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What is 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 RadiationCosmic 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 out 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.

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:
  1. 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
  2. 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.
  3. 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: 
  1. CPH-LAX 14. juli 2000 DEP 0700 ARR 1800 Duration 11 hours Radiation Dose: 80 μSv 
  2. 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.

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