Final answer:
Radioactive placards must be displayed on a vehicle carrying Class 7 materials but are prohibited when no Class 7 materials are on the vehicle. These regulations ensure safety and are mandated by both the USDOT and the EPA The correct option is C.
Step-by-step explanation:
Radioactive placards are used to indicate the presence of Class 7 materials, which are radioactive substances. These placards must be displayed on transport vehicles when carrying such materials to notify and ensure the safety of the public and any emergency response personnel in the event of an incident. According to transport regulations, radioactive placards are prohibited from being displayed on a vehicle when there is not any Class 7 materials on the transport vehicle. The display of these placards is governed by strict regulations that align with both the United States Department of Transportation hazardous materials regulations and the Environmental Protection Agency's hazardous waste regulations. These standards are important because of the health risks associated with radioactive materials, such as those that could arise from homes built with cinder blocks containing uranium mine tailings, potentially releasing hazardous radiations like radon gas.
It is crucial to ensure that the placards are used appropriately. They are not needed for onsite shipments where the materials are not entering public transport routes. Additionally, for international shipments or when the shipment involves mixed hazards, the regulations still require placards, though there may be additional or modified requirements based on the international destination's regulations or the specifics of the materials being transported. In all cases, proper training and handling procedures are essential to minimize the risks associated with radioactive materials, whether being transported or used within facilities such as a nuclear medicine department in a hospital.