1960s photo of the Monaro Mall .

1960s photo of the Monaro Mall . Photo: Canberra Times

Thousands of Australians are believed to have been exposed to an American insulation product at the centre of the world's costliest asbestos scandal.

Zonolite, an American-mined vermiculite tainted with a deadly form of asbestos known as tremolite and linked to hundreds of deaths in the United States, was sold in Australia for more than 50 years.

Monaro Mall, 1973.

Monaro Mall, 1973. Photo: Canberra Times archives

An estimated 824 cubic metres of the product was painstakingly scraped from the underside of the roof of the Canberra Centre in 1988.

It was also used in home insulation and as a fire-resistant coating on major building projects.

Experts had identified the presence of asbestos in the vermiculite anti-condensation coating during the renovation and expansion program that rebranded the former Monaro Mall.

An image from The Canberra Times, Monday March 14 1963 edition.

An image from The Canberra Times, Monday March 14 1963 edition.

Regular testing over the past 25 years has found no further evidence of contamination at the site.

While the Canberra Centre material was disposed of in strict accordance with anti-asbestos laws that had come into effect four years earlier, the inspector, John Robson, did not make the connection with Zonolite at the time.

It continued to be mined and processed at Libby, Montana, until 1990. Asbestos activists now refer to the mountain community of 12,000, where hundreds of people have died from asbestosis, mesothelioma and malignant lung tumours and thousands more are critically ill, as ''the American Chernobyl''.

W.R. Grace, the owner of Libby's Zonolite mine since 1963, is one of the companies whose activities partly inspired the 1998 John Travolta film, A Civil Action. This was the story of an allegedly cancer-causing water contamination in Massachusetts in the 1980s.

Grace is about to sign off on two trust funds totalling more than $US4 billion ($4.6 billion) to cover future Zonolite-related compensation claims. This is more than twice the amount James Hardie has set aside for victims of its asbestos contamination.

The company has apparently taken no steps to make Australians aware of possible ill-effects from its products and has yet to provide details, despite repeated requests, for information on this, the amount of Zonolite shipped to Australia since the 1920s and where it was processed.

Grace says it is impossible for locals to take action against it through Australian courts even though the business has major operations in almost every state.

''The US court-issued injunctions (which are effective worldwide) require all claims based on asbestos exposure from Grace products or operations to be submitted to one of the trusts,'' Rich Badmington, vice-president, global communications, said.

W.R. Grace has been under Chapter 11 bankruptcy protection, the same legal shield invoked by the US car makers at the height of the global financial crisis, since 2001.

It is on the cusp of exiting this protection following the settlement of the final appeal to its multibillion-dollar reorganisation plan late last month. The company's share price rose from $75 in April 2013 to more than $95 just before Christmas.

John Robson, meanwhile, explains why Zonolite could not be identified as the asbestos culprit at the Canberra Centre a quarter of a century ago.

''As the products [used in coatings such as the one at the Canberra Centre] are generally not branded and were removed in 1988, the specific manufacturer is not identifiable,'' Mr Robson, now the manager of Robson Environmental, says.

''We were aware the vermiculite [sprayed under the roofing sheets of what had until then been known as the Monaro Mall] contained asbestos.''

Fairfax Media was only able to make the connection because of a full page advertisement extolling Zonolite's virtues in The Canberra Times on March 4, 1963. It was part of an advertising feature marking the opening of the Monaro Mall.

An accompanying article features a picture of a worker, apparently wearing no protective mask or clothing, applying the coating in the roof cavity using a long handled spray boom.

Brian McLeod, an occupational health and safety expert who has worked with Unions ACT, said he is aware of former Monaro Mall construction workers who later died of asbestos-related illnesses.

''There were at least two or three,'' Mr McLeod said.

It was the first time Zonolite's ''Spra-Insulation'' had been used in Australia and the distributors, Neuchatel Asphalte, were keen to drum up more business.

The year 1963 was not the first time tremolite-contaminated Zonolite products had been marketed in Canberra or elsewhere in Australia. They had been available for decades.

A Zonolite-derived loose fill insulation, branded as UniFil, was sold as a ''do-it-yourself product'' here and elsewhere from the 1930s.

Canberra's notorious ''Mr Fluffy'', Dirk Jansen of Kingston, may also have used a Zonolite product as loose fill insulation in the 1960s and 1970s. He almost certainly supplied and applied Zonolite as part of his vermiculite-coating sideline over the same period.

While vermiculite on its own is a safe substance, the Libby product - which is contaminated with tremolite - is not. Libby supplied an estimated 80 per cent of the world's tremolite needs in the 20th century.

It must be stressed that while the Canberra Centre is the inadvertent canary that has drawn attention to the ticking tremolite time bomb, there is no reason to believe any risk to the public remains following 1988's clean-up.

''There is no accessible Zonolite within the roof cavity … and a small amount of inaccessible Zonolite remains safely sealed and encapsulated in steel within a restricted, access-controlled plant room in line with strict legislative regulations,'' Canberra Centre senior centre manager Karen Noad said.

''Any death or illness relating to former work practices is deeply regrettable and our compassion and sincere sympathies go to the families of the workers.''