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11 October 2008

Answer to Question #187 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Food and the Human Body

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

Can you measure the amount of radiation that is already in your body?

Radiation can be measured by using sensitive detectors in a whole body counter (you'll find pictures on the National Calibration Reference Centre for Bioassay and In Vivo Monitoring Web site). These detectors can measure the gamma rays emitted by radioactive materials that get into or onto the body. Different radioactive materials will give off gamma rays of different energies, which is one technique to identify the material. Other types of radioactive decay (beta and alpha) cannot be detected in this way, but fortunately gamma rays often accompany them so most can be detected. The instrumentation is very sensitive so that the detection limits are well below levels that have a health significance. For example, a whole body counter can easily measure the amount of radioactive potassium that is naturally occurring (0.0117 percent) and in every person, animal, and plant. Most radioactive materials that get into the body also leave. The speed at which they leave will depend on their physical and chemical form.

Dr. Gary H. Kramer
Head, Human Monitoring Laboratory
Canadian National Calibration Reference Centre for In-Vivo Monitoring

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