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05 September 2008

Answer to Question #322 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — In the Body

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

What is the ⁴⁰K and ¹⁴C inventory in the typical human body? I would like it in Bq per kg by sex. Thanks.

Potassium-40 content of the body can be obtained from its natural abundance of 0.0117% of potassium and calculating the specific activity of natural potassium (30.5 Bg/g) using the half life (1.28 x 10⁹ y). The potassium content of the body is 0.2%, so for a 70 kg man the amount of ⁴⁰K will be about 4.26 kBq. ¹⁴C content of the body is based on the fact that one ¹⁴C atom exists in nature for every 1,000,000,000,000 ¹²C atoms in living material. Using a half life of 5730 y, one obtains a specific activity of 0.19Bq/g of carbon. As carbon is 23 percent of the body weight, the body content of ¹⁴C for a 70 kg man would be about 3.08 kBq.I don't have the breakdown of body content by gender.

Gary Kramer, PhD

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