Other minor contributors
Other contributors to dose include consumer products, industrial sources, and
atmospheric testing of nuclear weapons.
3. Average annual dose
The average annual total effective dose equivalent to the general population (non-
smokers) from naturally occurring and manmade sources is about 360 mrem.
B. Effects of Radiation on Cells
The human body is made up of many organ systems. Each system is made up of tissues.
Specialized cells make up tissues. Ionizing radiation can potentially affect the normal
function of cells.
1. Biological effects begin with the ionization of atoms
a. The method by which radiation causes damage to human cells is by ionization of
atoms in the cells. Atoms make up the cells that make up the tissues of the body.
Any potential radiation damage begins with damage to atoms.
b. A cell is made up of two principal parts, the body of the cell and the nucleus. The
nucleus is like the brain of the cell.
c. When ionizing radiation hits a cell, it may strike a vital part of the cell like the
nucleus or a less vital part of the cell, like the cytoplasm.
2. Cell sensitivity
Some cells are more sensitive than others to environmental factors such as viruses,
toxins, and ionizing radiation.
a. Actively dividing and non-specialized cells
1) Cells in our bodies that are actively dividing are more sensitive to ionizing
2) Cells that are rapidly dividing include blood-forming cells, the cells that line our
intestinal tract, hair follicles, and cells that form sperm.
b. Less actively dividing and more specialized cells
Cells that divide at a slower rate or are more specialized (such as brain cells or
muscle cells) are not as sensitive to damage by ionizing radiation.
3. Possible effects of radiation on cells