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Radiation doses

Old 27th Jan 2011, 04:08
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Radiation doses

Mrs JO is in medical imaging and is told to brief patients: "This mammogram X-ray exposes you to no more radiation than a long haul flight".

She asks is this true? (obviously, in general terms only; and yes, the radiations are different in source and frequency but are both ionising)

And the question arises: "What is the current view on hazards of aggregate radiation exposure for long haul crews?" (or pax, for that matter)

(My perfunctory search did not bring much up but maybe wrong words used)
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Old 27th Jan 2011, 08:23
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Dr Michael Bagshaw, who had done some work on Concorde, states (full transcript of the symposium at http://www-hsd.worldbank.org/symposi...-bagshaw.htm):
"The Concorde flies up to 60,000 feet and gets a higher dose of radiation than a subsonic airplane. So for the last 25 years, we've been monitoring cosmic radiation exposure on the Concorde. We also monitor cosmic radiation exposure on our long-haul aircraft. The International Commission on Radiological Protection recommended dose limit for a worker, is 20 milliSieverts per annum?
If you take the radiological protection practice of taking three-tenths of the occupational exposure as being the limit for deciding whether a worker is a controlled worker or not, that works out at six milliSieverts per annum?.
Our work shows that the average Concorde flight crew are getting about four milliSieverts per year. Theoretically, they can go up to six, although we've got no crew members who do reach six. Long-haul crew flying 747s on very long range—over the Poles, over the Northern latitudes— get on average between four to five, with a maximum of five milliSieverts, and short-haul crew operating in Europe are getting about three milliSieverts per annum.
So what we're finding is that cosmic radiation exposure is well below the International Commission on Radiological Protection standard, and our epidemiological studies show that our long-haul crew on average live about five years longer than a matched population. And after the discussion this morning, I won't start talking about matched populations, but we've done intensive epidemiology, and we're part of the pan-European study which is looking at morbidity and mortality in crew.".

However with the full-body scanners coming is use in the US, there may be an increase in the radiation exposure (Increasing Safety or Risking Lives – Airport Body Scanners | Aviation Medicine :: Aerospace Medicine).
FYI, pl
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Old 27th Jan 2011, 18:15
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Medical radiation probably sparks off about 200 cancers a year in the UK.

If "background" radiation for Jo Average is 1 day, a Chest X-Ray is about 3 days.

Back X-Rays are about 5 months.

CT of the belly is about 4-5 years.

This is one of the reasons GP's don't rush to fill in the x-ray form, (not 'cos they don't love you or they're protecting a budget.)

Have a look at Making the Best Use of a Department of Clinical Radiology by The Royal College of Radiologists.
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Old 27th Jan 2011, 22:28
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Mrs JO is in medical imaging and is told to brief patients: "This mammogram X-ray exposes you to no more radiation than a long haul flight".

She asks is this true?
No, it does not appear to be true, at least based on figures I was able to dig up. A typical single long-haul airline flight results in an exposure of about 0.02-0.03 mSv, which is about twenty to forty times less than a typical mammogram at 0.7 mSv. So a single mammogram is probably roughly equivalent to about a year's worth of air travel for a frequent business traveler.
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Old 28th Jan 2011, 02:03
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Those figures look about right, I think the missing factor is that of 'effective dose', ie the whole-body dose associated with the same overall risk. When only a small part of the body is irradiated, such as the breast alone, a tissue weighting factor is applied to calculate the effective (whole body) dose with the same associated risk. Some organs and types of tissue are considered more sensitive to radiation and have higher tissue weighting factors than others. For breasts the factor is 0.05, which if multiplied by the 0.7 mSv mentioned above gives 0.035 mSv effective dose - not far off the figure for the long-haul flight, for which the whole body is exposed of course (tinfoil hat or no tinfoil hat....)

So in a way, she is probably correct as long as she has a whizz-bang newer digital mammography set to use rather than the old style which would I reckon give more than 0.7 mSv.
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Old 28th Jan 2011, 18:24
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Sorry mphysflier but it is rather more complicated than that. The ED is a simple summation of each tissue in the body. It takes no account of the relative absorbtion of certain tissues such as bone which is 9 times higher, nor does it correct for age related risk. We use the ED merely as a measure of total exposure when using continuous X ray screening.

