Radiation Exposure

Human radiation exposure is measured by the amount of radioactive energy deposited in a body's tissue in rad units (or in the international unit, a gray). Since different tissues have different mass and molecular structure, the same radioactive source of energy will, therefore, cause different rad doses. Some radioactive materials deposit in specific organs. Iodine-131, for example, deposits in the thyroid gland where it can cause thyroid cancer and hypothyroidism. Other radioactive materials like Cesium-137 are more generalized and are absorbed into the body's soft tissues where they can cause a variety of cancers.1

Data in the table and graph below show the 1945 levels of exposure to Iodine-131 from drinking milk. The data is organized by gender for various age groups and for exposure Zone 1, closest to Hanford, and for Zone 2, further from the site. The ages represent the low end of an age group. For example, "0" represents ages 0 to 1; "1" represents ages 1 to 5, and so on. The exposure values are the mid range value for each age group.

1945 Iodine-131 Exposure from Milk

To Start You Thinking

1) Were boys or girls more prone to exposure from Iodine-131?

2) Describe the relationship between age and exposure to Iodine-131. What factors do you suppose contribute to this relationship?

3) Mathematically we say that there is an inverse relationship between Age and Exposure to Iodine-131. Develop an equation that models the relationship for Zone 1 males; for Zone 1 females.

4) Considering the relationships you see discuss the risk from exposure to Iodine-131 for a 38 year old mother who lived close to Hanford in 1945 and her 3 year old son and fourteen year old daughter.


1"Radiation Protection: Health Effects", United States Environmental Protection Agency, 2011.

data from The Technical Steering Panel of the Hanford Environmental Dose Reconstruction Project, Summary: Radiation Dose Estimates from Hanford Radioactive Material Releases to the Air and the Columbia River, April 21,1994, p 3

Last modified in May, 2017 by Rick Thomas