Ambulance Employees Australia state secretary Steve McGhie said he had written to Ambulance Victoria asking for a risk assessment into penthrane.

Paramedics, including those in Ballarat, usually use penthrane as an initial method of pain control, before morphine.

It has been banned in America due to concerns it may be carcinogenic.

It is also no longer used by West Australian paramedics and its use is restricted in both New South Wales and Tasmanian ambulance services.

"We're requesting it be removed until a risk assessment is done," Mr McGhie said.

While he said it posed no risk to patients, due to the small amount of dosage received, it was a danger to paramedics, who were regularly inhaling escaped fumes.

"In recent times there's been a number of paramedics struck down with cancerous type illnesses who have hit the 20-year mark or more.

"We think it's too much of a co-incidence."

But Ambulance Victoria executive general manager education and professional standards Tony Walker said it had received advice the drug was quite safe in the dosages used.

"But we're happy to work with the union and do a risk assessment," Mr Walker said.

He said specialist medical advisors would test penthrane in the back of an ambulance and assess its suitability for continued use.

"We're quite comfortable the drug is safe but we will undertake the risk assessment."

But Mr McGhie said there was evidence penthrane was highly toxic and could affect the kidneys and liver.

In NSW, paramedics can only administer penthrane twice in one shift and it can only be given in well-ventilated areas in Tasmania.

"We'll be happy to keep using it if there is no effect on paramedics.

"But they thought asbestos was safe 50 years ago too."