Risk is somewthat different. It has been estimated that CT scanning in the US alone will cause 29,000 extra cancers per year of use. Whereas the risk to the individual is low and normally offset by benefit, the risk, for example of an abdominal CT is greater than the risk of detecting bowel cancer in an unsymptomatic person up to 40.

The suggestion that diagnostic radiology is no more dangerous then flying is I regret far from the truth, so I wouldnt give up the day job just yet.
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Old 30th Jan 2011, 08:40
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Thank you

Thank you for the contributions everyone. Appreciated.
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Old 9th Feb 2011, 22:16
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I'm a Capt for a Middle East airline on long-haul. We currently have no Radiation Monitoring for crews. I would be interested to know what monitoring is done by other airlines. Do you use Monitoring Cards for example which register the dosage of radiation on a continuous basis??
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Old 10th Feb 2011, 04:01
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Are there any studies out there that actually look at the TOTAL radiation doses you receive on a long haul flight rather than just cosmic which is just one type of radiation. The powers at be are more than happy to tell you that there is very little cosmic radiation on an aeroplane but are awfully quiet when it comes to total dosage.
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Old 10th Feb 2011, 07:19
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Are there any studies out there that actually look at the TOTAL radiation doses you receive on a long haul flight rather than just cosmic which is just one type of radiation. The powers at be are more than happy to tell you that there is very little cosmic radiation on an aeroplane but are awfully quiet when it comes to total dosage.
What other types of radiation do you have in mind? Essentially all of the additional radiation burden for people in airplanes at high altitude is ionizing radiation of extraterrestrial origin.
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Old 10th Feb 2011, 09:02
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What other types of radiation do you have in mind? Essentially all of the additional radiation burden for people in airplanes at high altitude is ionizing radiation of extraterrestrial origin.
So if you are at sea level you will receive the same amount of Gamma, Beta etc as you will in the same spot at 41000'?
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Old 10th Feb 2011, 11:04
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Hi, In B.A , as far as I know, we use a program based on the NASA/FAA CARI-6 software.
http://www.faa.gov/data_research/res...biology/cari6/

The company feeds in your monthly roster and it comes up with a monthly dose. It uses generic data for flights and not actual routes or flight levels.
Still, it is better than nothing, and I suppose it is the minimum that they could get away with without costing them any money.
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Old 10th Feb 2011, 14:31
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So if you are at sea level you will receive the same amount of Gamma, Beta etc as you will in the same spot at 41000'?
No, but that's precisely because the radiation comes from extraterrestrial sources (including the Sun). Most of the radiation is particle radiation (and most of that is protons), rather than electromagnetic, and the particles interact with the atmosphere, which diminishes their effects as one moves deeper and deeper into the atmosphere, with the least effect at sea level (or below).

Some of the radiation is electromagnetic, including the hard UV that comes from the Sun, most of which is also blocked by the atmosphere. This hard UV is a potential concern for pilots, since exposure to the short end of the spectrum may increase the risk of eye diseases such as macular degeneration. However, good sunglasses (and even some ordinary glasses) can block hard UV, and so may the windows of an aircraft. Even then, the brightness of the light at high altitude and the presence of strong light at the blue end of the spectrum might also contribute to eye disease (there's evidence that exposure to intense blue light can cause problems over time).

Anyway, all of this radiation is coming from outside the Earth. Depending on one's location, charged particles may be deflected by the Earth's own magnetic field, and both particles and electromagnetic waves are absorbed significantly by the atmosphere. Flights over the poles involve more radiation exposure because that's where the charged particles come streaming in, following the geomagnetic field (this has no effect on electromagnetic radiation, though).

