The Department of Primary Industries, Parks, Water and Environment (DPIPWE) has suspended fumigation at a fruit fly control zone while it investigates concerns four of its staff may have been exposed to the potentially dangerous pesticide methyl bromide.

What is methyl bromide? It is a colourless gas or volatile liquid

It is a colourless gas or volatile liquid It's used as fumigant against insects, termites, rodents, weeds, nematodes, and soil-borne diseases

It's used as fumigant against insects, termites, rodents, weeds, nematodes, and soil-borne diseases Symptoms of poisoning may include headache, dizziness, nausea, chest and abdominal pain, and mental confusion

Symptoms of poisoning may include headache, dizziness, nausea, chest and abdominal pain, and mental confusion May also cause liver, kidney and central nervous system damage as well as paralysis, convulsions, comas and brain damage

Biosecurity workers have been working to contain a fruit fly outbreak in Tasmania following the discovery of larvae and adult fruit flies found in apricots at Spreyton, soon after the pest was detected on Flinders Island.

Last week Biosecurity Tasmania was conducting tests on a suspected male fruit fly found at George Town in Tasmania's north — well east of the edge of the control zone.

Now the DPIPWE has been forced to suspend its fumigation activities, after four staff fell ill.

In a statement, a DPIPWE spokeswoman said the incident happened at the fumigation site set up at Devonport in northern Tasmania.

"DPIPWE has voluntarily suspended fumigation activities until further notice while the investigation is underway," the spokeswoman said.

"Four DPIPWE staff were potentially exposed to methyl bromide during fumigation work on Tuesday 13 February.

"DPIPWE reported the incident to WorkSafe Tasmania and the CPSU [Community and Public Sector Union] on the morning of Wednesday 14 February after two staff reported feeling unwell.

"DPIPWE has commenced its own investigation into the incident."

Union warns against exposure to methyl bromide

The CPSU's Tom Lynch said the workers had been at the Devonport Airport where a contractor was fumigating fruit from the control zone.

"This was the site that had been set up so that fruit could be fumigated and taken out of the control zone," he said.

"One of them reported to Mersey Hospital and was kept in overnight for observations. The others, as I understand it, attended their doctors.

"All of them have been blood tested. I understand blood tests will show if they have been exposed to methyl bromide."

Mr Lynch said the symptoms had passed, but the workers faced an anxious wait for test results.

"Unfortunately it will take three weeks for those tests to come back, so in the meantime you have a group of workers that are going to sit and worry about whether they have actually been exposed," he said.

"It is now about whether they were exposed, the degree of the exposure and whether there are long-term risks to them.

"You don't want to expose yourself to any chemical, and methyl bromide is one of those chemicals you want to avoid at all costs."

DPIPWE 'unprepared': union

Mr Lynch said the DPIPWE had been unprepared for the fruit fly outbreak.

"I think at the end of the day it will be found that the [fruit fly response] arrangements were probably all a little bit rushed," he said.

"We have been complaining for a long time that Biosecurity is understaffed.

"I think under-resourcing in Biosecurity is partly to blame for the fruit fly incursion in the first place, and for the effectiveness of the response.

"This incursion is getting worse at this stage, not better."