Australian forces in air and training missions in the Middle East are prepared for chemical weapon attacks by Isis, as coalition forces warn of an increased threat.

The Australian defence chief, Mark Binskin, offered an update on operations in Iraq and Syria during Senate estimates on Wednesday.

He said coalition partners had been aware of possible chemical weapons usage by Isis, also known as Daesh.

“The one area that we have increased our force protection that’s been an emerging threat … is the use of some limited chemical weapons by Daesh,” Binskin said.

He said chlorine weapons and sulphur mustard, known colloquially as mustard gas, were the biggest threats from Isis.

Mustard gas is a blister agent that causes severe burning when it comes in contact with skin. The United Nations’ chemical weapons convention banned the use of mustard gas and other chemical weapons in 1993.

Binskin said Australian troops, who were on the ground in Iraq on a training mission and engaged in airstrikes over both Iraq and Syria, had not been the target of chemical attacks.

Despite that, they remained prepared, the defence chief said.

“We have adapted our force posture to be able to respond to that [threat],” he said.

The Australian foreign minister, Julie Bishop, indicated in June that Isis was recruiting chemical experts to develop prohibited weaponry for use in Iraq and Syria.

“Daesh is likely to have amongst its tens of thousands of recruits, the technical expertise necessary to further refine precursor materials and build chemical weapons,” Bishop said. “The fact that atrocities such as this continue to occur shows that we must remain vigilant to the threat of chemical and biological weapons.”

Binskin outlined the cost of operation Okra, Australia’s air mission in Iraq, during his questioning in the Senate.

In the 2014-15 financial year, the operation cost taxpayers $159.4m and that figure was expected to rise to $390m this financial year.

In September, the then prime minister, Tony Abbott, announced that Australian airstrikes against Isis would extend beyond Iraq into parts of Syria.

Russia’s decision to enter the Syrian war, ostensibly to defeat Isis but also to bolster support for the Syrian president, Bashar al-Assad, had not changed Australia’s mission, Binskin said. However, he admitted it had added to the “complexity” of the conflict.

While the number of missions into Syria were “classified”, Binskin said there “have not been a lot”.

He said the rate of successful deployment of weaponry was in the “high 90s”.

About 530 weapons had been released since the start of the Iraqi mission, which was announced in October 2014.

The breakdown of missions over Iraq, conducted by various aircraft, are as follows:

• E74 wedgetails early warning aircraft – 150 missions

• KC-30A air-to-air refuelling aircraft – 430 missions

• FA18 superhornets – 210 missions

• FA 18 classic hornets – 250 missions

Canada’s prime minister-elect, Justin Trudeau, has rung Barack Obamato inform him that Canada will withdraw from the mission in Iraq and Syria.

Trudeau, who was elected on Monday, did not offer a timeframe as to when Canadian forces would pull out.

