space radiation - umd
TRANSCRIPT
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
Space Radiation• Sources of radiation• Biological effects• Approaches to shielding• Probabilistic estimation• Spacecraft shielding design• Recent revisions to understanding radiation effects
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© 2017 David L. Akin - All rights reserved http://spacecraft.ssl.umd.edu
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Issues of Human Radiation Exposure• Acute dosage effects• Carcinogenesis • Central nervous system effects• Chronic and degenerative tissue risks
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The Origin of a Class X1 Solar Flare
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Solar Radiation• Produced continuously (solar wind)• Increases dramatically during solar particle events
(SPEs) – Coronal ejections– Solar flares
• Primarily high-energy electrons and protons (10-500 MeV)
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Image of Galaxy in Gamma Rays
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Galactic Cosmic Rays• Atomic nuclei, stripped of electrons and
accelerated by supernova explosions to nearly the speed of light
• Constituents:– 90% protons– 9% alpha particles– 1% heavier elements
• Ionization potential proportional to square of charge (Fe26+=676 x p+)
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Radiation in Free Space
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Radiation Damage to DNA
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Radiation Units• Dose D= absorbed radiation
• Dose equivalent H= effective absorbed radiation
• LET = Linear Energy Transfer <KeV/µ m>
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1 Gray = 1Joule
kg= 100 rad = 10, 000
ergs
gm
1 Sievert = 1Joule
kg= 100 rem = 10, 000
ergs
gm
H = DQ rem = RBE � rad
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Radiation Quality Factor
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Radiation QX-rays 1
5 MeV γ-rays 0.51 MeV γ-rays 0.7
200 KeV γ-rays 1Electrons 1Protons 2-10
Neutrons 2-10α-particles 10-20
GCR 20+
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Symptoms of Acute Radiation Exposure• “Radiation sickness”: headache, dizziness, malaise,
nausea, vomiting, diarrhea, lowered RBC and WBC counts, irritability, insomnia
• 50 rem (0.5 Sv)– Mild symptoms, mostly on first day– ~100% survival
• 100-200 rem (1-2 Sv)– Increase in severity and duration– 70% incidence of vomiting at 200 rem– 25%-35% drop in blood cell production– Mild bleeding, fever, and infection in 4-5 weeks
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Symptoms of Acute Radiation Exposure• 200-350 rem (2-3.5 Sv)
– Earlier and more severe symptoms– Moderate bleeding, fever, infection, and diarrhea at 4-5
weeks• 350-550 rem (3.5-5.5 Sv)
– Severe symptoms– Severe and prolonged vomiting - electrolyte imbalances– 50-90% mortality from damage to hematopoietic system
if untreated
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Symptoms of Acute Radiation Exposure• 550-750 rem (5.5-7.5 Sv)
– Severe vomiting and nausea on first day– Total destruction of blood-forming organs– Untreated survival time 2-3 weeks
• 750-1000 rem (7.5-10 Sv)– Survival time ~2 weeks– Severe nausea and vomiting over first three days– 75% prostrate by end of first week
• 1000-2000 rem (10-20 Sv)– Severe nausea and vomiting in 30 minutes
• 4500 rem (45 Sv)– Survival time as short as 32 hrs - 100% in one week
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Long-Term Effects of Radiation Exposure• Radiation carcinogenesis
– Function of exposure, dosage, LET of radiation
• Radiation mutagenesis– Mutations in offspring– Mouse experiments show doubling in mutation rate at
15-30 rad (acute), 100 rad (chronic) exposures
• Radiation-induced cataracts– Observed correlation at 200 rad (acute), 550 rad (chronic)– Evidence of low onset (25 rad) at high LET
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Radiation Carcinogenesis• Manifestations
– Myelocytic leukemia– Cancer of breast, lung, thyroid, and bowel
• Latency in atomic bomb survivors– Leukemia: mean 14 yrs, range 5-20 years– All other cancers: mean 25 years
• Overall marginal cancer risk– 70-165 deaths/million people/rem/year– 100,000 people exposed to 10 rem (acute) -> 800
additional deaths (20,000 natural cancer deaths) - 4%
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Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 16Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 17Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
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NASA Radiation Dose Limits
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SPE and GCR Shielding
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Shielding Depth, g/cm20 5 10 15 20 25 30 35
Dose
Equ
ivalen
t, rem
/yr
1
10
100
1000
10000GCR L. HydrogenGCR PolyethyleneGCR GraphiteGCR AluminumGCR RegolithSPE GraphiteSPE RegolithSPE L. Hydrogen
August 1972 SPE and GCR Solar Min
Francis Cucinotta, “What’s New in Space Radiation Risk Assessments for Exploration” NASA Future In-Space Operations Telecon, May 18, 2011
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Density of Common Shielding
20
0
2
4
6
8
10
12
Polyethyle
neWate
rGr/E
p
Acrylic
s
AluminumLea
d
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Comparative Thickness of Shields
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0
1
2
3
Polyethyle
neWate
rGr/E
p
Acrylic
s
AluminumLea
d
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Comparative Mass for Shielding
