The action wasn’t the only thing sizzling during the opening match of the Women’s World Cup on Saturday between Canada and China. So was the controversial artificial turf that composed the pitch in Edmonton, Canada. An hour before kickoff at 6 p.m. EDT, the fake grass measured 120 degrees, or 49 degrees Celsius, according to a Fox Sports sideline reporter.

That’s almost unsafe to play on, according to a study cited by the Las Vegas Sun in 2009. The research, partly funded by the city of Las Vegas, found artificial turf above 122 degrees is considered unsafe for sustained athletic use and that, depending on the air temperature, turf can get as hot as 180 degrees.

“This was a temperature where if you put your hand down on it, you could only hold it for five seconds or so before it would burn,” Dale Devitt, director of the Center for Urban Water Conservation at the University of Nevada Las Vegas told the Sun. He conducted the study along with the Desert Research Institute’s Division of Hydrological Sciences.

“During the summer months, the artificial turf is not suitable for play during the day,” Devitt said, referring to Vegas’s average high temperatures that can reach over 100 degrees between June and August.

Canada, luckily, won’t have to worry about air temperatures that high, but that doesn’t mean the sun won’t make the artificial turf that covers all six Canadian venues unpleasant.

For example, the air temperature in Edmonton measured just 75 degrees on Saturday, but when plastic and rubber sits directly beneath the sun for hours, it collects more heat. Players won’t burn themselves on the artificial grounds, but the heat radiating from beneath them could cause them to tire quicker.

Players have already complained about FIFA and the Canadian Soccer Association’s decision to install fake grass for the 2015 tournament, with some, including several members of Team USA, even taking the issue to court. The women eventually withdrew their lawsuit from the Ontario Human Right Tribunal because FIFA wouldn’t budge, although the world soccer governing body did promise never to use artificial turf at the women’s World Cup again.

The women, however, still see the decision to use fake grass at this tournament as gender discrimination. Artificial turf has never been used in a men’s World Cup and the men’s tournaments scheduled for 2018 and 2022 were always going to be played on real grass.

“Between men and women … this is not equal,” Team USA star Sydney Leroux said in a recent video interview with Vice Sports. “For us to be playing the biggest tournament for women’s soccer on artificial grass is unacceptable. The game is completely different. It’s fake. So you don’t know how it’s gonna bounce. You don’t know how the ball is gonna run. It’s terrible for your body. The constant pounding. You’re running pretty much on cement. … We’re the guinea pigs.”