Which of the following decay products is known for its high radiotoxicity?

Polonium-218 is recognized for its high radiotoxicity primarily due to its alpha-emitting properties, which are highly damaging to biological tissues when ingested or inhaled. The alpha particles emitted by Polonium-218 can cause significant harm to cellular structures, leading to severe biological effects even at very low exposure levels.

As a heavy metal, Polonium-218 tends to accumulate in the body, increasing its potential for harm. This radiotoxicity is a critical factor in understanding the health risks associated with radioactive materials and helps in the assessment of safety protocols for handling such isotopes.

Other isotopes like Lead-214 and Bismuth-214, while they are indeed part of the decay chain of Radon-222 and also emit radiation, do not exhibit the same level of radiotoxicity as Polonium-218. Radium-226, although hazardous, is primarily known for long-term health concerns associated with its decay products rather than immediate radiotoxic effects. The unique harmful nature of Polonium-218 makes it particularly significant in discussions of radiotoxicity.