AW: [ RadSafe ] In-flight radiation benefit

[Rainer.Facius at dlr.de]

Thanit:

I want to add to the short answers you obtained by now.

The radiation doses which flight crew at commercial flight altitudes (up to FL 400) accrue average around 3 mSv per year which is well below the limit of 20 mSv per year which terrestrial radiation workers are allowed to receive in Europe and according to ICRP. 

The above world wide mean value of 3 mSv per year averages over geomagnetic latitudes, flight altitudes and solar activity cycle. So far, measured exposures typically range from 1 mSv per year for crew serving mainly equatorial routes to at most 6 mSv for crew flying chiefly intercontinental routes near the poles. As a function of the geomagnetic latitude, the dose rates for any given flight level saturate at latitudes above about 60 degrees. So flying polar routes is normally not too different from flying long distance North Atlantic routes. All this pertains to the regular exposure to the normal source of galactic cosmic rays (GCR) or rather their fragments remaining after their passage through the about 200 g per cm^2 air which they have to traverse before reaching you at FL 400.

Regarding the irregular irradiation from occasional energetic solar particle events (SPE), their impact on your radiation exposure is entirely restricted to geomagnetic latitudes above 50 degrees. There, the vast majority of these SPEs add to your radiation doses hardly more than an hour or so added flight time would do. Actually, following the more intense SPEs, the regular GCR dose rate is often substantially reduced for several weeks by the so called Forbush decrease, so that the net effect of many SPEs could in reality be a reduction of your annual exposure. Very rarely, i.e. about once a decade, the exposure from very large SPEs matches the normal GCR dose which you receive during a flight London-Seattle. Even more rarely, i.e., about twice a century you might expect to receive from a single SPE a dose which approaches the limit set for pregnant women, i.e., 1 mSv.  Of course the uncertainties of these frequencies are quite large, given the small numbers of observations which they are based on, but that is what we know. 

The above exposures pertain to duty times of typically less than 1000 block hours a year. With your companies goal of 1500 block hours per year (hopefully paid properly) you might expect to accrue about 9 mSv per year. That compares to exposures which people receive when living in areas of high natural background radiation, such as in Cornwall, Massif Central (France), Kerala (India), Yangjiang (China) or Spas like Ramsar (Iran) and Bad Gastein (Austria), the latter two featuring actually significantly larger dose rates. Yet nowhere has an increased rate of cancer incidence/mortality been observed in these populations. Quite the contrary, a slightly negative - though statistically insignificant - trend of cancer mortality with increasing dose is often observed. This agrees with the - again statistically insignificant - negative trend observed in the so far largest epidemiological study of cockpit crew.

I hope that helps.

Regards, Rainer Facius

Dr. Rainer Facius
German Aerospace Center
Institute of Aerospace Medicine
Linder Hoehe
51147 Koeln
GERMANY
Voice: +49 2203 601 3147 or 3150
FAX:   +49 2203 61970

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag von howard long
Gesendet: Mittwoch, 3. August 2005 19:18
An: Fly High; radsafe at radlab.nl
Betreff: [ RadSafe ] In-flight radiation benefit 

Thanit,
BENEFIT of up to 10 rad/year (rem, cSv,- all the same), about 100 x usual background, 10  CT scans, and much more than you get at 35,000 feet for 1500 hours (unless sun spot storm) - can be found in thousands of references.
 
For example,
" Is Chronic Radiation an Effective Prophylaxis Against Cancer?" Chen, Luan et al, can be found at www.AAPSonline.org under Departments, Journal of American Physicians and Surgeons, Spring 2004 pp 6-10. 
 
10,000 persons exposed to av 40 cSv (rad) over 10 years (from Co60 in re-bar of apartments) had less than one-tenth the expected cancer and fetal deformities expected!    

Howard Long MD MPH

Fly High <fly5515 at yahoo.com> wrote:
Dear all doctors,
 
I have read your dicussions about in-flight radiation.  I'm a pilot who trying to find the effect of cosmic radiation to us.  Frankly I'm not quite understanding your discussions, there are many terms that not familiar to me.  I'm very confused cause I think that in-flight radiation considered to be harmful.  Any of you can kindly explain to me the real effects of radiation to our health?  Is it really benefit or harmful?  What is the criteria we should considers?
 
The background reason why I search for the radiation effects, is that our company try to push us to fly more.  While the major airlines reduce flying time for their employee, ours try to increase.  With the new route fly pass near polar and ultra-long flying time (16-18 hours per flight), the company can't find enough pilots to fly all the routes.  So the management has asked our authority to increase the allowable fiscal year flying time up to 1400-1500 hours.
I'm not sure about the intensity of radiation near polar but suspect to be strong also the exposeure times is long too.
 
Could any of you kindly explain in simple language to me?  Thanks for your attention and sorry to waste your precious time.
 
Sincerely,
Thanit Vittayaprechakul

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