In-Flight Radiation

[ROBBARISH@aol.com]

David Lee wrote:
<begin excerpt>
OSHA may possibly have some regulatory authority in this area.  Taking Rob 
Barish's point that flight crew members are unquestionably "radiation 
workers" and the empowered regulatory entity is the FAA, then it appears that 
Rob's point is that the FAA is not asserting itself appropriately as far as 
the radiation monitoring of flight crew members is concerned.

But If the FAA were to assert itself to a greater regulatory 
degree, what might be the result?  As far as I can discern under such a 
hypothetical, the FAA would formally declare flight crew members to be 
"radiation workers" in which case the relevant annual dose limit would 
probably something in the neighborhood of 5 rem--far above the 100 mrem/yr 
"member of the public" dose limit.  Then the only remaining issue would be 
that of providing individual dosimetry to those crew members judged likely to 
exceed 0.5 rem/yr.  Perhaps Sandy Perle can elucidate, but as far as I have 
been able to discern, even if the FAA were to require individual dosimetry 
for at least a portion of flight crew members, earth-based NVLAP individual 
dosimetry systems are not presently certified for assessing with reasonable 
accuracy the much different (mixed field) radiation environment to which 
flight crew members are exposed.

As others have already pointed out, from a radiation safety standpoint, 
flight crew member doses may already be ALARA, even in the absence of greater 
FAA regulatory assertiveness, given that basically only the precept of "time" 
can be used to reduce crew member radiation doses.  The external radiation 
safety precepts of "distance" and "shielding" are impractical in the case of 
flight crew members. So even if some governmental regulatory agency were to 
bring flight crew members into the "radiation worker" fold and health 
physicists to set themselves to the task of documenting and trying to reduce 
crew member doses to ALARA, how would flight crew members end up being better 
protected compared to the present situation?

In the end, as already stated by Al Tschaeche, we are back to the 
issue of "low doses."  Even if the average flight crew member dose is say 0.6 
rem/yr, 600 mrem/yr is simply not a radiobiologically harmful dose, despite 
the fact that within an L-NT regulatory framework, 600 mrem/yr impels a 
radiological control organization to manifest some degree of ALARA (dose 
bookkeeping) concern.<end excerpt>

Regarding David's impression that dose monitoring of flight crews is of 
concern to me, it is fair to say that it is the lack of education of this 
worker group that is of far greater concern. I am not really as bothered by 
failure to institute dose monitoring (except for pregnant crewmembers) as I 
am by the failure of the FAA to require their regulated employer group (the 
airlines) to even mention this subject to the flight attendants and pilots. 
As I said earlier, the advisory circular AC 120-61 on crewmember training is 
completely voluntary, and no airline has chosen to follow its advice and 
institute such training. I think this is regrettable. As I also said in an 
earlier posting, a dose of 5-6 mSv (500-600 mrem) per year for a twenty or 
thirty year career will bring the accumulated lifetime dose to these people 
above the "10 rem lifetime" dose that the HPS considers a boundary of concern 
for real health risks. As David implied later in his note, failure to 
regulate, even at the level of providing some basic educational material for 
this large worker group, is certainly out of whack with respect to the 
elaborate radiation training programs in current practice for workers 
receiving a small fraction of crewmembers doses.

Let me again state unequivocally that the FAA has classified their regulated 
constituency, flight crewmembers, as radiation workers. The have advised that 
the employers educate them with AC 120-61.  They feel that their creation of 
the CARI computer program, which is accessible to anyone who is interested, 
should serve as the mechanism for dose assessment for any interested 
crewmember. I can state this latter claim to be factual since I am in 
possession of a letter from Thomas E. McSweeny, Associate Administrator for 
Regulation and Certification of the FAA, dated 16 July 1999, in which he 
states "The agency has also made available educational materials and a 
computer program that permits crewmembers to calculate their personal 
radiation exposure. While there is an increased risk for cancer from any 
ionizing radiation exposure, air carrier crewmembers are unlikely to exceed 
the recommended exposure limits of the Environmental Protection Agency 
because of cosmic radiation. Only pregnant flight attendants could approach 
these limits but the use of exposure calculations combined with appropriate 
flight scheduling can effectively mitigate the risk."

At this point it is appropriate to allow you all to download the famous CARI 
program in its latest version so that you can see how the agency expects the 
worker to perform these "exposure calculations." After you do so, imagine 
that you are a 20-year-old flight attendant who is interested in determining 
her dose. See what the FAA expects her to do on her PC. By the way, once you 
log on don't forget to look up the appropriate heliocentric potential from 
the FAA web site, because the program won't run without it. Go to:
www.cami.jccbi.gov and give yourself a thrill.

Addressing David's last point, about ALARA, as I said in one of my earlier 
postings, no flight crewmember is likely to exceed the 50 mSv (5 rem) annual 
dose limit. This is the limit referred to by Mr. McSweeny in the quote above. 
As far as I am concerned, receiving these occupational exposures, with their 
potential for a lifetime accumulation greater than 100 mSv, is best left to 
the crewmembers themselves but such a decision cannot be made without some 
understanding of the subject and discussion of the risks. That's where the 
current situation is so unfortunate. A large body of workers regularly 
receives these occupational exposures, and they are completely unaware of the 
situation and therefore unable to make an informed decision as to the 
acceptability of the risk. Even if all of us agree that the risk is small, we 
should also agree that these people have the right to decide for themselves 
if it is acceptable.  
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