The word friable would most likely apply to which of the following?

The term "friable" refers to materials that can be easily crumbled or reduced to powder, particularly when dry. In the context of hazardous materials, the relevance of this term is crucial for understanding health risks and safe handling practices. Asbestos is a fibrous mineral that poses serious health risks when its fibers become airborne, which can happen if the material is damaged, disturbed, or deteriorating. Friable asbestos can easily release harmful fibers into the air, making it particularly dangerous.

When considering the other options, while lead-based paint can deteriorate and produce dust that may be harmful if ingested or inhaled, it is not categorized as friable in the same way as asbestos. Radon gas is a naturally occurring radioactive gas that is not a material that can be categorized as friable. A Superfund site is a contaminated area that requires long-term clean-up of hazardous substances, but it does not inherently imply the presence of friable materials. Thus, asbestos stands out as the material most closely associated with the term "friable."