Your Body Is Radioactive ― Does It Harm You?

Mention radiation, and most people immediately think about nuclear power plants or nuclear accidents. But there are a lot of natural sources of radiation that we're all exposed to every day. Radiation is a part of your life. Most of the materials we encounter daily contain radioactive elements. This adds up to a dose of about 620 mrem (6.2 mSv) of radiation each year for the average American. This is roughly equivalent to 10 x-rays of the abdomen.

In most cases, humans do not emit other forms of radiation rather than thermal radiation, but we all have several other naturally occurring radionuclides in our bodies, and these radionuclides are 238 U, 234 U, 232 Th, 210 Po, 210 Pb, 40 K, 226 Ra, 228 Ra, 14 C, 7 Be, 22 Na. 

Some of these elements are critical for the proper functioning of several organs/tissues. Radioactive elements enter the body through inhalation of air through breathing and through ingestion of food. All food products are slightly radioactive due to their carbon 14 and potassium 40 content. For example, Brazil nuts and bananas, contain higher amounts of radioactive elements. But the amounts are too small to be noticeable or to have an effect on their health. These substances are absorbed by our bodies, our tissues, organs, and bones, and are constantly replenished by ingestion and inhalation. 

The concentration of gamma-emitting radionuclides, except 40 K, in humans is so small that none of them can be detected using normal full-body counters available to measure any intake of radionuclides. This radionuclide has been around since the birth of the earth and is present as a small fraction of all potassium in nature.

The concentration of 40K in the body is quite high, as it is ingested in many of the foods we eat and is a critical element for the proper functioning of the human body; it is present in almost all of the body's tissues. The amount of the radioactive isotope 40K in a person of 70 kg is approximately 5,000 Bq.

The annual effective dose of radiation due to the 40 K body content is 0.165 mSv, and 0.12 mSv due to the Uranium and Thorium radionuclides series. Whereas annual effective doses of 14 C, 22 Na, 3 H and 7 Be radiation are 0.012 mSv, 0.15 μSv, 0.01 μSv and 0.03 μSv, respectively. 

The total annual effective dose of different natural radionuclides present in our human body is approximately 0.3 mSv, which's less than the annual effective dose of 1 mSv noted to the public by the International Commission on Radiological Protection (ICRP) from the ingestion of contaminated food. So, you don't need to worry about that.

The average person in the United States can receive about 620 mrem (6.2 mSv) per year from all radiation sources. This includes, on average, about 310 mrem (3.1 mSv) from natural sources and about 310 mrem (3.1 mSv) from man-made sources and applications. An exposure greater than 20 mSv is considered high, while exposures greater than 3 mSv to 20 mSv are considered moderate. 

But, very high doses of radiation or acute exposure over a short period of time can cause symptoms such as nausea and vomiting within hours and can sometimes lead to death over the next few days or weeks. This is known as acute radiation syndrome.