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.