02/24/2015 11:17 EST | Updated 04/26/2015 05:59 EDT

Phosphine pesticide used in Fort McMurray apartment, 4 kids still in hospital

Four children remain in critical condition in separate Alberta hospitals, following the death of a baby, after all were exposed to illegal pesticides used to kill bedbugs in a Fort McMurray, Alta., apartment. 

An eight-month-old girl died Monday after she was exposed to phosphine, a fumigant.

The insecticide was brought into Canada illegally from Pakistan to fight a bedbug infestation, said the children’s aunt, ShaziaYarkhan.

The parents took the children to hospital Sunday. Two boys, aged two and six years old, were taken to the Stollery Children’s Hospital in Edmonton. Two others, aged four and seven, are in a Fort McMurray hospital.

The children’s mother remains under observation in the Fort McMurray hospital.

How bedbug substance works

Dr. James Kehrer, a pharmacy professor at the University of Alberta, said the substance was likely a metalophosphine, which would have reacted with moisture in the air to release phosphine gas.

“Phosphine itself is a colourless, clear gas that is quite toxic, and is often used as an insecticide, and sometimes actually as a rodenticide,” Kehrer told CBC News on Tuesday.

While some similar compounds used in pesticides, such as malathion, are generally safe for humans, organophosphates, including phosphine, break down in humans, causing bodily systems to fail, he said.

The pesticide acts on the nervous system in a manner similar to sarin gas, an outlawed chemical weapon, he said.

Once the gas was released, Kehrer said all family members would have inhaled it over several days — but noted that since it is a heavy gas, it would have been more concentrated near the floor where the children would have played.

Although not widely available in Canada, phosphine has been approved for use in other countries.

In Thailand, it was blamed in the mysterious deaths of two Quebec sisters, as well as several other tourists in 2012.

“People often think that the chemicals you can buy on your own are not as potent, and they’re often times right about that … but trying to use more potent chemicals — that requires a professional,” Kehrer said.

“Because, as in this tragic case, you can see there are consequences for using things without knowing how dangerous they can be.”

Kehrer noted that air circulation in the building has likely cleared the phosphine from the family’s apartment by now, and should not pose a risk to others living in the building.

Phosphine use in Canada

Canada’s Workplace Hazardous Materials Information System (WHMIS) classifies phosphine as a poisonous material with immediate and serious effects. Its health effects are listed as “very toxic.”

According to the Canadian Grain Commission, phosphine (also known as aluminum phosphide) is used to fumigate bulk grain in storage.

The commission notes its use should be carefully monitored, and should only be used in well-sealed structures.

In Canada, the fumigant can only be purchased with a licence, and only after the user has completed special training.