Answer to Question #4004 Submitted to "Ask the Experts"

Category: Industrial Radiation — Industrial Applications

The following question was answered by an expert in the appropriate field:


How is radiation used to sterilize medical instruments?


Sterilization, the killing of bacteria (or any types of cells), on medical instruments is primarily achieved by the radiation causing severe damage to the cell's components and to the cell's chromosomes, specifically the DNA. "Severe damage" to DNA is multiple breaks in the long DNA ladder-like structure. Radiation (for example, gamma rays, x rays, or beta and alpha radiation) has enough energy to ionize atoms and molecules; that is, it can create charged particles and free radicals. In cells, the water can be ionized to form free radicals, somewhat like H-plus (H+) and OH-minus (OH-) radicals found in acids (for example H+Cl-) and bases (for example, Na+OH-). The free radicals made inside a cell's nucleus can cause damage to the cell's components and breaks in the DNA structure (the radiation may also directly cause ionizing breaks in the DNA's chemical chain). If enough damage is done to the cell's DNA, which acts as the cell's control mechanism, the cell cannot function properly or reproduce and the result is cell death (sterilization).

Radiation is used to sterilize medical instruments by first sealing a clean, but not bacteria-free, instrument in an air-tight bag. The bag and instrument are then placed in a very large field of radiation that can penetrate the bag—for example, gamma radiation, x rays, or high-energy electrons. These ionizing radiations can kill the bacteria (cells); and the air-tight bag will keep the instrument sterile until the bag is opened in the medical facility.

Look at the E-Beam Services, Inc., website for more information.

Hope this helps and thanks for your question.

John P. Hageman, MS, CHP

Answer posted on 18 October 2004. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.