Nearly a thousand electrical panels containing asbestos have been installed at substations across Sydney and most of it is being left in place.
Seven News can reveal the Malaysian-made equipment somehow eluded customs despite asbestos being banned in 2003.
It's left hundreds of workers potentially exposed.
"We shouldn't have any asbestos equipment in the place, but somehow or other this bit of asbestos just slipped through a few nets,” said Ross Trevor, a former Ausgrid employee whose job it was to identify and remove asbestos from the power grid.
The 968 gear switch panels manufactured in Malaysia were imported and installed at 51 sites between 2007 and 2014.
Ausgrid's own tests found white and brown asbestos which cause lung cancer, mesothelioma and asbestosis.
By the time it was identified workers had been exposed for months, perhaps years.
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"They were all around about your face height which is your breathing zone so I'd say that the people who install that equipment probably put themselves in the worst position possible,” Mr Trevor said.
There is no safe level of exposure to asbestos.
"In the long term, this is a death sentence for those workers," said Barry Robson, the President of the Asbestos Diseases Foundation of Australia.
"And they won't know they've got any disease, 20, 30, 40 years from now they might, they might, present with an asbestos-related disease… now they've got to live with that, and their families,” Mr Robson said.
Ausgrid, which is owned by the state government, at first ignored our questions about how the asbestos got through customs and who was in charge of that at the company.
They later wrote: “When we became aware of this matter, Ausgrid immediately wrote to Tamco asking them to fully investigate how this occurred and to undertake immediate action to prevent it from occurring again.
"We made them aware of their obligations under the Workplace Health and Safety Act and asked them to report the incident to WorkCover and the Australian Customs and Border Protection Service. We also reported the matter to WorkCover NSW.”
They also claimed to have safely managed the risk to workers, a claim rejected by the Electrical Trades Union and the Asbestos Diseases Foundation of Australia, which wants Ausgrid to screen the lungs of all exposed workers.
“My message to the Ausgrid workers is to contact here in NSW the dust diseases board… get Ausgrid to contact the board and have all of their workers screened… the mobile, what they call the lung bus, should visit each and every one of the work sites and every worker who's been exposed should be put through the dust diseases bus,” Mr Robson said.
“The flow on effect here is if they don't know they're being exposed, so they're working unprotected, then it'll get in their clothing, their hair, they'll jump in the car and go home, pickup the kids or the wife or whatever and the possibility of passing on the fibres to the family,” Mr Robson said.
Deemed too expensive to remove, most sites have been cleaned and sealed.
"Well I don't think it is good enough. I think if you find asbestos anywhere it should be removed,” said David Mier, the ETU Assistant National Secretary.
The Malaysian manufacturer TAMCO also lists as clients Energy Australia, Integral Energy and Optus.
The Electrical Trades Union and former workers fear new asbestos will continue to get past authorities.