Latent Effects from Radiation Exposure

DOE-HDBK-1109-97

Radiological Safety Training for Radiation-Producing (X-Ray) Devices

Student's Guide

iv. Latent Effects from Radiation Exposure.

The probability of a latent effect appearing several years after radiation exposure depends

on the amount of the dose. The higher the dose, the greater the risk of developing a health

effect. When an individual receives a large accidental exposure and the prompt effects of

that exposure have been dealt with, there still remains a concern about latent effects years

after the exposure. Although there is no unique disease associated with exposure to

radiation, there is a possibility of developing fatal cancer. The higher the accumulated

dose, the greater is the risk of health effect, based on the linear-no threshold model.

v. Risk of Developing Cancer from Low Doses.

It is not possible to absolutely quantify the risk of cancer from low doses of radiation

because the health effects cannot be distinguished from the relatively large natural cancer

rate (approximately 20 percent of Americans die from cancer). The risk of health effects

from low doses must be inferred from effects observed from high acute doses. The risk

estimates for high doses were developed through studies of Japanese atomic bomb

survivors, uranium miners, radium watch-dial painters, and radiotherapy patients. These

risk factors are applied to low doses with a reduction factor for chronic exposures.

However, below 10 rem, health effects are too small to measure. The dose limits and

administrative control levels listed in Module 101 have been established so that the risk to

workers is on a par with the risks to workers in safe industries, assuming a linear

relationship between dose and health effects. However, these are maximum values and the

ALARA principle stresses maintaining doses well below these values.

vi. Effects of Prenatal Exposure (Teratogenic Effects).

The embryo/fetus is especially sensitive to radiation. The embryo is sensitive to radiation

because of the relatively high replication activity of the cells and the large number of

nonspecialized cells.