I just read a study that found a strong mediating influence of co-worker voice on the relationship between organizational support for safety and the likelihood a worker will speak out about safety.
Basically, they found that even when a company visibly supports safety, workers only speak out when they see a hazard if their coworkers also support safety.
The implication is that all of the efforts companies make to support safety are minimized if some jerk in the workplace makes fun of you for trying to be safe. Although the study couldn't look at every variable, I bet that this effect is subtle. If a worker is unsure how his/her coworkers feel, he/she still will hesitate before speaking out. Only when the company visibly supports safety and the coworkers buy in to it will you get people speaking out when they see a hazard. This is sad, and reminds me of recess in junior high. But its the way our world works I guess.