TasNetworks is now speaking with 49 people who were potentially impacted by toxic chemicals through their work with the Hydro-Electric Commission between the 1960s and 1980s.
Dr Roger Drew, the toxicologist commissioned by TasNetworks to help investigate this matter, reviewed scientific literature regarding potential associations between the chemicals 2,4,5-T and 2,4-D and medical conditions, including cancer.
The Melbourne-based toxicologist confirmed these chemicals were "commonly used throughout the world for controlling vegetation beneath power lines, forestry access routes and rail lines".
"At that time they were considered safe," Dr Drew said.
Concern was raised in the 1970s about "a particular dioxin" present in 2,4,5-T due to the way the herbicide was made. This dioxin was not in 2,4-D.
"At this time, we do not know what the dioxin level was in the 2,4,5-T purchased by HEC," Dr Drew said.
However, WorkSafe Tasmania chief executive Mark Cocker said it was possible former HEC employees may have been exposed to 2,4,5-T containing the dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) at "levels that are no longer considered acceptable".
"It is understood that a number of scientific studies have recognised possible links between high exposure to TCDD and an increased risk of certain cancers, skin conditions and, possibly, other health effects," Mr Cocker said.
Dr Drew also said, "high exposure to dioxin is associated with induction of some cancers in humans but it has weak potential for this, and only a few persons exposed are susceptible".
"At this time we have no clear information indicating the chemicals used by HEC have caused harm to HEC workers, this is part of the focus of the investigation," he said.
The World Health Organization's International Agency for Research on Cancer evaluated TCDD in 1997 and 2012 and classified the dioxin as a "known human carcinogen".
Maximum levels of TCDD in 2,4,5-T started being regulated in 1976, with all products containing 2,4,5-T withdrawn from the Australian market from 1982, reducing the workers' risk of being exposed to those toxic chemicals.
If you think you may be affected visit tasnetworks.com.au, worksafe.tas.gov.au or phone 1300 366 322.
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