I wonder from time to time about crew exposures to radiation, even though I'm not crew myself. As far as I know, there's no conclusive evidence that the extra radiation exposure produces increased morbidity or mortality among airline crews. It's something to think about and perhaps something to reduce if possible, but the risk is too small for the average crew member to worry about (there are greater risks to think about than radiation). A pilot can reduce his risk a lot more by sleeping for a full eight hours than by wearing lead underwear.
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Old 11th Feb 2011, 06:36
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I have always worried about the number of pilots who die within 5 years of retirement. Is is just to much jet lag that the body can bear, or is it radiation. It is known that pilots sometimes have a smaller sperm count than other males, is it radiation. It is known that female flight attendants have trouble getting pregnant (no they are not always married to pilots)! It was brought to the health authority in Australia during the years of the 747SP, that there were medical problems that were not obvious before. Makes you wonder.
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Old 11th Feb 2011, 23:28
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So back to original question if there is all this radiation out there that is penetrating the atmosphere why hasn't there been a study of the total radiation whilst flying and why do they only focus on one type of radiation? Or is the amount of other radiation so insignificant not matter?
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Old 12th Feb 2011, 05:31
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neville,

why hasn't there been a study of the total radiation whilst flying
I'm not sure why you are under the impression that is the case. The issue of elevated levels of radiation with increasing altitudes was noted in the early 20th century and has been the subject of (physics) research ever since. The Physics journals contain many studies - even articles the dread wiki gives some indication of the amount of research that has been undertaken over the years.

Without getting too bogged down in either stats or folklore surrounding this whole issue I'm another who feels that radiation is way down the list of things that are injurious to our flying health ( thinks disrupted sleep, irregular exposure to daylight, airline meals)
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Old 12th Feb 2011, 21:47
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I have just spent some time with a group of Nuclear Scientists who are specialist in Radiation and Contamination. These guys do this for a living and have designed and operated monitoring systems around the world. In short their credentials are impeccable. They tell me that our biggest concern should not be so called Cosmic Radiation per-se but contamination from man made particles present in the layers in which we operate in increasing amounts. These particles remain airborne for long periods and are fed into aircraft in the normal way and consumed by its occupants. Naturally we spend a great deal of time in the air and consequently absorb and concentrate comparatively high doses of this contamination. They have suggested that the only affective way to monitor this is to use a Dose Meter. Do any of you use such Dose Meters provided by your company??

Amongst other examples of why these levels are increasing they cited accidents in the old USSR which make Chernobyl look like a tea party. Vast, vast quantities of highly radioactive material was accidentally exploded into the atmosphere and surrounding areas. These materials were absorbed into the water courses and winter ice gradually being released in the summer as river levels drop, mud is exposed which turns to fine dust and is taken up into the atmosphere. A surprising amount ends up at high levels. Apparently this contamination is getting worse as river levels reduce due to over-use exposing more of the silty river deposits to the open air. Over a period of an hour or so these guys explained a terrifying scenario which is there now. They strongly recommended that any commercial pilot wear a Dose Meter to monitor individual absorption as a matter of urgency.
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Old 14th Feb 2011, 05:52
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Vast, vast quantities of highly radioactive material was accidentally exploded into the atmosphere and surrounding areas. These materials were absorbed into the water courses and winter ice gradually being released in the summer as river levels drop, mud is exposed which turns to fine dust and is taken up into the atmosphere.
So why would these particles be any more dangerous to pilots in the air than they were to everyone else while they were on the ground? In other words, since everyone is being exposed to them, what special risk do pilots and air crews run in comparison?

It's best not to get too worried about such things. There are many other hazards that are far more likely to kill cockpit and cabin crews over the course of their careers or thereafter.
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Old 16th Feb 2011, 09:14
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Current Research

I've just stumbled across this forum and i'm very interested in some of the posts. There is a lot of misinformation generally on this topic and plenty of debate even amoung the "informed".

I am a physicist working directly in this field so i'd just like to clarify a few fundamentals: the radiation dose received by aircrew (and some frequent flying passengers) is indeed typically higher than workers at nuclear power stations - this is in large part becuase their dose is much more closely monitored and controlled. It is true that the dose received is not something to panic about - typically two to three times the average UK annual background level - but it is not true to say that it is unimportant. European legislation recognises air crew as radiation workers and airlines typically apply rostering to avoid exceeding an operational threshold which would require them to apply regular health checking. The comparison with Medical radiation doses isn't particularly informative - yes, CT scans will give you more dose than all but the busiest pilot, but if you're in need of a CT scan then the enhanced cancer risk due to the scan is a trade-off against diagnosing whatever ailment you have. The same does not apply to the exposure of milliions of healthy passengers and crew. The measures in place for crew are better than nothing but balanced information should be provided to the flying public so they can make informed decisions about their own flying hours.

