The origin of cosmic radiation
Cosmic radiation originates from “The Big Bang”. Cosmic radiation consists of particles like protons, neutrons, electrons, myons as well as atoms. The particles were thrown out in all directions at a velocity close to that of light (300,000 kilometers per second). The result is that Earth – like all other celestial bodies in the universe – is bombarded from all directions with a stream of these particles, a phenomenon called galactic radiation.
Only a small number of these particles make it to the surface of Earth. Both the magnetic field and the atmosphere provide good protection from cosmic radiation. But at altitudes of 30,000 feet or more, people are much less protected and much more at risk from overexposure.
Cosmic radiation originates from back to the “Big Bang” – the creation of the Universe – about 13.7 billion years ago, when particles like protons, neutrons, electrons, myons as well as atoms were thrown ou
t in all directions at a velocity close to that of light (300,000 kilometers per second). On their way through space the particles at some occasions gathered into pulsating stars, which once again exploded where after the particles continued their travel through space. The result is that the Earth – like all other celestial bodies in the universe – is bombarded from all directions with a stream of these particles, a phenomena called galactic radiation.
Some of the particles are electrically loaded. This is true for the protons which carry a positive electrical load, and for the electrons which carry a negative electrical load, while the neutrons are neutral.
At the surface of the Earth we are well protected by the atmosphere the weight of which is – as we all know – 29.92 inches of mercury. The very small part of radiation coming through this protection corresponds to approximately 0.27 mSv annually (mSv = milliSievert = 1 thousandth Sievert, the unit used to describe the damage of biological cells). In comparison to this, the weight of the atmosphere at an altitude of 42,000 feet is 5 inches of mercury, i.e. a difference of 25 inches of mercury equivalent to 70 cm of lead – the lacking protection when flying at 42,000 feet.
Another important protection against the stream of particles from space is the so-called solar wind – a stream of particles ejected from the Sun, where nuclear processes of incredible force are continuously taking place. Debris from these processes practically sweeps away from Earth part of the galactic radiation.
As the solar processes are not constant, but – like the flames in a camp fire – flicker, the solar wind and consequently the Sun’s protection is continuously varying. In addition to this is the fact that the distance of the Earth and its relative velocity in relation to the Sun varies over a period of 11 years, and consequently also the protective effect of the Sun.
The third variable factor is the magnetic field of the Earth. As mentioned above some of the particles are electrically loaded. These loaded particles will follow the magnetic field which ends in the magnetic poles while the neutral particles are less affected. This means that the radiation over the poles is more concentrated than it is over the Equator.
From the above it is obvious that radiation is dependent of the altitude, of time in relation to the solar year, and of the position in relation the grid made up by latitude and longitude. During their long travel the velocity of the particles is reduced considerably so that they hit the atmosphere of the Earth with a velocity of “only” 800 – 1200 km/sec. However, this velocity is sufficient to cause ionization when these particles hit the air molecules of the atmosphere meaning – roughly – that they use part of their energy to smash the air molecules into similar small parts: atoms, new protons, and new neutrons.
All still containing sufficient energy to cause new ionizations (like a billiard ball shut into the pool). – Each particle – in spite of an increased number of hits – keeps sufficient energy to influence the biological cell. As energy – as generally known – is the product of mass and velocity, electrons and myons will contain so small amounts of energy that the impact with the biological cell will pass unnoticed. Quite a different with neutrons and protons which each have a mass equal to 2000 electrons. This energy filled particles can in unfortunate cases damage the long DNA molecules and cause a mutation. Such a mutation – a change in the genetic property of the cell – could be the ability to divide, and divide, and divide. Such an uncontrolled cell division is what we usually call cancer.
If the damaged cell happens to be an egg cell or a sperm cell the change of the properties will be transferred to the offspring, which most often will result in the death of the fetus, but in few cases may cause the child to be born with certain defects. Where the exposed cell belongs to a fetus that has already started its development the rapid cell multiplication may transfer the DNA damage to the organ under development at the time of the exposure.
