What is the permissible exposure level for crystalline silica over an 8-hour shift?

The permissible exposure level (PEL) for crystalline silica over an 8-hour shift is established to protect workers from the adverse health effects associated with inhaling silica dust. The correct answer, which is 50 micrograms per cubic meter of air, reflects the standard set by OSHA specifically to mitigate risks such as silicosis, lung cancer, and other respiratory diseases linked to silica exposure.

This level is significant because it illustrates the importance of maintaining air quality standards in workplaces where silica dust is present. By adhering to the PEL, employers can ensure they are minimizing health risks to their employees effectively.

The other figures provided in the question do not align with OSHA's established limits for crystalline silica exposure. Understanding these limits reinforces the necessity for employers to monitor air quality and implement proper safety measures, including engineering controls, personal protective equipment, and training to safeguard workers' health.