Asbestos-containing dust discovered in multiple labs at the University of Toronto's medical-sciences building is causing concern over exposures to the dangerous material, and has prompted a union and faculty association to warn members not to even enter the building.

The university's medical-sciences building is one of the biggest on campus. A major renovation of the almost 50-year-old facility, which also involved asbestos abatement, began last November. In the past two months, test results have shown asbestos in the dust in several labs. Two remain closed.

"We've advised our members that they should not enter the building, for any reason, until further notice," said Ryan Culpepper, chair of CUPE 3902. "We've also advised them to file an incident-exposure report to WSIB and to go see their doctors, because we don't know at this point the extent of the contamination."

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The university was "very slow to notify anyone that anything was going on," he added, noting that some of the cleaners are now worried about the dust they've been wiping up over the past few months.

Asbestos is a known carcinogen and the World Health Organization says there is no safe threshold for exposures. Canada has banned asbestos use, by 2018, though the U of T case illustrates the challenges of dealing with the mineral's legacy.

The U of T's Faculty Association questioned the university's handling of the situation, saying it is "extremely concerned that asbestos contamination may have adversely affected our members as well as students and others at the MSB, and that their health and safety continue to be at risk."

Students are also concerned. The university "did not provide information to the graduate students in the affected labs in a timely manner," said Andrea Constantinof of the Graduate Students' Union.

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Once students were told about the situation, "it was unclear as to whether the labs were hazardous for them to re-enter," she said, adding that it was only after grad students signed a petition that the university provided more information about the asbestos.

Earlier this year, people reported encountering dust in their sixth-floor lab. Testing confirmed asbestos in the dust. The lab was closed, and so were two others.

On Feb. 24, "unusual dust" was again reported, in another area, notes a message sent a week ago from Trevor Young, dean of the Faculty of Medicine. More asbestos was found.

Then, in March, tests showed another problem, on the third floor – the presence of asbestos fibres, which appear to be from a sealer used in the wall, that emerged from drilling.

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The first two cases likely relate to the abatement work, where dust escaped the work area because it wasn't properly sealed off.

The university notes that of the 243 air-quality samples taken since last fall, all tests have shown levels "well below" the occupational-exposure limit for asbestos.

That said, tests of the dust in some of the labs have shown the presence of asbestos.

Asbestos dust has only been found in the building's research tower, and no common areas, classroom lecture areas or teaching areas have been involved, Scott Mabury, vice-president of university operations, said in an interview.

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He acknowledges that mistakes were made, including not sealing off the work area properly. And, he added, communication, especially in prior weeks, could have been better.

Asbestos is commonly found in public buildings. University and public schools across Canada are dealing with asbestos challenges, and spending millions of dollars on abatement efforts.