There are five different types of cancer suspected to be related to radioactive exposure:
- Malignant Melanoma (skin cancer) A six times the normal occurrence of this type of cancer among 2,740 Air Canada pilots is, however, rejected by some epidemiologists as caused by radiation. The reason for this rejection is that “pilots more than other people have the opportunity to travel to warmer climates and expose themselves to the rays of the sun”.
- Astrocytoma (brain tumor) Twice the normal rate.
- Leukemia Four times the normal rate. – From the experience in Hiroshima and Nakasaki it has been proved that this type of cancer is related to radioactive radiation.
- Prostate cancer: There are speculations of whether this type of cancer may be caused by electromagnetic radiation from cockpit instruments and weather radar.
- Breast cancer An Icelandic study from 2003 states that the breast cancer rate for female cabin attendants having had flying duties more than five years was five times higher compared to the rate for female cabin attendants having flown for less than five years. – It must be added, however, that it is almost certain that this is not only due to cosmic radiation, as also inconvenient working times, stress, jet lag, late child birth, late breast feeding may be related to breast cancer.
The above statistics are all based upon INCIDENT STUDIES. However, there are also statistics based on MORTALITY STUDIES. And here it is interesting to note that pilots die less often from cancer than normal. Why? There are probably several reasons to this:
- Pilots belong to a group of the population called “healthy workers” – from nature they simply have been given a health better than normal (- or they would not have qualified for the pilot job). This good health makes the body capable better to resist the disease and – perhaps especially – the treatment
- Because of their need for a good health to keep their job, pilots are often rather much aware of what they eat and what they do with their body.
- But most important of all: the frequent medical examinations (every 6 months) will reveal a cancer so early that chances of a successful treatment are considerably higher. – but it must not be forgotten that even a successful treatment is not free of charge: fear of death, the possibility of losing a part of the body, the possibility of losing the job are all factors to be taken serious. A mortality study should never be presented to flight crew members as a proof of cosmic radiation being without risk to their health.
Unfortunately it has not been possible to find any studies that correlate the actually obtained doses with the rate of cancer, probably because there are no such studies. – In the many studies there is sometimes a correlation to years in the job (as in the Icelandic study above). But a pilot who during a lifelong career has flown only propeller aircraft will have been exposed to only a split of what another pilot has been exposed to during only 10 years on intercontinental jet flights.
The reliability of such studies will increase considerably when GlobaLog has been in use during some years as it then will be possible to correlate cancer incidences directly with the obtained exposure doses (as it is the intention to make these data available to science – anonymized and under the strict observance of national and international legislation of privacy protection). – With GlobaLog keeping radiation data back to 1958 it will be possible to draw valuable conclusions about cancer and radiation in a very few years to the extent that pilots can be motivated to enter their flights from the start of their career. Conclusions that otherwise may not be available the next three decades.
With reference to the above mentioned studies – and many others – there was a solid basis of arguments for the EU when the Council passed a directive in 1996 to make it mandatory for the air operators to calculate and register their crew members’ exposure to cosmic radiation (actually, the legislation is valid also for other industries that employ frequent flyers who, because of their employment, obtain radiation doses comparable to those of flight crew members).
The legislation was implemented (or should have been implemented) in 2002. At this time, however, it was related with an unreasonable degree of administrative burdens to make the calculation with the accuracy indicated in the directive. So initially the authorities accepted – for the time being – that the airlines used a computer program made available by FAA (CARI-6). Using the previous year’s average for the radiation strength they calculated the radiation doses for a number of their routes, divided the sum of the exposures by the sum of the estimated flying time for each route, and came out with an exposure per flight hour, i.e. 3.4 micro Sievert. Only thing left was to multiply this figure with each crew member’s flight time for the year.
The CARI-6 program was intended to be used on a monthly basis, as it normally is based on the monthly average of radiation strength. The program was originally designed by FAA in cooperation with NASA based on measured values on a large number of flights during different circumstances.
Radiation changes from minute to minute, usually not so much, but sometimes by a factor of 100 – 200 times during a shorter period. Using the monthly average means that crew members flying during such an event will not be credited the real value of their exposure. This may be a problem, certainly when considering the accumulated exposure, but also because we do not know if such solar events have any significant effect. With GlobaLog® the radiation is calculated minute-by-minute, so that crew members flying during high radiation are credited correspondingly. So are those flying during low radiation.
