Question

Recall rem = rad x Q

Radiation weighting factor (Q): the ability to transfer energy to the body

1 for photons

1 for electrons

2 for protons

20 for alpha particles, fission fragments, and heavy ions

2 to 20 for neutrons, depending on the energy level

Suppose two people are exposed to equal doses of radiation (equal number of rads) inside their bodies. Suppose that the first person is exposed to alpha radiation, while the second person is exposed to protons. How many times worse is the biological risk for the first person than the second as a result of radiation weighting?

Answer 1

Use rem = rad × Q.

For alphas Q = 20, for protons Q = 2. So the ratio is 20 / 2 = 10.

Thus, for the same absorbed dose (rads), the person exposed to alpha radiation has about 10× the biological risk (rem) of the person exposed to protons.

(Note: this uses ICRP-style radiation weighting factors — they’re approximate and assume similar distribution and biological context.)