Which one of the following is least likely to occur in the US?

Cadmium poisoning is considered the least likely to occur in the U.S. compared to the other listed options. In industrial and environmental contexts, cadmium exposure can arise from sources like battery manufacturing, mining, and the burning of fossil fuels; however, stringent regulations and improved industrial practices have significantly reduced cadmium's prevalence in the environment.

In contrast, households and communities may encounter lead poisoning more frequently, often from lead-based paints in older homes or plumbing materials, which remain a major public health concern. Similarly, mercuric poisoning can still occur, especially in certain populations exposed to contaminated fish, and PCB (polychlorinated biphenyl) poisoning is associated with past industrial practices. PCBs have been widely banned, but their historical presence can still lead to contamination in the environment.

Thus, cadmium represents a lower risk factor in the contemporary context of the U.S., reflecting both the historical usage patterns of these toxic substances and current public health efforts aimed at minimizing exposure to harmful environmental contaminants.