Which guideline for limitation of exposures refers to airborne concentrations of substances and represents conditions under which it is believed that nearly all workers may be unaffected?

OSHA Exposure limit.

Explanation:

The topic comes under occupational health hazards as the prolonged exposure to airborne concentrations of substances in the environment which affects nearly all the workers. The mass of particular substances and their concentration increases the risk of various side effects on the body of the work as well as on their physiological capacity to work.