Heat protection will be one of the key issues in the upcoming Teamsters negotiations at UPS for the biggest union contract in North America, which covers the majority of UPS’s 350,000 workers. The current contract expires next year.

The Teamsters issued a public letter last week outlining a series of steps it says UPS should take immediately to improve the safety of its drivers in excessive heat. They include providing fans in every truck, cooling neck towels, consistent supplies of water and ice, more breathable uniforms, and hiring more drivers to reduce workload.

Sean M. O’Brien, Teamsters general president, says, “By refusing to implement these safety measures, the company is literally sending drivers out to die in the heat.”

In New York City, the local Teamsters union held a rally after four UPS employees in Long Island and Manhattan went to emergency rooms in two days. Local union president Vincent Perrone announced he was taking the unusual step of pulling all union representatives from weekly safety meetings with the company.

“If and when the Company decides to take the safety of our people seriously, I will consider reinstating the committee,” he wrote in a public letter.

As Oklahoma suffered weeks of record 100-plus degree days, a group of UPS drivers distributed thermometers to collect temperature readings from the front and back of several dozen trucks. On one 103-degree afternoon, they logged 12 different readings between 110 and 127 degrees, according to an NBC review of their data.