A recent unique workplace injury case has drawn attention. After a Korean Air flight attendant died of stomach cancer, the Korean authorities recognized this incident as a case of occupational injury due to cosmic radiation for the first time.
The Korean Workers’ Compensation and Welfare Service revealed that the flight attendant flew an average of 1,022 hours per year from 1995 to 2021. This incident has sparked public concern about radiation exposure during air travel.
So, what is cosmic radiation? Does cosmic radiation affect the human body? A Science and Technology Daily reporter interviewed relevant experts on this topic.
Radiation Exposure During Flights is Within Safe Limits
When radiation is mentioned, many people react with fear. In fact, radiation is a general concept that includes various types and is ubiquitous.
Professor Liu Libo from the School of Public Health at Jilin University explained that the radiation that may impact human health is mainly ionizing radiation, which includes radiation from medical equipment like CT scanners and X-ray machines. The radiation received by people on airplanes also falls under ionizing radiation.
Bian Yueyue, a senior engineer at the China Geological Museum, noted that ionizing radiation can be divided into artificial radiation and natural radiation, with the latter also known as background radiation. Artificial radiation mainly comes from human applications of nuclear technology, such as radiation from CT scanners.
Background radiation is naturally occurring and comes mainly from cosmic rays and radioactive nuclides in the Earth’s crust. This type of radiation has existed for much longer than humans have.
Aviation radiation is produced when cosmic rays penetrate the Earth’s atmosphere. These cosmic rays usually have extremely high energy and travel through space at nearly the speed of light. The equatorial region receives the least cosmic radiation, while the polar regions receive the most.
Due to the Earth’s magnetic field and atmosphere, the majority of cosmic rays are largely dissipated by the time they reach the ground, posing minimal impact on humans. However, the higher the altitude, the more cosmic radiation people are exposed to. Studies show that for every 2,000-meter increase in flight altitude, the dose of cosmic radiation exposure doubles.
The unit for measuring radiation dose is usually millisievert (mSv). Bian Yueyue explained that for people living at low altitudes, radioactive nuclides in the Earth’s crust are the primary source of background radiation, found in soil, rocks, and oceans. The average background radiation in China is about 3.1 mSv.
When an airplane flies at an altitude of 10,000 meters, the radiation dose from cosmic rays is approximately 0.006 mSv per hour. For instance, on a flight from Beijing to Shanghai, with about 2 hours of flight time, passengers are exposed to a radiation dose of only about 0.012 mSv, which is well within the safe range.
No Need for Extra Radiation Protection in Daily Life
The National Nuclear Safety Administration, following recommendations from the International Commission on Radiological Protection, has established the “Basic Standards for Ionizing Radiation Protection and Radiation Source Safety” (hereinafter referred to as the “Standards”).
The “Standards” mainly focus on ionizing radiation protection in the field of nuclear science and technology and are primarily applicable to workers exposed to ionizing radiation in their jobs. For these workers, the “Standards” stipulate that their average effective radiation dose over five consecutive years should not exceed 20 mSv per year, and no single year’s dose should exceed 50 mSv.
The “Standards” do not specify the annual safe radiation dose for the general public. For specific groups of people who might be near ionizing radiation facilities, the “Standards” state in an appendix that their annual average dose should not exceed 1 mSv. In special cases, if the five-year average annual dose does not exceed 1 mSv, a single year’s dose can be increased to 5 mSv.
However, it is essential to clarify that the dose limits provided in the “Standards” exclude unavoidable background radiation. Moreover, the doses specified are for the effective management of nuclear technology applications and practices, not to determine whether humans are harmed.
For example, a single X-ray examination exposes people to about 0.2 mSv of radiation, while a CT scan can expose them to 2 to 10 mSv of radiation. Although these figures exceed the 1 mSv limit in the “Standards,” it does not mean the body will necessarily be affected.
Furthermore, voluntary acceptance of medical radiation is not within the scope of the “Standards.” It is generally believed that health risks significantly increase only when the annual radiation dose exceeds 100 mSv.
Liu Libo stated that in daily life, unless there are special circumstances, additional radiation protection is not needed. If medical radiation is required, it is essential to strictly follow medical advice and undergo the necessary examinations according to the prescribed frequency.
