Final answer:
The agency responsible for approving respirators for workplace exposure, alongside the Mine Safety and Health Administration, is the Occupational Safety and Health Administration (OSHA).
Step-by-step explanation:
Respirators must be approved for the contaminant or situation to which the employee is exposed by the Mine Safety and Health Administration of the Department of Labor, and by the Occupational Safety and Health Administration (OSHA). OSHA is responsible for ensuring safe and healthful working conditions by setting and enforcing standards, including those related to the use of personal protective equipment like respirators. The agency's regulations are designed to protect workers from a wide range of serious hazards, including exposure to harmful chemicals, and require employers to provide respirators or other safety equipment when necessary. Therefore, the correct answer is 2) Occupational Safety and Health Administration.