During a summer that has already shattered temperature records, the 340,000 drivers, dispatchers, and warehouse workers currently in contract negotiations with UPS — the United States’ largest unionized employer — have made climate change and extreme heat a headline labor issue. And if they don’t secure a contract by July 31, they are poised to initiate the largest single-employer strike in U.S. history.

On summer days, the back of a delivery truck can exceed 120 degrees Fahrenheit. When Viviana Gonzalez, a package delivery driver for United Postal Service in Los Angeles, pulls open the back of her truck, she often thinks: “Am I going to pass out back here? Will anybody find out that I’m here in the back of the truck?”

Gonzalez is all too aware of how dangerous her job can be. Since 2015, UPS has reported at least 143 heat-related injuries to the federal Occupational Safety and Health Administration. Last year, one of her co-workers, Esteban Chavez, died of heat stroke in his delivery truck after delivering his last parcel. “I’m a single mom,” said Gonzalez, “and being able to provide for my son means I have to suck it up.”

While climate change is making summers hotter and even more dangerous for delivery workers, Moe Nouhaili, a UPS driver in Las Vegas, told the Guardian that it’s the working conditions that make the heat so deadly. “It’s how they’re making us work, expecting us to meet these unrealistic productivity numbers even through the weather,” he said.

UPS often requires drivers and warehouse employees to work six days a week and more than 12 hours a day in the heat, and the company measures worker productivity by surveillance cameras and sensors inside trucks. Drivers say these tactics make it harder to take breaks. “The same amount of work that would be done in, say, 30 routes is now being forced to be done in 20 or 25,” said Nouhaili. “Less people get more work done.”

An increasing portion of the work is also done by part-time drivers who are paid less than full-time employees, as well as gig workers who often need to take on multiple jobs to make ends meet.

Read the full article about labor rights and climate change by Tushar Khurana at Grist.