Which organization was established to assure safe working conditions for workers?

The Occupational Safety and Health Administration (OSHA) was established specifically to ensure safe working conditions for workers in the United States. OSHA's primary purpose is to prevent workplace injuries and illnesses by setting and enforcing safety standards, as well as providing training, outreach, education, and assistance. It plays a crucial role in promoting health and safety in various industries, including those involving wastewater treatment, where workers may be exposed to hazardous materials and conditions.

In contrast, other organizations mentioned do not focus primarily on workplace safety. The Environmental Protection Agency (EPA) is tasked with protecting human health and the environment, while the National Labor Relations Board (NLRB) deals with labor relations and the rights of employees to organize and bargain collectively. The Federal Emergency Management Agency (FEMA) is involved in managing and responding to emergencies and disasters, rather than directly ensuring workplace safety. Therefore, OSHA uniquely fulfills the mission of assuring safe working conditions for workers.