TORONTO - A new report shows former Ontario government workers who were exposed to dangerous levels of a powerful herbicide from the 1950s to the 1970s face an elevated risk of disease.

An expert panel spent two years looking at the widespread use of 2,4,5-T — a dioxin-laced chemical found in Agent Orange — by workers at Ontario Hydro, the Ministry of Natural Resources and the Ministry of Transportation.

Some former government workers who used the chemicals to clear brush and hydro corridors believe it is responsible for their cancers, but the panel did not make a direct link between elevated exposures and getting sick.

The panel said even when exposure estimates exceed safe threshold levels "adverse health effects may not occur."

Natural Resources Minister David Orazetti says people who think they may have gotten ill because of their exposure to the herbicide should contact the Workplace Safety and Insurance Board to file a claim.

Orazetti warns they will need medical evidence to prove their illness came from exposure to 2,4,5-T.

Critics point out the WSIB has nearly 400 open cases from workers who claim the herbicide is to blame for their cancer, and say the report merely gives the agency and the government more time to drag their feet.

Panel chair Dr. Leonard Ritter defended the decision not to make a direct link between exposure to the chemical and cancer or other illnesses.

"The risk assessment only indicates that an acceptable margin of safety has been exceeded based on the methodology we used for certain occupationally-exposed groups, and that their health could have been affected, but not necessarily so," he said.

"The panel concluded that the risk of disease due to bystander exposure to 2,4,5-T would be very low."

The provincial workers weren't the largest group exposed to the highly toxic herbicide, but the panel's mandate was limited in scope, added Ritter.

"Most use of the herbicide in Ontario was not by the government of Ontario but rather by private and municipal users," he said.

"The assessment of these non-government uses was beyond the panels' scope and not included in the evaluations."

The New Democrats said the report was aimed at limiting the government's exposure in the event of costly lawsuits.

"The report acknowledges that exposures were much higher than the safe amount, but it also puts the onus of proof on the victims by directing them to WSIB and treating them as individual cases," said NDP house leader Gilles Bisson.

"What about workers that have passed away as a result of cancers knows to be related to Agent Orange?"

Bisson accused the Liberal government of skirting its responsibility by asking the workers to prove their sickness.

"This report uses the same tactics that were used against gold miners and their widows when fighting for compensation against lung cancer."

Orazetti said the Liberal government would study the report to determine if it should take further action, and suggested the WSIB would quickly move to deal with any claims from the workers exposed to 2,4,5-T.

"There are efforts being made within WSIB to have a team of individuals to address this particular group of claimants, and medical evidence will need to be provided to make that correlation as in any other claim that comes before the WSIB," he said.

Also on HuffPost:

Loading Slideshow...
  • A warning sign stands in a field contaminated with dioxin near Danang airport, during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. The sign reads; "Dioxin contamination zone - livestock, poultry and fishery operations not permitted." (AP Photo/Maika Elan)

  • In this photo taken on Wednesday, Aug. 8, 2012, Le Van Tam, 14, is picked up by his father at a rehabilitation center in Danang, Vietnam. The children were born with physical and mental disabilities that the center's director says were caused by their parents' exposure to the chemical dioxin in the defoliant Agent Orange. On Thursday, the U.S. for the first time will begin cleaning up leftover dioxin that was stored at the former military base that's now part of Danang's airport. (AP Photo/Maika Elan)

  • In this photo taken on Wednesday, Aug. 8, 2012, Chu Thanh Nhan,12, watches other children dance at a rehabilitation center in Danang, Vietnam. (AP Photo/Maika Elan)

  • In this photo taken on Wednesday, Aug. 8, 2012, Chu Thanh Nhan, 12, sits in an empty classroom at a rehabilitation center in Danang, Vietnam. (AP Photo/Maika Elan)

  • In this photo taken on Wednesday, Aug. 8, 2012, Vo Y, background, rests with other children during nap time at a rehabilitation center in Danang, Vietnam. (AP Photo/Maika Elan)

  • A Vietnamese soldier stands guard near a field contaminated with dioxin to prevent people from going close, during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • Maps of the area contaminated with dioxin around Danang airport are displayed during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • Attendants sit next to a field contaminated with dioxin before a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • David Shear

    U.S. Ambassador to Vietnam David Shear delivers a speech during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • Vietnamese delegates attend a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • A yellow flag marks a field contaminated with dioxin near Danang airport, during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • With the backdrop of a field contaminated by dioxin, Vietnamese delegates attend a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)

  • U.S. delegates visit a field contaminated with dioxin near Danang airport, during a ceremony marking the start of a project to clean up dioxin left over from the Vietnam War, at a former U.S. military base in Danang, Vietnam Thursday Aug. 9, 2012. (AP Photo/Maika Elan)