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doubled by an increase in altitude from sea level to about 5000 feet and this doubling continues up to
about 70 000 feet). High altitude flight therefore increases the degree of exposure to cosmic radiation. The
polar regions have a greater radiation intensity than the equatorial regions, owing to flattening of the
atmosphere over the poles and the shape of the earth’s magnetic field.
Many studies have been conducted aboard airliners, mainly flying on North Atlantic routes, to
establish the amount of radiation to which the air crew are exposed. Based on these studies, it is possible
to calculate a radiation exposure of approximately 5 mSv per year for air crew flying 600 hours per year
north of N50 at altitudes above 39 000’, and approximately 3.3 mSv per year if the flight level is reduced
to altitudes around 33 000’. If the annual flying hours are calculated for cruising only (with deduction for
start, climb, descent, and landing) to 400 hours per year, the radiation exposure will be around 2 mSv.
Flying south of N50 will entail a further reduction in exposure.
31 Gy = 1 joule/kg = 100 rad (absorbed radiation).
41 Sv = 1 joule/kg = 100 rem
(dose equivalent = 1 Gy for β-radiation).
ICAO Preliminary Unedited Version — October 2008 II-1-13
In a recent study conducted by the national airline in a Contracting State, situated between N60 and
N70, the maximum radiation exposure in full-time air crew measured during ordinary scheduled flying
over one year was 2.8 mSv.
Maximum Exposure
The maximum radiation exposure, recommended by ICRP, for individual members of the public is 1 mSv
per year or, in particular cases, 5 mSv per 5 years. For workers exposed to radiation (and therefore under
special surveillance which may include annual health examinations) the recommended limit is 100 mSv
per five years or an average of 20 mSv per year with a maximum of 50 mSv in any one year. For pregnant
workers the recommended limit is 1 mSv per year or the same for the foetus as for any other individual
member of the general public.
Use of Computer Programmes to Estimate Dose
It is possible to estimate the radiation dose for a certain route by using a computer programme developed
for this purpose. The data to be input are the date and location of departure, the flight profile, detailing the
time in climb, cruise and descent, and the time and location of arrival.
One such programme, which is simple to use and has been validated, is produced by the Civil
Aeromedical Institute (CAMI) in the United States. CAMI was previously known as the Civil
Aeromedical Research Institute (CARI). The latest version of this computer programme is called CARI-6
(dated 7 July 2004). It can be down-loaded from CAMI’s website or accessed on-line at
http://jag.cami.jccbi.gov./cariprofile.asp. A similar European programme, EPCARD (European Program
Package for the Calculation of Aviation Route Doses), has been developed and is available on-line in
English and German at www.gsf.de/epcard2/index.phtml.
Risk Assessment
Ionization can cause chemical changes in living tissue and may thus affect the behaviour of living cells.
This can lead to cell death (as in acute radiation sickness) or to alteration of genetic material within the
cell (so-called mutation as seen in late sequels). The latter can induce cancer or lead to anatomical defects
in a foetus. These effects, however, are dose related: low doses of radiation carry a low risk, and the lower
the radiation dose is, the longer is the interval from exposure to development of disease, often many
years.
We have no exact knowledge about the risk of low dose radiation, but studies of the survivors from
the Hiroshima and Nagasaki atomic bombings in 1945 indicate that a radiation dose of 500 mSv leads to
development of cancer in about 1% of those exposed. Consequently, according to the theory of linearity, a
radiation dose of 1 mSv entails a cancer risk of 0.002% (1 mSv is about 1/3 of the natural background
radiation, vide supra). With few exceptions the incidence of cancer has not been increased detectably by
doses of less than 100 mSv.
It is generally estimated that 1.5% of all fatal cancers in the general population result from natural
background ionizing radiation. A man, living on Earth for 70 years, will receive a total dose of ionizing
radiation of about 210 mSv. His risk of developing a cancer due to radiation is about 0.42% or one in 238.
If he flies as an airline pilot for 40 years he may receive an additional dose of some 112 mSv which
entails an additional cancer risk of about 0.22%. The over-all risk of acquiring a fatal cancer disease (all
types, all causes) during a lifetime is about 22% (including 0.42% caused by radiation). The airman’s
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