Wellness

Radioactivity: nuclear medicine, the first source of exposure

The entire French population is exposed to ionizing radiation. There are two origins to this exposure, one is natural in origin and the other originates from human activities. According to the Institute for Radioprotection and Nuclear Safety (IRSN), the exposure of the French population is estimated, on average, at 3.7 mSv per person and per year, but this exposure presents great individual variability, in particular according to location. place of residence and the number of radiological examinations received. The average natural and artificial radiation dose can thus vary by a factor of 2 to 5.

The exposure of the population to ionizing radiation of natural origin has always resulted from the presence of radionuclides of terrestrial origin in the environment, from the emanation of radon from the subsoil and from exposure to cosmic radiation. Exposure to natural radioactivity represents on average approximately 65% ​​of total annual exposure. For the remaining 35%, it comes from human activities related to industrial nuclear, military but especially medical.

To see more clearly, here is the distribution of sources of natural and artificial radioactivity in France/year (IRSN estimate):

– for approximately 1 mSv/year: natural radioactivity (excluding radon), due for 0.5 mSv/year to radiation of telluric origin, 0.3 mSv/year for cosmic radiation and 0.2 mSv/year due to food and drinking water.

– for approximately 1.4 mSv/year, radon with a very large variation linked to the geological characteristics of the land and the buildings themselves. In areas highly exposed to this radioactive gas, periodic measurements must be taken in educational or health and social establishments, in workplaces and, from 2014, in residential buildings.

– for about 1.3 mSv/year, medical treatments with a clear upward trend. From 0.8 mSv per year in 2002, we rose to 1.3 mSv per year in 2007. This worrying increase is due to the increase in the doses delivered in the context of radiological examinations for diagnostic purposes.

– for 0.03 mSv/year, the other sources of artificial exposure: former military air nuclear tests, accidents occurring at facilities, releases from nuclear facilities, Chernobyl.

The effects of radiation on health

The effects of ionizing radiation on the body vary according to the dose received and various factors: the source (intensity, nature, energy, etc.), the mode of exposure (time, flow rate, etc.) and the target (tissues or organs). affected, age of the individual, etc.).

There are two types of biological effects. Immediate effects, which are due to strong irradiation by ionizing radiation which cause immediate effects on living organisms such as, for example, more or less significant burns, erythema, radiodermatitis, radionecrosis and cataracts. Depending on the dose and the organ affected, the time to onset of symptoms varies from a few hours to several months.

The second type of effect is said to be long-term and is due to exposure to more or less high doses of ionizing radiation that can have long-term effects in the form of cancers and leukaemias. The likelihood of the effect occurring increases with dose. The time to onset after exposure is several years.

The problem is that a radiation-induced pathology has no particular signature, there is no biological marker to differentiate, for example, lung cancer due to tobacco from lung cancer linked to radioactivity.

In general, when the tissues are not too affected, these effects are reversible and the affected areas can heal. But, in the case of very strong irradiation, too many cells are destroyed, leading to the destruction of the irradiated tissues or organs, which may require the amputation of a limb or, in the event of damage to the systems vital, can lead to death.

A special case, Radon

The International Commission on Radiological Protection of the WHO, UNSCEAR published in its latest report (2013) the evaluation of the risk of lung cancer due to radon, a radioactive gas of natural origin (descendant of uranium and thorium). This gas, likely to accumulate in buildings, is the subject of specific modelling, based on the observation of epidemiological data among mine workers. It concludes that the relative risk linked to exposure to radon, for the public, is of the same order as that linked to passive smoking, ie an estimate which predicts between 5,000 and 6,000 deaths per year. Radon is present in various ways in the territory, there are regions where, due to the geological structure, the concentration in buildings, cellars, houses is greater. This is the case in Brittany, because of the granite, in Haute Savoie, in the central region or in Corsica. The only response to exposure to this gas is the daily ventilation of homes and for the highest concentrations, the installation of ventilation.

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By dint of scanners, the risk of cancer

Medical exposures to ionizing radiation (particularly those resulting from computed tomography, tomography and interventional radiology examinations) represent the largest share of man-made exposures in developed countries. They are constantly increasing in most countries. CT scans contribute more to receiving radiation doses than conventional radiological procedures. The CT procedures delivering the most doses are the

abdominal-pelvic and thoracic scans. By way of example, at age 50, the average individual doses attributable to conventional radiology and CT examinations are respectively equal to 0.5 and 1 mSv per year in women and 0.3 and 1 mSv per year in men. ‘man.

It is crucial for health to reduce the doses related to medical imaging, especially when alternative techniques can be used, because the multiplication of the most irradiating examinations, for the same person, could lead to reaching the effective dose value of 100 mSv, above which epidemiological studies have shown that the probability of developing radiation-induced cancer becomes certain.

Radiation hypersensitivity 10% of population at risk

The effects of ionizing radiation on human health vary from individual to individual. For example, the same dose does not have the same effect depending on whether it is received by a growing child or by an adult. In this context, radiation protection specialists are increasingly alarmed by the reality of individual hypersensitivity to ionizing radiation, which has recently come to light. Some patients have extreme hypersensitivity that can lead to “radiological burns” following a simple X-ray. There is in these patients, even at low doses, a cellular radiosensitivity which could concern approximately 5 to 10% of the population. It is easy to imagine the danger posed by scanners for this type of population or the systematic use of mammography for breast cancer screening. Tests for highlighting individual hyperradiosensitivity should see the light of day…in a few years.

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In the meantime, the only possible precautionary measures are to discuss with your doctor when ordering a medical X-ray or CT scan, to ensure that there are no other types of tests available that avoid to take doses of radioactivity. And to keep a notebook of “doses received” following examinations or treatments to keep in mind an idea of ​​the doses received each year.

Some significant figures relating to exposure to radioactivity (source IRSN)

X-ray image: 0.004 mSV

A chest X-ray: 0.02mSV

A return Paris-New York flight: 0.06 mSv

A mammogram: 0.1mSV

Annual permissible dose limit received by the population from exposure of artificial origin, excluding medical: 1mSv

Average annual dose of exposure to ionizing radiation of natural origin: 2.4 mSv

Average dose for an abdominopelvic scan: 10 mSV

Limit of permissible doses received by workers exposed as a result of their professional activity: 20 mSv

Lowest dose known to trigger cancer: 100mSv

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