There are now more than 2.9 million temp workers in the U.S., as the temp staffing business remains one of the fastest growing industries. But the work can sometimes be dangerous, especially if employees are not properly trained.

Univision has partnered with ProPublica to expose the sometimes deadly conditions temp workers are exposed to, often with very little, if any, training. The undercover investigation reveals the obstacles the Occupational Safety & Health Administration faces in its temp worker safety initiative.

Click the media player above to hear Univision’s Tomas Ocana in conversation with Marketplace Morning Report host David Brancaccio.