Petroleum refining wastes fall under the following listed waste:

• A. F
• B. K
• C. U
• D. P

Answer: (C)

In hazardous waste classification, there are four lists that help decide how a waste should be regulated: F-list, K-list, P-list, and U-list. The U-list covers wastes that are discarded chemical products or wastes containing specific listed chemicals. Petroleum refining wastes are typically associated with solvents and chemicals that EPA has placed on the U-list, such as benzene and related solvents. When a refinery waste contains one of these listed chemicals (or is essentially a discarded listed chemical product), the whole waste is classified as U-listed. That’s why refinery wastes fall under the U category in this context.

The other lists don’t fit as neatly here: the F-list is for non-specific solvent wastes from general processes, the K-list is for wastes from specific industrial processes (more contextual to particular operations), and the P-list covers acutely toxic discarded products. The key idea is that the presence of a listed chemical in the waste makes it a U-listed hazardous waste.