Are X-rays dangerous to humans?
Exposure to radiation may scare some people. However, there are some points to remember when talking about harmful effects of radiation.
First of all, we are constantly exposed to radiation of various origins. This includes ionizing rays’ such as those used in radiology and nuclear medicine. Other types of radiation include infrared (heat). Ultraviolet (from which we tan and which ages the skin) and even visible light.
The ionizing radiation we are exposed to comes from the sun, natural elements in our environment, materials used in building the houses and even from natural radioactive elements in our bodies.
Depending on where we live, we are exposed to environmental radiation to a greater or lesser degree.
Cosmic rays reach us through the universe. Our atmosphere acts as a shield and drastically reduces the amount of rays reaching the surface. Therefore, the amount of radiation at high altitude is higher than at sea level: at sea level at the level of the equator, the dose of cosmic rays is 0.2 m5v (millisievert) per year while at 3,000 meters altitude 1 mSv per year can still be noted (so even during airplane travel, the dose is quite high 0. 1 7 mSv during a 6-hour flight).
Rock and soil also contain small amounts of radioactive material such as uranium, thorium,… . The concentration of these different elements varies greatly from place to place. In sandstone and shale, for example, the concentration is much lower than in granite. For Belgium, the annual dose of earth radiation varies from 0.45 mSv to 1. 1 0 MSv per year the separation follows more or less -the language border. Flanders has the lowest values and the province of Limburg has the highest average dose (0.90.7- 1.1 0 mSv/year).
Ingestion and inhalation of naturally occurring sources will subject our subjects to a radiation dose that is highly dependent on where we are or live and on our diet and other habits. Most of this dose is composed of Kallum40 and nuclides from the uranium and thorium series. KaliuM40 is naturally occurring and contributes to a dose of 0.2 mSv per year. Through the diet we reach 0. 1 7 mSv/year.
A major component of bodily radioactivity comes from gaseous elements such as Radon and Thoron. These are present in readily measurable concentrations In our atmosphere. They are inhaled by humans and enter our, food chain through plants and animals. Cereals have the highest concentration while milk, fruits and vegetables show lower concentrations.
The modern trend to, better insulate homes out of energy conservation has sharply increased the indoor problem of Radon and the like.
Curiously, the places with the highest radiation dose also have the lowest number, of cancer cases. This would mean that the risk of cancer is not demonstrably higher when exposed to low-dose radiation and that the cause of cancer spread must be sought in other environmental elements, such as smoking, traffic, chemicals, …
A second point to consider when estimating the risk of, a medical imaging examination is the fact that some examinations do not use radiation. By this we mean, for example, magnetic resonance and ultrasound. Both techniques have so far not provoked any negative impact at the doses used on medical imaging.
The examinations that do use ionizing radiation have a very low dose, similar to what we would pick up during an ordinary day. A typical dose for a standard radiology examination is between 0.1 5 mSv and 6.20 mSv. Some examinations give a higher dose up to 16.7mSv. With the evolution of the techniques used, the doses will become smaller and smaller with time. Despite many studies, there is still no evidence that radiology research with these doses is harmful to humans. Some experts believe that such doses are absolutely risk-free.
An idea of the radiation we are exposed to and its values can be found in the following chart.
The estimated dose for the average Belgian is 4.3 mSv/year, of which:
0.78mSv/year due to medical applications
2. 0.77mSv/year due to natural external exposure (e.g. cosmic rays, earth radiation,…)
3. 2.7 mSv/year due to natural internal exposure (e.g. inhalation of radon gas,…)
4. 0.05 mSv/year due to occupation, television….
The risks of radiation must always be weighed against its usefulness. A mammogram, for example, can detect breast cancer even before the lesion is physically palpable, thus saving lives. Therefore, the risk is far less than the benefit.
You may wonder why radiology technicians put themselves behind a screen during an examination, given the small risks. However, the answer is quite simple: the radiation dose during an examination is relatively small, but all examinations throughout the day give a cumulative high dose. There are numerous legal standards about the dose that radiology staff and even patients are allowed to receive. To meet those standards, medical imaging staff must follow a number of rules to keep the cumulative dose at a minimum.
Although the negative impact of low doses of ionizing radiation has yet to be truly proven, the medical community maintains strict standards for safety.
The IRCP (International Council on Radiation Protection and Measurements) formulates recommendations on limits for exposure to ionizing radiation. It is up to national governments to make these recommendations legally binding.
There are three categories of radiation protection among the population:
Occupationally exposed persons; The general population; Persons exposed to radiation for medical, therapeutic or diagnostic purposes.
For the latter group, there are no limits in terms of dose, as long as there is a reasonable relationship between the dose and its usefulness. We refer to this as the ALARA (As Low As Reasonable Achievable) principle, keeping radiation doses as low as possible while still achieving the best possible result.
For occupationally exposed persons, the limit is set at 20 mSv per year averaged over 5 years. I.e., the maximum dose is 1 00 mSv with a maximum of 50 mSv per year.
For the population, the dose is set at 1 mSv per year averaged over 5 years. I.e., the maximum dose is 5 mSv with a maximum of 2.5 mSv per year.
For pregnant women, the IRCP recommends an effective abdominal dose of no more than 2m5v from the time pregnancy is established; the European guideline value is 1 mSv.
For the sake of completeness, the so-called theory of the hormesis effect should also be mentioned here. It states that low doses of ionizing radiation increase the efficiency of repair mechanisms at the chromosomal level. Furthermore, low doses of ionizing radiation stimulate the immune system. This would mean increased resistance to certain tumors.
However, this theory is not yet widely accepted and is still the subject of scientific research.