To demonstrate this, here are two flights, same route, same altitude, same duration, but with a difference in departure time of 36 hours:
CPH-LAX 14. juli 2000 DEP 0700 ARR 1800 Duration 11 hours Radiation Dose: 80 μSv CPH-LAX 15. juli 2000 DEP 1900 ARR 0600+ Duration 11 hours Radiation Dose: 53 μSv (Using the monthly average would have credited both crews with 67 μSv) Using an average (3.4 μSv – see above) of several routes does not work either.
Here are two flights: different routes, all other circumstances the same:
CPH-LAX 14. juli 2000 DEP 0700 ARR 1800 Duration 11 hours Radiation Dose: 80 μSv CPH-JNB 14. juli 2000 DEP 0700 ARR 1800 Duration 11 hours Radiation Dose: 42 μSv while 11 hours ea. 3.4 μSv would have credited both crews with 37 μSv.
DESCRIPTION OF GlobaLog®
GlobaLog® calculates the cosmic radiation to crew members during their duty. The calculations are automatically entered in an electronic logbook, which for the pilots contain all information as required by European and American Authorities, while it for the cabin attendants contain only the information necessary to refer any radiation dose to a certain flight.
Calculation of Cosmic Radiation:
GlobaLog® uses three basic levels of accuracy dependent on which data the air operators are able to supply us with:
- Calculations based on GPS data (time, altitude and position). – These calculations can be considered 100% accurate based on the scientific knowledge of the time for the calculations
- Calculations based on information on altitude and position for each segment of the flight. – These calculations can be considered better than 98% accurate (often close to 100%) based on the scientific knowledge of the time for the calculations
- Calculations based on the great circle track between the departure airport and the destination airport at optimum cruising levels reached via the established step climb procedure. – These calculations can be considered better than 95% accurate (often better than 97%) based on the scientific knowledge of the time for the calculations
For all three accuracy levels the radiation is calculated minute-by-minute with the radiation strength measured in exactly this minute, with the reported/calculated position and altitude for the aircraft.
As published in the annual report from the Radiation Protection Institute, to which employers to radiation workers (including the airlines) report the annual doses of the employees, personnel working with radiating material or apparatus are exposed to 0.99 mSv per year (for the highest exposed group), while air crew members are exposed to an average of 3.03 mSv (measured by the above mentioned average methods), but can – without any further measures – be exposed to 6 mSv.
It ought to be mentioned that in accordance with the ICRP (International Commission on Radiological Protection) radiation workers can be exposed to up to 20 mSv per year. But if the dose exceeds 6 mSv certain precautions with regard to health should be taken, and the documentation should be filed for at least 30 years or until the person in question reaches or would have reached the age of 75 years (whatever is longer). – In some European countries the limit of 6 mSv is fixed and must not be exceeded. In at least one country the limit of six is only valid if it is measured with an accuracy corresponding to that of GlobaLog®, otherwise it is 4 mSv. In the USA the case is a little different.
The NCRP (National Council of Protection and Measurements) has a limit of 50 mSv per year with regard to occupational exposure. However, 20 mSv/year or 50 mSv/year – a flight crew member would never come close to either. Both the ICRP and the NCRP set the limit for the general public to 1 (one) mSv per year. So why are the limits set 20 – 50 times higher for radiation workers? The answer is that the NCRP, ICRP, and other regulatory agencies assume that occupationally exposed people have chosen to accept the risks of their radiation exposure in exchange for the benefits of employment.
The balance of risks and benefits is intended to be fair or even advantageous to the worker. But in order – for the workers themselves – to evaluate the benefits towards the risks, they must have been informed about the risks, and they must know their exposure. Otherwise a legal problem could arise between a worker hit by radiation related cancer and his employer. It is consequently one of the requirements in the EU Directive that the air carriers are “to inform the workers concerned of the health risks their work involves”.
