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Space Forum / Shuttle / January 2005How much radiation?
After reading some recent reports mentioning ex astronauts now on ground duties, I wondered if there was some kind of exposure limit for those who have done long duration flights, at least in the US. I assume some record of radiation exposure for each is kept?? Brian  SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ >After reading some recent reports mentioning ex astronauts now on ground >duties, I wondered if there was some kind of exposure limit for those who >have done long duration flights, at least in the US. Yes, there is. As I understand it, NASA's radiation rules generally follow the recommendations of NCRP-98, "Guidance on Radiation Received in Space Activities", 1989, from the National Council on Radiation Protection and Measurements, although those are now thought to be a bit too generous for long-term exposures. Astronauts are legally radiation workers, so monitoring of doses, work rules that limit them, and efforts to keep them as low as possible, are legally mandatory. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net You are touching on a subject that is not pubicized that much. I find that any scientific research in space medicine that shows detrimental effects of spaceflight are not talked about too much. Matthew Ota > After reading some recent reports mentioning ex astronauts now on ground > duties, I wondered if there was some kind of exposure limit for those who [quoted text clipped - 3 lines] > > Brian > After reading some recent reports mentioning ex astronauts now on ground > duties, I wondered if there was some kind of exposure limit for those who [quoted text clipped - 5 lines] > > -- As noted Astronauts are legally radiation workers. I didn't even really consider this notion till I was reading Baxter's novel, "Voyage" where a member of the mission to Mars gets grounded and kicked off the flight because he'd been exposed too much to radiation while conducting multiple stints aboard a Skylab-type station used in lunar orbit. I'm noticing that with the exception of Mike Foale none of the Shuttle-Mir Astronauts (granted, except Foale, only a couple are still active, Andy Thomas and Dave Wolf) or NASA members of ISS expeditions have been assigned to follow up ISS expeditions. Not even for crews down the road yet. This due to some legallity regarding radiation exposure or does the Astronaut Office just want to give everyone a shot at a stint aboard ISS? -A.L. >I'm noticing that with the exception of Mike Foale none of the >Shuttle-Mir Astronauts (granted, except Foale, only a couple are still [quoted text clipped - 3 lines] >exposure or does the Astronaut Office just want to give everyone a shot >at a stint aboard ISS? There *are* career limits on exposure, but I suspect this is mostly just a matter of the overstaffed astronaut corps and a philosophy of giving everybody a turn. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net > After reading some recent reports mentioning ex astronauts now on ground > duties, I wondered if there was some kind of exposure limit for those who [quoted text clipped - 3 lines] > > Brian I've looked for the same info many years ago. I don't remember the source, but numbers in the tens of Rads on one Apollo flight. Legal limits have nothing to do with medical reality, only political. Anyway, the health risks due to launch and landing far exceed any radiation health risk. >> After reading some recent reports mentioning ex astronauts now on ground >> duties, I wondered if there was some kind of exposure limit for those who [quoted text clipped - 9 lines] > Anyway, the health risks due to launch and landing far exceed any > radiation health risk. No, I disagree. You are talking death, I'm talking health issue like Cancer or problems with sperm or conceiving. Brian SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ >>> After reading some recent reports mentioning ex astronauts now on ground >>> duties, I wondered if there was some kind of exposure limit for those who [quoted text clipped - 12 lines] > No, I disagree. You are talking death, I'm talking health issue like Cancer > or problems with sperm or conceiving. I posted the abstract of a paper studying the effects on eyesight to sci.space.history the other day... hmm... Space radiation and cataracts in astronauts Cucinotta FA, Manuel FK, Jones J, Iszard G, Murrey J, Djojonegro B, Wear M RADIATION RESEARCH 156 (5): 460-466 Part 1 NOV 2001 "...These results, while preliminary because of the use of subjective scoring methods, suggest that relatively low doses of