Which measure represents a health risk due to radiation exposure?

The rem (radiation equivalent man) is a metric that specifically quantifies the biological effect of ionizing radiation on human health. This unit takes into account not only the amount of radiation absorbed but also the potential biological damage it can cause, reflecting both the dose received and the type of radiation involved.

The rem is crucial in assessing health risks from radiation exposure as it helps determine safe exposure limits and assess the potential for radiation-induced health effects, such as cancer or other long-term consequences. It is used in various fields, including medicine, environmental science, and nuclear safety, to ensure that exposure levels remain within acceptable and safe standards.

In contrast, the Parker Unit, infectious dose, and lethal concentration pertain to other contexts of health risks. The Parker Unit is not a recognized standard for measuring radiation exposure. Infectious dose relates to the quantity of pathogens required to cause disease rather than radiation. Lethal concentration generally refers to the concentration of a toxic substance in the air or water needed to cause death, which does not directly address radiation exposure.