What characteristic defines a persistent waste?

A waste is considered persistent when it exhibits a high resistance to natural degradation processes. This means that it fails to biodegrade, allowing it to remain in the environment for extended periods, potentially causing long-term ecological harm and human health risks. Persistent wastes can accumulate in soil, water, and biota, leading to bioaccumulation and biomagnification through food chains.

The other characteristics mentioned, such as rapid degradation, being hazardous only when burned, or being restricted to liquid form, do not accurately capture the defining aspect of persistence. Wastes can be persistent regardless of their physical state—solid, liquid, or gas—and not all persistent wastes are only hazardous when subjected to burning. Thus, the focus on the failure to biodegrade accurately reflects the fundamental nature of persistent wastes.