This all primarily relates to cosmic rays. The additional hazard from some types of solar flare has only recently started gathering momentum in terms of industry awareness. Radiation from the largest of these flares can not only cause personal dose to exceed some annual limits (though one of these has not occured for over twenty years) but they can also pose a threat to avionics via radiation effects on microelectronic components. The radiation environment is mixed and complex and most radiation dosimeters do not adequately measure the dose (this includes TLDs incidentally). Special consideration also needs to be given to pregnant passengers and crew.

Concorde was obliged to carry a monitor because of its high altitude, but in fact the dose on a subsonic flight between London and LA is higher than the dose on Concorde because of the higher latitude and greater duration. CARI-6 mentioned in another post, is a standard tool used for establshing dose on flights, but it is far from perfect and does not apply to solar flares. Research in this field is ongoing but awareness is poor.

Apologies for the lengthy post but I hope this clarifies a few things. For further information google "Advances in Measuring and Modeling the Atmospheric Radiation Environment" for a recent article and there are other papers. The European Cockpit Association published an open letter on this topic in September 2009 and this provides a reasonable summary.

I can provide further information to anyone who is interested - the more awareness this gets in the industry the better, especially as the legislation does not currently mandate any monitoring of frequent flying passengers.
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Old 18th Feb 2011, 20:42
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There really are a couple of interesting posts in this threat, nevertheless, I do want to clarify some important issues here.
It is very well established, that radiation causes effects on biologic systems. There are two distinctively different effects: stochastic and deterministic. Deterministic effects always will appear and cause damage to the living, ranging from radiation burns to failure of the immune system with subsequent death. Radiation burns of the skin are commonly seen in radiation therapy for tumors, and one of the aspects of radiation treatment planning is to keep this at an acceptable level. In former times, radiation burns were also frequently seen under fluorescopy, especially when performed by cardiologists for coronary angiography, but even this group of physicians lately has learned certain aspects of radiation protection. Deterministic radiation effects causing deaths can be seen during accidents, e.g. one of the helicopter pilots doing fire extinction work in tchernobyl was one of the unlucky. In general, deterministic radiation effects do not play a role for the general public and also not in conjunction with flying.
More complex are stochastic radiation effects, which do occur stochastically (well, the name does imply that). It is well established, that there is a pretty much linear dose response relationship for stochastic radiation effects for single doses above 100 mSv. This is known from the close monitoring of the survivors from Hiroshima and Nagasaki as well as from exposure especially in the early days of radiology.
Based from this data, the currently used concept is a linear interpolation into the low dose range, that is the dose range below 100 mSv (annual exposure is in the 1-3 mSv range, so even much lower). To make it quite clear, there is no study showing stochastic dose effects in this low dose range and there is no study showing no dose effects in this low dose range (an adequate study would need to randomize something like earths inhabitants against a second earth, which is a kind of difficult). All calculations of potential radiation deaths in this low dose range are from pure extrapolation.
Now, the big question is, is it scientifically acceptable to do a linear interpolation in this low dose range. Everybody who is honest can not say this. Summing up all the literature I know about this topic, the question remains open. There is some literature, which in fact does suggest that there is a linear dose response relation even in the lowest range. Other literature shows that very small doses do lead to a reduction of biologic effects. The pathomechanism being discussed for that is triggering of intracellular repair mechanisms, which thus also repair other below threshold damages on the DNA, therefore lowering potentially critical mutations. In addition, the low dose group of the A-bomb survivors in fact do not react in agreement with linear dose response relationship.
Thus it clearly is uncertain whether a low dose exposure to radiation has negative effects on your health or may be even positive effects. The current concept for diagnostic imaging is the so called ALARA (as low as reasonably achievable) principle, which in fact is a very practical an acceptable approach for low dose radiation exposure for medical indications. I would also act in that way for any other aspects, including flying. But there is also not at all reason to be overly critical, and calculating potential death rates for flights is just (un)scientific spin control.
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