By Exequiel Sanhueza *
Our sun, the Sol Invictus for the Romans or the Ra for the Egyptians, is a yellow dwarf star within the immense universe of stars and fortunately it still has enough capacity to give us warmth and life; the necessary and vital heat for our subsistence.
However, for commercial aviation that flies high-performance aircraft at high altitudes, for its passengers and for its crew, our Sun is a huge concern. This has led scientists to develop an area of meteorology called Space Weather, which aims to study, in real time, the behavior of the solar wind or the detachment of part of the solar corona and its impact on the magnetosphere, this essential part of the Earth’s atmosphere that protects us from solar radiation and cosmic rays from interstellar space.
The impact of the Sun on our magnetosphere usually generates geomagnetic storms that, at times, can cause damage to the terrestrial infrastructure, interference in the necessary and fundamental aeronautical communications, errors in global positioning systems (GPS), health problems to passengers and crews. When this occurs, polar and sub-polar flights must be diverted to lower latitudes, generating huge losses for air operators. To the above, we must add the South Atlantic Anomaly, a place where the intensity of solar radiation is higher than in other regions of the globe, due to the weakening of the magnetic field, in a vast region, ranging from South Africa to the north of Argentina and from there to the north.
As a corollary, it is these geomagnetic storms that generate the beautiful northern or southern auroras, so commonly admired by tourists, especially those from the northern hemisphere.
I have been stating, for a long time, a special concern about this issue that affects the health of passengers and crews, without ignoring the concern and study of some governmental aviation agencies, ICAO, NASA, some Associations of Pilots and Cabin Crew Members and from medical organizations that, for decades, have been writing about the illnesses of those exposed to permanent radiation.
The highest US aviation authority, the FAA, in its AC 120-42B, regulates polar and sub-polar operations. Such document, in one of its sections, states: “The certificate holder must provide a plan to mitigate the exposure of the crew, to the effects of the activity of solar flares, at the altitudes and latitudes expected in such operations.” Similarly, it is stated that: «For dispatch considerations and crew members during the solar flare activity, the certificate holder must know the content of AC 120-52, Exposure to radiation of the crew members of the certificate holder and provide training to crew members, as established in AC 120-61 ».
I remember that in 1986, a group of scientists from the Chilean Nuclear Energy Commission measured solar radiation on board Lan Chile airplanes, on routes such as to Punta Arenas, Easter Island and the South Pacific.
However, I must express my great dismay, seeing that no concrete actions have been taken on this delicate matter, especially since the crews have been and will continue to fly, routinely, at high altitudes on long flights, permanently exposed to high solar and cosmic radiation.
All this happens when the World Health Organization has pointed out that “the damage that radiation can cause to organs and tissues depends on the dose received, or the absorbed dose; it also depends on the type of radiation and the sensitivity of organs and tissues.” NASA has also pointed out that “cosmic radiation breaks DNA and produces free radicals, which can alter cellular functions.”
Solar activity has its maximums and minimums, every eleven years. This year we are in the presence of a solar cycle of maximum intensity. However, in periods of minimum intensity of solar radiation, which should favor us, high-energy cosmic rays from outer space and, in particular, from a very massive star called Cygnus OB2 are allowed into our terrestrial atmosphere. Cygnus OB2 is located 4,600 light years from Earth, according to a recent study by Michigan Technological University in the USA and the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow.
Spaceweather noted in January 2020 that “radiation appears to be increasing at almost all altitudes, even in the range of 25,000 feet to 40,000 feet, which is where commercial aircraft typically fly. Therefore, flight crews and passengers on polar flights are absorbing approximately 12% more cosmic radiation than a few years ago.
It is interesting to note that a new predictive model of aviation radiation called the E-RAD-Empirical RADiation has been developed. For this reason, radiation sensors are constantly being flown on airplanes over the United States and around the globe. So far, more than 22,000 GPS-tagged radiation measurements have been collected. As Spaceweather notes, “approximately 1,400 flights crossing the 10 busiest continental routes in the United States are monitored every day. Typically this includes more than 80,000 passengers per day and E-RAD calculates radiation exposure for each flight.
Similarly, it is interesting to note that the Superintendency of Labor Risks of Argentina published cosmic radiation in commercial aviation, including radiation received by passengers and crew, both on long and short flights. This entity also maintains that “there are various computer systems available on the market, capable of calculating the exposure doses for crew members. Some of them are EPCARD (Germany), PCAIRE (Canada), CARI (United States) and SIEVERT (France).”
Likewise, it is very interesting to highlight the work that is being done in Mexico where «in collaboration with the Aviators’ Union Association (ASPA), a study is being carried out to measure the doses of ionizing radiation received by the members of commercial aircraft crews, using thermo-luminescent dosimeters, as indicated in the XII National Congress on Solid State Dosimetry».
Similarly, from December 2018 to February 2019, Harvey Allen of the Network Startup Resource Center at the University of Oregon carried ground-to-air radiation sensors, including neutron bubble chambers, on board commercial flights from North America to Europe, Africa, South America and Asia, completing a total of 83 flight hours. The result was that they found deep space neutrons on every flight. It is further noted that ‘at least one study shows that the low radiation dose received over a long period of time may slightly increase the risk of leukemia, whereas pilots and cabin crew have been found to have a higher risk of cancer than the general population ‘. This confirms that the crews receive, during their work, doses of ionizing radiation higher than the limit recommended by the International Commission on Radiological Protection.
But then, what is the solution or solutions to this disturbing and worrying problem in the face of so much scientific evidence?
There may be several alternative solutions, however, I dare to point out some among many others. One of them could be to limit the monthly flight hours to those crew members who fly above 25,000 feet of altitude on long flights. Another would be to eliminate the passenger windows, which would also mean improving the aerodynamic performance of the aircraft and, consequently, contributing to the reduction of greenhouse gases. Another alternative solution would be for the aviation industry to accelerate the research and development of windshields for the flight deck and passenger windows, which prevent the entry of harmful radiation into the fuselage of the aircraft.
As long as there is no concrete solution to this problem, cosmic rays will continue to penetrate aircraft, dosing pilots, cabin crew and frequent travelers with potentially significant doses of ionizing radiation.
(*) Exequiel Sanhueza, is a retired Airline Pilot and currently works as Professor at the Aeronautical Training Institute (ICA), in Cordoba, Argentina.