Which organizations approve respirators for safety use in pesticide applications?

The correct answer is based on the roles that the organizations play in the regulation and approval of respiratory protective devices, particularly in the context of pesticide applications. The National Institute for Occupational Safety and Health (NIOSH) is responsible for testing and certifying respirators to ensure they meet required safety standards. This certification is crucial for ensuring that the respirators effectively protect users from harmful substances, including pesticides.

The Mine Safety and Health Administration (MSHA) also plays a role in ensuring safety in hazardous environments, particularly in mining. Though their primary focus is not on pesticide applications, they are involved in the oversight of safety equipment used in various industrial applications. Therefore, the combination of NIOSH's certification and MSHA's focus on workplace safety makes this the correct choice regarding which organizations are involved in the approval of respirators for safe use in situations like pesticide application.

The other organizations mentioned in the other choices either do not focus directly on respirator approval or have different safety interests that do not align with the specific context of pesticide applications and respirator use. This distinctive focus is what solidifies the correct answer as the best choice.