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total risk will thus rise from about 22% to about 22.2%. In other words: if one thousand airmen have a
normal flying career, the expectation is that two of them would eventually die of cancer as a result of
occupational exposure to radiation. Based on normal expectation for the adult population, about an
ICAO Preliminary Unedited Version — October 2008 II-1-14
additional 220 of the 1000 airmen would die of cancer from causes unrelated to occupational radiation
exposure. There is, of course, no way of telling whether a specific cancer is caused by background
radiation, occupational radiation or other factors.
A liveborn child conceived after radiation exposure of its parents is at risk of inheriting a genetic
defect that may lead to a serious health impairment. From each parent’s exposure, the risk coefficient is
1.5 in 1 000 000 per mSv. If a female crewmember works for ten years and thus is exposed to an
additional 28 mSv, the risk to the child as a result of work related exposure to radiation would be
approximately 28 x 1.5 = 42 in 1 000 000. In the general population about 6% (or 60 000 in 1 000 000) of
the children are born with anomalies that have serious health consequences. In other words: if 23 800
children were born after occupational radiation exposure of their mothers, one of them would have a
congenital genetic defect or eventually develop a genetic disease as a result of his mother’s occupational
exposure to radiation. Based on the normal expectation for newborn children, an additional 1428 children
of the 23 800 would have genetic defects from other causes.
Recommendations
In view of the fact that ionizing radiation is now assumed to play a role in mutagenic or carcinogenic
activity, any procedure involving radiation exposure is considered to entail some degree of risk. At the
same time, however, the radiation-induced risks associated with flying are very small in comparison with
other risks encountered in daily life. Nevertheless such risks are not necessarily acceptable if they can be
easily avoided.
Theoretically, the radiation exposure in air crew can be reduced by optimizing flight routes and crew
scheduling, and by installation of radiation warning devices5. Such devices are particularly effective in
detecting high momentary radiation during solar flares and can thus be used in determining a need for a
lower cruising level. Female crew members should be aware of the possible risk to the foetus and should
be scheduled in such a way as to minimize the exposure during pregnancy.
Much study has been directed to the potential hazards of cosmic radiation (CR) to flight crews and
passengers of supersonic transport (SST) aircraft. Measurements show that in the high latitudes above
50N the maximum total body dosage at 65 000 ft (~20 000 m) – an altitude approximating the cruise
altitude of SST aircraft - is about 0.013 mSv/hour. Because of the reduced journey time the dosage per
unit of distance traveled is about the same as in current subsonic jets where 0.005 mSv/hour is recorded
during flights at about 37 000 ft (11 000 m) and at latitudes around 45ΕN. CR is not therefore expected to
be significantly more hazardous to the flight crews and passengers of SST aircraft, as even if the mileage
flown by crews were to be doubled, the effects of CR would not be regarded as harmful. As previously
stated, Annex 6, Part I, (paragraphs 6.12 and 11.1.17) contains provisions concerning radiation
monitoring in aeroplanes operated above 49 000 ft (15 000 m).
5A radiation warning device (an in-flight radiation dosimeter) was used in the Anglo-French supersonic transport
(SST) aircraft Concorde. This device provided a continuous display of the radiation dose rate.
ICAO Preliminary Unedited Version — October 2008 II-1-15
OZONE
Ozone is triatomic oxygen, O3. Stratospheric ozone is formed by the action of ultraviolet light on oxygen
(3 O2 > 2 O3). It is found in varying quantities, the peak values being recorded at about 35 000 m
(115 000 ft) with negligible values at or below 12 200 m (40 000 ft) and much reduced levels above
42 700 m (140 000 ft). The cruise altitude of commercial SST aircraft in northern latitudes, about 18 450
m (60 000 ft), could produce levels of ozone of 2 000-4 000 μg/m3 (1-2 parts per million (ppm)). Ozone is
destroyed by heat, by the catalytic action of some materials including nickel and by organic compounds.
Total destruction occurs at 400°C (750°F). Air in the cabin pressurization system of one type of SST
(when SST public transport operations were undertaken) is heated to 600°C (1 120°F) and this heat is
utilized to destroy ozone. However, it has been reported that when engine power is reduced to initiate
　
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