not restrict legitimate exercises of right of entry by union representatives."