To me, it's a matter of escalation.
The first communication should be verbal and it should be directed at exactly those people responsible or affected, and it should be, "Guys, this ain't safe. I have some real concerns here."
The second communication should be formalizing the observation in a Near Miss or other incident report, if such an avenue exists in the company.
If no action occurs after that, and you still have a concern, email all concerned with a copy to your boss and HR; be prepared to be fired at this point.
If still no action, quit, and don't mince words during your exit interview.
People are either prepared to "live or die by the sword", or they're not. There's nothing wrong with those people who aren't willing to take things to difficult levels or ultimatums for fear of reprisal, family concerns, fear of job loss, etc., but to me, my advice would be: don't start fights that you aren't prepared to finish, even if the outcome for you, personally, sucks.
Play the scenario out:
"This situation is dangerous and it bothers me."
"If you complain about it, it will cost you your job."
Response "A":
"OK, I guess it doesn't bother me that much."
Response "B":
"I don't give a crap, it bugs me and I plan to make my concerns known."
Be the guy or gal who goes with Response "B".