Radiation

RADIATION

What and where is radiation, what are the effects of radiation on the human body, how much radiation are we exposed to and what can we do to minimise our exposure? An attempt will be made to answer these questions below.

What and where is radiation?

Cosmic rays hitting Earth. Credit: NSF/J. Yang

Credit: NSF/J. Yang

Radiation can be described as energy, and its unit of measurement is the “Sivert”, usually written as mSv (milli-Sivert= 0.001 Sivert). There are many sources of radiation during flights, such as from flight instruments, radioactive cargo and cosmic radiation. The last-mentioned one will be examined here.

Earth is continuously being bombarded with cosmic radiation, both from outer space and from the sun.

Radiation from outer space consists of charged particles, mainly protons and alpha particles as well as electrons and gamma rays. Collisions between protons and nitrogen and oxygen particles in the atmosphere form other charged particles such as neutrons, protons, etc.

Solar radiation consists first and foremost of protons and other charged particles as well as gamma rays. The emission levels of these particles from the sun varies in direct correlation with the sun’s level of activity.

The amount of cosmic radiation is, for the most part, dependent on three factors:

  1. Solar flares. Solar flares occur at regular intervals. These are dependent on the sun’s level of activity, which follows an 11-year cycle. The greatest radiation is at the magnetic poles, which cause the radioactive particles from outer space to turn or form spirals towards them.
  2. Flight altitude. Radiation increases with increased flight altitude because the atmosphere that protects us from radiation thins with increased altitude. On average, radiation doubles at each 6,500-foot increase in flight altitude.
  3. Distance from the magnetic poles. At 70°N, there is approximately four times more radiation at all altitudes than at 25°N.

 

What are the effects of radiation on the human body?

Several studies have been performed on pilots to investigate whether radiation can cause harm. What are the main risks?

  1. Risk of birth defects for expectant parents prior to conception. There is little risk associated with radiation on eggs or sperm for parents before conception. The likelihood of this is considered very low, or 1.5 in a million for each 1 mSv of radiation.
  2. Risk of foetal damage due to radiation during pregnancy. It is difficult to assess the risk posed to a foetus because it depends on the foetus’ stage of development. The maximum radiation limit for pregnant women is considerably lower than the allowable radiation for flight crews, see information below.
  3. Risk of increased frequency of life-threatening cancer. Many studies have shown that there is an increase in the frequency of cancer as a result of increased radiation. It is believed that radiation amounting to 5 mSv increases the risk of cancer by 0.02%. As a result, if a person receives 5 mSv radiation annually for 40 years, the risk will be 40 times greater, or 0.8% higher.
  4. The risk of increased frequency of cataracts. An Icelandic study has shown that pilots are three times more likely to develop cataracts than the general population.

How much radiation are flight crews exposed to?

The maximum radiation exposure of flight crews is 6 mSv per year*. The maximum radiation exposure of the general populace, however, is only 1 mSv per year, and as a result, the maximum radiation for pregnant women is only 1 mSv, based on the unborn infant.

The Icelandic Radiation Safety Authority annually issues a report on the radiation exposure of workers that work with ionising radiation, which includes flight crews (Icelandair). No direct measurements of individuals are carried out; instead, account is taken of a mathematical model and software that estimates the radiation exposure based on flight routes, flight altitude, flying hours and other factors. Flight crews are the most populous profession in Iceland exposed to radiation in their work, and their average radiation exposure is usually just more than 2 mSv.

Flight crews are the professions in Iceland that have the highest average radiation exposure compared with other professions. Other professions that work with ionising radiation are exposed to considerably less radiation. Further information on this report may be found on the website of the Icelandic Radiation Safety Authority, www.gr.is.

The flight crews of Icelandair can personally monitor radiation levels through:

My Work / Mínar síður, which contains links at the bottom to Flugfélags-websites and Globalog. Note that there are 1,000 microSv in 1 mSv.

Other flight operators probably provide the same information.

What can we do to minimise our exposure?

The main thing we can do is fly at lower altitudes in areas where the radiation is highest, such as at the magnetic poles and when there are solar flares. Radiation forecasts are issued by several entities that use information from satellites and/or information from stations on the ground. These radiation forecasts are issued daily, but few flight operators have taken advantage of this information and passed it on to pilots, who could use the information to reduce radiation exposure during flights.

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