Which agency has developed an app for monitoring noise levels?

The correct answer, which identifies the agency that has developed an app for monitoring noise levels, is NIOSH, the National Institute for Occupational Safety and Health. NIOSH is a federal agency responsible for conducting research and making recommendations to prevent work-related injuries and illnesses. Specifically, NIOSH has developed tools and resources to help employers and employees monitor workplace conditions, including noise levels which can impact hearing health.

The application created by NIOSH is designed to assist users in measuring sound levels, informing them when noise exceeds safe levels, and serving as a resource for individuals and employers to implement appropriate hearing conservation strategies. This focus aligns with NIOSH's mission to enhance worker safety and health, as exposure to high noise levels can lead to hearing loss and other health issues.

The other agencies listed, while also important in various domains of public health and safety, do not specifically focus on noise monitoring through a dedicated application. OSHA (Occupational Safety and Health Administration) enforces workplace safety and regulations but does not directly develop apps for noise monitoring. The EPA (Environmental Protection Agency) is more concerned with environmental health and protection, and the FDA (Food and Drug Administration) deals primarily with food safety and pharmaceuticals, which do not include workplace noise monitoring.