Michael Grabell

At the time of their accidents, Jeremy Lewis was 27, Josh Potter 25. The men lived within 75 miles of each other. Both were married with two children about the same age. Both even had tattoos of their children’s names.

The head of the U.S. Senate's workplace safety subcommittee has asked the Occupational Safety and Health Administration to explain its handling of the death a temp worker who suffocated under a pile of sugar at a Pennsylvania plant. The details of OSHA's investigation were reported Sunday by ProPublica and Univision.

For nearly six years, Limber Herrera has toiled as a temp worker doing the same work for the same company in Mira Loma, Calif. About 40 hours a week, he unloads shipping containers for NFI—one of the largest freight distribution firms in America—moving goods that will eventually stock the shelves of Walmart and Sam’s Club.

It’s 4:18 a.m. and the strip mall is deserted. But tucked in back, next to a closed-down video store, an employment agency is already filling up. Rosa Ramirez walks in, as she has done nearly every morning for the past six months. She signs in and sits down in one of the 100 or so blue plastic chairs that fill the office.

Since the Rana Plaza building collapse killed more than 1,100 people in April, retailers have faced mounting pressure to improve safety at Bangladesh garment factories and to sever ties with manufacturers that don't measure up.