To fly or not to fly? Ionizing radiation in aircraft | Business

The radiation in the plane is tens of times higher than on the ground

in 1912 Victor Franz Hess, an Austrian-American physicist and winner of the Nobel Prize in Physics, while flying in a hot air balloon, invented a Geiger-Muller counter to measure how the intensity of natural, ionizing radiation coming from the depths of the Earth decreases as it goes up.

Understand instantly

• As flights intensified, interest in cosmic radiation grew, as the question of whether it posed a danger to those traveling by air became more frequent.
• When flying an airplane at an altitude of 9-12 kilometers, the radiation experienced by the passenger and crew member ranges from a few to several tens of microsieverts, that is, tens or even hundreds of times more than on the surface of the earth.
• Airline crew members spend significantly more time on an airplane in flight than frequent flyers, so their radiation safety is given more attention.
• The Radiation Protection Center (RSC) annually collects and analyzes aircrew exposure data.
• Although passengers flying in aircraft are exposed to cosmic radiation, this exposure is so low that there is no reason to worry about health effects.

To his surprise, he found that the higher the balloon rose, the stronger the ionizing radiation was. Thus, another type of radiation was discovered, which was later named cosmic radiation.

Cosmic rays reach the Earth’s atmosphere from all over space.

It has been established that cosmic rays reach the Earth’s atmosphere from all over space. By the way, the term “cosmic rays” is a bit misleading, since cosmic rays are streams of particles, not a beam as we understand it when talking about light.

Earth is protected from cosmic radiation by its magnetic field and atmosphere. Therefore, when we walk at sea level, cosmic radiation is negligible from a radiation protection point of view.

The intensity of cosmic radiation is not constant, it changes. The changes are driven by three main factors:

• height above the Earth’s surface (sea level);
• geomagnetic latitude (flight route);
• Solar activity (flight date).

The table below shows data from the study “Radiation dose to the global flying population” conducted by the Massachusetts Institute of Technology, showing the exposure experienced by passengers and crew members when flying on certain long-haul routes.

RSC archive photo. / Infographic

According to the Radiation Protection Center (RSC), the dose that a person receives when flying from Vilnius to London is 3.8 µSv – as you can see, it is ten times lower than when flying on long routes.

For comparison: the ambient radiation background in Lithuania is 0.05-0.15 µSv/h, so it is easy to calculate that if you are not in an airplane but on the ground for three hours, you will be exposed to 0.15-0.45 µSv.

The dose received by a patient during a chest radiograph is 20 µSv, the dose received by a patient during an abdominal computed tomography procedure is 10,000 µSv, and the permissible dose for a worker working with sources of ionizing radiation is 20,000 µSv (20 mSv) per year.

As altitude increases, atmospheric air density decreases, so the higher we are above the Earth’s surface, the smaller the air mass above our heads. Therefore, when flying an airplane at an altitude of 9-12 kilometers, the radiation experienced by the passenger and the crew member is from several to several tens of microsieverts, that is, tens or even hundreds of times more than on the surface of the earth.

The higher we are above the Earth’s surface, the smaller the air mass above our heads.

Taking this into account, aircraft crews (especially long-haul flights) are classified as occupational groups exposed to ionizing radiation. This is because workers working with ionizing radiation sources in industry, science, or medicine are typically exposed to no more than a few millisieverts (0.5-2 mSv) per year, and cases where higher doses are recorded are more likely to be associated with certain specialties , which are characterized by exceptional working conditions.

Meanwhile, an annual dose exceeding 1 mSv is almost inevitable for aircrew members regularly flying at 10 km altitude on long-haul flights, and in special cases it may exceed 6 mSv.

Nevertheless, for a long time there was no legislation regulating the exposure of aircrews, and no protection for pilots and flight attendants. Such an approach was based on the fact that cosmic radiation is of natural origin and therefore not a product of human activity that should be regulated in any way. However, over time, attitudes toward cosmic radiation have changed.

Shutterstock photo/Ryanair plane

Passengers flying occasional aircraft are exposed to less than the permissible limit for the population of 1 mSv (1,000 microsieverts (µSv)) per year because they spend far fewer hours in the aircraft than flight crew members. Of course, there is no such thing as harmless ionizing radiation, but such exposure to cosmic radiation is considered to have no health effects.

Radiation protection measures are applied in civil aviation

Airline crew members spend significantly more time on an airplane in flight than frequent flyers, so their radiation safety is given more attention.

Radiation protection measures for airlines whose aircraft fly above 8,000 m are determined by the legislation of the European Union and the International Atomic Energy Agency (IAEA). recommendations and the Lithuanian hygiene norm HN 73:2018 “Main radiation safety norms” prepared on their basis and the description of the procedure for the application of radiation protection measures in civil aviation and the exposure assessment of aircraft crew members.

Legislation states that airlines must:

• to prepare a radiation protection program for aircraft crew members and to carry it out;
• assess the exposure of aircrew members;
• to draw up the work schedules of the flight crew members in such a way that the additional annual effective doses of the flight crew members do not exceed 6 mSv;
• to register, store and provide the Radiation Protection Center with exposure data of aircraft crew members;
• pregnant crew members must inform the employer about the pregnancy, and the latter must take measures so that the radiation safety of the embryo or fetus meets the requirements for the radiation safety of the population, and the effective dose of the embryo or fetus during the remaining period of pregnancy does not exceed 1 mSv;
• when the annual effective dose of aircraft crew members exceeds 1 mSv, the employer must inform them about the additional exposure experienced and the possible consequences of the additional exposure to their health;
• when the annual effective dose of aircraft crew members exceeds 6 mSv, the activity must be registered in accordance with the procedure established by the Law on Radiation Protection and the radiation protection requirements set out in Chapter V of the Hygiene Norm HN 73:2018 must be applied to aircraft crew members.

The flight time of aircrews is controlled by the International Air Transport Association (IATA), which limits the exposure doses received by aircrews.

The Radiation Protection Center assesses the exposure of aircrew members

The Radiation Protection Center (RSC) annually collects and analyzes aircrew exposure data. After analyzing data provided by six aircraft companies on 3,553 flight crew members in 2023. exposure, it was determined that 41 percent cases the annual exposure exceeded 1 mSv, in all other cases the exposure did not reach 1 mSv. The largest in 2023 the annual radiation dose was 2.71 mSv, the average – 0.86 mSv.

After evaluating the 2018-2023 data on the exposure of aircraft crew members, it can be seen that the exposure of Lithuanian civil aviation air carrier crew members, in 2020-2022 was significantly lower than in previous years, in 2023 returns to the previous level more and more quickly with the entry into force of flight restrictions during the COVID-19 pandemic. When assessing the exposure of aircraft crew members, it should be mentioned that only short and medium-distance routes are flown from Lithuanian airports.

RSC archive photo. / 2018-2023 variation in exposure of aircrew members (RSC data)

According to the IAEA, the average annual exposure of aircrew members is less than 1 mSv if all routes flown are below the 9,000 m altitude limit. Crews flying on long-distance routes, whose routes pass near the Earth’s poles, receive a higher radiation dose of up to 6 mSv per year.

Aircrews flying on other long-haul routes receive 2-3 times lower doses per year (this shows the dependence of exposure on geomagnetic latitude).

So, is it safe to fly? Fly without fear, because although passengers flying in aircraft are exposed to cosmic radiation, this exposure is so low that there is no reason to worry about health effects.

For more information on radiation safety, see – Radiation safety of Lithuanian people.