Which organization developed the placard and label system for hazardous materials?

The correct choice is the one that highlights the collaborative effort between the United Nations and the United States Department of Transportation in developing the placard and label system for hazardous materials. This system is essential for ensuring safety and compliance in the transportation and storage of hazardous substances.

The United Nations has established international regulations for the classification and labeling of chemicals, which aim to promote safety and protection across borders. The Department of Transportation plays a crucial role in implementing these regulations in the U.S. to ensure that dangerous goods are appropriately labeled and that proper placarding is conducted during transport.

In contrast, the other organizations listed have their specific focuses: the Federal Aviation Administration primarily deals with civil aviation safety; the Environmental Protection Agency monitors environmental issues and regulations; and the Occupational Safety and Health Administration oversees workplace safety regulations, which do not specifically include the development of the hazardous materials placard and label system. Therefore, while each plays a significant role in their respective areas, the partnership between the United Nations and the Department of Transportation is pivotal for the hazardous materials labeling system.