It is not in an employer's best interests to injure or incapacitate its workers, but even still, employers cannot always be expected to look out for every possible source of injury at the workplace, especially when it comes to jobs that are inherently dangerous. This is why OSHA exists. OSHA is a federal administration that protects workers and seeks to ensure that the health and safety of employees is considered at all times.
One of the best ways to avoid unsafe working conditions is to report the conditions to OSHA, at which point measures will likely be taken to reduce or eliminate the dangers. This can significantly reduce the risk of workplace accidents and can even make work more efficient since employees would no longer have to exercise extreme care to avoid injury. Of course depending on the nature of the unsafe condition, there may not be time to report it to OSHA.
In the event that a safety hazard poses a threat so imminent that you cannot report it to your employer or to OSHA, you can legally refuse to work. This may sound surprising, but the truth is that if there is reasonable cause to believe that the hazard poses an immediate and significant threat, and your employer will not fix the issue, and if you have no alternative way of completing the functions of your job, you can simply not work. Additionally, you have the right to continue refusing to work until the danger is eliminated or found not to exist.
Your employer will likely look out for your best interests whenever possible, and there are federal guidelines designed to make workplaces safe, but the truth is that the only person who can truly understand the potential dangers of a workplace scenario is you. Fortunately, you are given enough legal leeway to make a judgement call for your own safety. If you do find yourself injured in a workplace accident, consider meeting with an attorney. You could be entitled to benefits from workers' compensation.