We are exposed every day to ionizing radiation of natural origin (radon, cosmic radiation, etc.) and artificial (mainly of medical origin). This exposure varies enormously depending on our way of life. At what dose should you be concerned and what are the long-term health effects?
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The legal limit for exposure to radioactivity in France is 1 millisievert (mSv) per year for the whole body, excluding medical and natural exposures. The equivalent dose for the lens is 15 mSv/year and for the skin 50 mSv/year. This extremely low dose is to be compared to the natural radioactivity that we receive each year (2.9 mSv/year) and from medical examinations (a scanner is equivalent to an effective dose of 15 mSv).
Radioactivity due to radon: what dose is dangerous?
The main source of long-term exposure is radon, which comes from the ground, building materials construction and the building. There is no regulatory limit in France concerning the house but epidemiological studies show an increased risk of Cancer from continuous exposure for 30 years above 200 Becquerel per cubic meter (Bq/m³). IRSN thus estimates that radon is the second leading cause of death by lung cancer after tobacco.
Radioactivity: what are the alert thresholds?
For the general public, sheltering is planned from a forecast exposure of 10 mSv/year and evacuation from 50 mSv/year. In the event of an accident at a nuclear reactora distribution of iodine tablets is organized in order to protect the thyroid against the effects of the radioactive iodine released during theaccident.
Radioactivity: what dose has health effects?
It is estimated that the increase in the risk of cancer is 0.005% (50 cases per million people) at an exposure of 1 mSv/year (compared to the probability of death from cancer in France which is around 25%). Since the studies on low doses are based on epidemiological data, it is however difficult to be certain about the origin of these possible cancers. According to the International Commission on Radiological Protection (ICRP), no long-term health effects have been proven below a dose annual of 100 mSv/year. From 1,000 mSv/year (1 Gray), on the other hand, radioactivity has a immediate effect on health and involves a vital risk for the person in the weeks and months that follow:
- from 1 Gy: redness appears on the skin and blood cells are affected;
- from 4 Gy: the lens is damaged;
- from 5 Gy: the gonads (sex cells) undergo irreversible changes in humans;
- from 10 Gy: impairment of the digestive tract;
- from 40 Gy: reaching the central nervous system.
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