As the world’s temperatures surged to the hottest month on record in July, the deaths of four Canadian firefighters battling blazes were mourned as rare, tragic accidents suffered in the line of duty. 

But Vanisha Sukdeo, a Toronto-based lawyer whose work focuses on corporate and labour law, said they’re indicative of how rising temperatures are making jobs more dangerous for outdoor workers, many of whom can’t simply stop working when the heat becomes unbearable. 

A rise in extreme heat across much of the world this year has shone a spotlight on workers’ safety, raising the question among policymakers and employers: how hot is too hot to work? 

Sukdeo—who has a forthcoming book on the topic with publishing firm Irwin Law—said in Canada, the answer is open to interpretation. 

“There is in place, under labour and employment law, the right to refuse unsafe work,” she said. But that law is vague and doesn’t include clear rules for things like at what temperature workers should take a break, said Sukdeo, or how long and frequent those breaks should be. “That language is missing,” she said, adding that existing protections under the act are “not enough.” 

Last week, the Ontario government proposed regulations to protect workers from heat stress under the province’s Occupational Health and Safety Act (OHSA), using guidelines set by the American Conference of Governmental Industrial Hygienists (ACGIH). The rules would require workplaces where OHSA applies to limit work under certain temperatures, and provide workers with training on how to recognize signs of heat-related illnesses.

“Due to changes in our climate, extreme heat events are a growing health risk to workers in Ontario,” a consultation paper for the proposed changes reads.

Other provinces, including B.C. and Nova Scotia, already require employers to follow ACGIH guidelines. 

But these guidelines themselves aren’t clearly defined. For instance, at 28 C, workers doing “very heavy” work should spend 50 per cent to 75 per cent of an eight-hour shift resting, according to the ACGIH rules. Workers can continue “light” work with few or no breaks up to 31 C. 

The guidance offers some examples of light, moderate and heavy work (performing light “hand or arm work” like using a table saw qualifies as “light work,” for instance, as does “occasional walking,” while fast-paced walking and carrying heavy loads is “heavy work”) but these still leave room for employers’ interpretation.  

In the absence of “hard laws” to protect employees from extreme heat, workers are often at the mercy of individual employers’ goodwill, Sukdeo said. 

The ambiguity has an outsized impact on Canada’s farm workers, many of whom are migrants and non-unionized, making them particularly vulnerable to poor treatment on the job, said Santiago Escobar, a national union representative for the United Food and Commercial Workers. 

“If you are a temporary foreign worker, if you are holding a closed work permit—meaning that you don’t have labour mobility—you don’t have representation, you’re not unionized, you can complain of course, but it is very likely that you will face reprisal,” he said. 

Escobar—who helps migrant workers obtain open work permits—said he often hears from workers concerned about their safety in extreme heat. “This is an ongoing issue,” he said. “It’s very common to hear that kind of complaint.” 

The issue isn’t just about comfort on the job—there are cases of worker fatalities. Construction worker Jean-Charles Junior Wapistan died of heat stroke on the job site in Quebec in 2021. In 2001, a bakery worker in Barrie, Ont., died—another heat stroke victim—after working in a Weston-owned bakery in which temperatures were estimated to have reached 49 C. 

Tragedies like these are even more frequent in the U.S., where average temperatures in many regions are much higher than in Canada. Between 2011 to 2021, 436 workers died from heat exposure, according to the U.S. Bureau of Labor Statistics, making heat the top cause of weather-related deaths in the country.

The growing number of heat-related deaths and injuries have prompted some changes south of the border. Last month, UPS workers struck a labour agreement with their employer that includes protections from extreme heat, guaranteeing all trucks are equipped with air conditioning starting in 2024. 

At the federal level, President Joe Biden introduced legislation last month to protect workers across the country from heat stress. The proposed measures include an alert system notifying employers and employees about how to stay safe from extreme heat, and providing better access to drinking water. It also calls for heightened oversight of potentially dangerous workplaces like farms and construction sites and more enforcement of heat safety violations. 

Compared to the U.S., Canada isn’t doing much to address extreme heat on the job, said Sukdeo. “The law is constantly looking backwards,” she said. 

For that reason, she said Canada likely won’t see more robust policies for workers until temperatures and heat stress become as extreme here as in the U.S. 

“We’re gonna watch and see what happens with this new bill that’s being tabled in America,” said Sukdeo. “If that’s successful, then maybe there’ll be a Canadian response.”