This is a task that GlobaLog® with great success has performed for its customers at several occasions. It is also a task that has to be performed with great delicacy in order to provide the proper knowledge without frightening the employees.
Today most crew members have heard about cosmic radiation and the related health risks. And there is no doubt, that the health risks are not underestimated, when crew members meet and talk. This is another reason to provide proper information to the crew members. Not doing this may become expensive. In Europe several airlines that have not given proper information, experience pilots flying lower than optimal in order to avoid radiation. – And providing a radiation account where the radiation dose can be checked continuously after each flying day will promote the safe feeling of each individual crew member. For each dollar spent on GlobaLog® hundreds of dollars may be saved on fuel.
It will always be a question of how far an employer must go to fulfill his responsibility to protect his employees against occupational damages. One thing that without doubt must be fulfilled is the commitment to inform the employees about the risks of their job in order to let them make an informed decision about their continued employment in the job. Another important thing is that the employer does all in his power to minimize the risk. In this case what could be done better than adopting the strictest rules on Earth (the European) and managing these rules with the most accurate tool there is GlobaLog®.
The fact that GlobaLog® is priced reasonably and makes the whole process easy and independent of airline staff resources, only adds to the value of GlobaLog®. And being able to follow the accumulation day by day makes it very difficult for a crew member to blame the airline of not taking care, especially if the account is kept within the limits of the strict European rules.
The rare case of any crewmember exceeding 6 mSv (and the real limit in most of Europe and in the USA being 20 and 50 mSv, respectively) there may still be the possibility of letting them continue flying, especially if the crew members in question sign a statement saying that they have received the proper information about the health risks involved with their occupation and that … etc. – pending legal practice in the state in question.
Once implemented GlobaLog® runs fully automatically without interference from airline personnel. From the files of the flight operations department the necessary data are exported to GlobaLog as soon as the system “sees” an On-Block Time (i.e. a concluded flight). The radiation for the flight is calculated and is distributed to each of the crew members on the crew list for the flight (active crew members as well as passive crew members and “deadheads”). – Immediately after the individual crew member can access his/her logbook by employing his/her user name and password.
For each flight the logbook will contain information about:
The Radiation dose for this flight.
The accumulated radiation dose.
The accumulated radiation dose for the calendar year.
The accumulated radiation dose for the last 365 days.
The accumulated radiation dose since the crew member declared herself.
The pilots’ logbook contains the specification of flight time (as required by FAA, JAA, and other CAAs), including an accurate calculation of night flying time together with the above specified doses of radiation. For Cabin attendants and passengers (passive transfers and “deadheads”) GlobaLog has developed a simplified logbook with only the data necessary to relate a specific radiation dose to a specific flight.
In addition to the individual logbooks an administrator logbook is available. This logbook provides a summary for all crew members to the benefit for the airline administration. From this logbook the administration can enter any crew member logbook for the closer analysis of any value. In coordination with the airline (and the crew organizations) the administrator’s logbook may be made available to the Aviation and Radiation authorities of the country.
GlobaLog® has a useful cooperation with FAA’s CAMI (Civil Aerospace Medical Institute), to which we make available the monthly average data, which we – as indicated above – do not find very valuable. The reason that CAMI is interested in our data is due to the fact that – while they get their data from only one neutron monitor – we get our data from a total of five stations positioned at five different positions on the Earth. This enables us to verify our data against each other, and it provides us with a continuous and secure data flow. This accuracy and continuity is of the utmost importance for GlobaLog® as we operate with minute-by-minute radiation data for the purpose of crediting the crew members with the actual radiation doses during the hours and minutes they were flying.
The GlobaLog® formula was first approved by the Danish Space Research Institute. Now GlobaLog® has been approved in several European countries as “suitable computer program” for the calculation of cosmic radiation exposure to flight crews. At the moment GlobaLog is setting the standard in Europe and beyond. – Global Aviation Data A/S was funded among others by the Danish Ministry of Science, Technology, and Innovation. During the development of the concept, GlobaLog® was domiciled at the Danish National Laboratory in Risoe, where most of the radiation knowledge in Denmark is concentrated.