Answer to Question #404 Submitted to "Ask the Experts"

What you've heard is not true. Nerve cells are very specialized cells and do not undergo cell division. Therefore, nerve cells are not very sensitive to radiation. Keep in mind, however, that the skin is a complex organ made up of many different types of cells, including nerve cells, and structures such as hair follicles, glands, and blood vessels. When the skin receives a high dose of radiation the primary damage occurs to hair follicles, basal (dividing) cells of the outer skin layer, and small blood vessels. At radiation doses of about 300 rads (300,000 millirads) hair loss will occur in the irradiated skin. Note: for comparison an average chest x ray delivers about 10 millirads. At 600 rads (600,000 millirads) erythema, or skin reddening, will occur. At even higher doses destruction of the skin occurs due to direct skin cell death, loss of basal cells, or reduced blood flow due to destruction of small blood vessels. Pain is associated with loss of the integrity of the skin because nerves can become exposed to the air, die due to loss of blood flow, or be affected by infection of the damaged skin. Gen Roessler, Ph.D. HPS Web Site Editor

Because adult brain cells (called neurons) do not divide, they are less radiation sensitive than dividing cells such as those in the bone marrow or gastrointestinal tract. However, high-dose radiation therapy (for the treatment of cancer) can cause damage to the brain and spinal cord. Radiation therapists plan radiation treatments to avoid high-dose exposure of healthy central nervous system structures so as to prevent neurological damage. Interestingly, the central nervous system in the developing fetus is very sensitive to radiation because these cells do divide. Studies of individuals who were exposed prior to birth to atomic bomb radiation in Japan indicate that IQ may be affected. Kenneth L. Mossman, Ph.D.