space radiation are causative of an increased incidence and early appearance of cataracts." Signature-Andrew Gray andrew.gray@dunelm.org.uk >I've looked for the same info many years ago. I don't remember the source, >but numbers in the tens of Rads on one Apollo flight... No, the highest exposure on an Apollo lunar expedition was a skin dose of 1.14 rad on Apollo 14. The Skylab 4 crew took 7.74 rads (mean TLD dose) in their 90-day flight. That's the highest dose on any pre-Challenger flight (the work for NCRP-98 was done in the post-Challenger hiatus) which had good monitoring (data for Mercury and Gemini flights is limited). >Legal limits have nothing to do with medical reality, only political. Legal limits in most places actually track the current state of medical knowledge of radiation effects reasonably well. There is inevitably a certain amount of value judgement involved -- there is no such thing as perfect safety, so one must always decide how much risk is too much -- but political interference has been surprisingly slight. >Anyway, the health risks due to launch and landing far exceed any radiation >health risk. NCRP-98 specifically recommends astronaut career limits based on a 3% risk of excess cancer mortality -- roughly comparable to the lifetime risk of fatal accidents in moderately-dangerous occupations -- with the caveat that for exploration missions, which have considerable and poorly-known risks of their own, the limits should be considered guidelines only. Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net >>I've looked for the same info many years ago. I don't remember the >>source, [quoted text clipped - 5 lines] > flight (the work for NCRP-98 was done in the post-Challenger hiatus) which > had good monitoring (data for Mercury and Gemini flights is limited). Ok. The number that was in my head was "14" What I thought remembered was the listing of all Apollo flights and that just one flight had a higher exposure than all the others. I'll look up NCRP-98. >>Legal limits have nothing to do with medical reality, only political. > [quoted text clipped - 13 lines] > that for exploration missions, which have considerable and poorly-known > risks of their own, the limits should be considered guidelines only. Much better answer than mine, thnx. How is "3% risk of excess cancer mortality" quantified? I'm sure that statistics are involved and that the "3%" part was decided politically. > "Think outside the box -- the box isn't our friend." | Henry Spencer > -- George Herbert | > henry@spsystems.net >> No, the highest exposure on an Apollo lunar expedition was a skin dose of >> 1.14 rad on Apollo 14... > >Ok. The number that was in my head was "14" What I thought remembered was >the listing of all Apollo flights and that just one flight had a higher >exposure than all the others. Yep. For some reason -- unfavorable trajectory or bad solar activity -- Apollo 14 got two or three times the average dose of the other Apollos. >I'll look up NCRP-98. I see NCRP is online now, at <http://www.ncrponline.org/>, but by the looks of it, their reports are still paper-only and still cost money. >> NCRP-98 specifically recommends astronaut career limits based on a 3% risk >> of excess cancer mortality -- roughly comparable to the lifetime risk of >> fatal accidents in moderately-dangerous occupations... > >Much better answer than mine, thnx. How is "3% risk of excess cancer >mortality" quantified? We now have a fair idea of how the probability of radiation-caused cancer scales with effective dose, mostly from the ongoing studies of the Hiroshima and Nagasaki survivors. The one tricky part is converting from absorbed dose (which is physics) to effective dose (which is biology) -- going from rads to rems in traditional radiation units, or grays to sieverts in SI -- which is different for different types of radiation. The exposure limits are currently in sieverts. >I'm sure that statistics are involved and that the "3%" part was decided >politically. NCRP is a scientific group, not a political one. There may have been some politics in the choice of the exact number, but there's a long pattern of radiation standards being set based on risks in moderately-dangerous non-radiation occupations(*) -- whose range is around 2-5% -- so 3% is not grossly out of line. (* "Moderately dangerous" means a job with significant on-the-job risk, e.g. construction or agriculture, but excluding the really high-risk ones like lumberjack or deep-sea fisherman or test pilot. ) Signature"Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | henry@spsystems.net |
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