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0
1
2
3
4
5
Polyeth
ylene
Water
Gr/Ep
Acrylics
Aluminu
mLe
ad
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Shielding Materials and GCR
2325
MaterialE (Sv)
Solar Minimum SPE + Solar Maximum
10 g/cm2
Liquid H2 0.40 0.19Liquid CH4 0.50 0.30Polyethylene 0.52 0.33Water 0.53 0.35Epoxy 0.53 0.36Aluminum 0.57 0.43
20 g/cm2
Liquid H2 0.36 0.16Liquid CH4 0.45 0.22Polyethylene 0.47 0.24Water 0.48 0.25Epoxy 0.49 0.26Aluminum 0.53 0.30
40 g/cm2
Liquid H2 0.31 0.15Liquid CH4 0.43 0.21Polyethylene 0.46 0.23Water 0.46 0.23Epoxy 0.48 0.24Aluminum 0.51 0.26
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Effective Dose Based on Shielding
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Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
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Shielding Materials Effect on GCR
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–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Lunar Regolith Shielding for SPE
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–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Mars Regolith Shielding Effectiveness
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–, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
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Radiation Exposure Induced Deaths
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Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
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3% Risk (REID)
6% Risk (REID)
95% CL 90% CL 95% CL 90% CLAge, y Males35 140 184 290 36145 150 196 311 39255 169 219 349 439Age, y Females35 88 116 187 23245 97 128 206 25555 113 146 234 293
Number of Days in Deep Space At Solar Minimum at 20 gm/cm2 shielding with a 95% or 90% confidence level to be below 3% or 6% REID (Avg US pop)
Deep Space Mortality Risks from
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SPE and GCR Shielding
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Francis Cucinotta, “What’s New in Space Radiation Risk Assessments for Exploration” NASA Future In-Space Operations Telecon, May 18, 2011
Confidence Levels for Career Risks on ISSEXAMPLE: 45-yr.-Old Males; GCR and trapped proton exposures
Solar Max
Days on ISS0
(%) C
onfid
ence
tobe
bel
ow c
aree
r lim
it100
Current Uncertainties With Uncertainty Reduction
50
60
70
80
90
250 500 750 1000 250 500 750 1000
Days on ISS
Solar Max
Solar MinSolar Min
SAFE ZONE
45-Year Old Male: GCR and Trapped Proton Exposure
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U N I V E R S I T Y O FMARYLAND 31Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 32Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 33Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 34Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 35Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 36Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 37Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 38Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
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U N I V E R S I T Y O FMARYLAND 39Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
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U N I V E R S I T Y O FMARYLAND 40Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
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U N I V E R S I T Y O FMARYLAND 41Francis Cucinotta, “What’s New in Space Radiation Research for Exploration?” NASA FISO, May 18, 2011
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U N I V E R S I T Y O FMARYLAND 42Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 43Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 44Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 45Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 46Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND 47Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA FISO, Oct 31, 2012
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NewEstimatesofRadiationsRisksareFavorableforMarsExploration:HoweverMajorScientificQuestionsRemainUnanswered
Francis A. CucinottaUniversity of Nevada, Las Vegas NV, USA
FutureIn-SpaceOperations(FISO)colloquium (July 13, 2016)
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Acknowledgements
• Funding:UniversityofNevada,LasVegas• UNLV:MuratAlp,ElliedonnaCacao
Outline
• Introduction• RadiationLimitsforAstronauts• CancerRiskEstimatesforDeepSpace• UnansweredScienceQuestionsinCancerRisks• Conclusions• BackupMaterialonSpaceEnvironmentsandShielding
49Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
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Introduction to Space Radiation and Exploration
Spaceradiationisamajorchallengetoexploration:• Risksarehighlimitingmissionlengthorcrewselectionwithhighcosttoprotectagainstrisksanduncertainties
• Pastmissionshavenotledtoattributablerad-effectsexceptforcataracts,howeverforaMarsmissionmostcancersobservedwouldbeattributabletospaceradiation
Approachtosolvetheseproblems:• ProbabilisticriskassessmentframeworkforSpaceMissionDesign
• Hypothesis&Ground-basedresearch• MedicalPolicyFoundationsforSafety
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Cosmic Ray Health Risks
• Risks:• AcuteRadiationSyndromes(ARS)
• Cancer• Cataracts• CentralNervousSystemEffects• CirculatoryDiseases• Othernormaltissueeffects
• Focus:HighChargeandEnergy(HZE)particleshaveuniquetrackstructuresleadingtoquantitativeandqualitativedifferencesinbiologicaleffectscomparedtoγ-rays.
CataractsinAstronauts
Time after first-mission, yr
5 10 15 20 25 30
Low-dose AstronautsHigh-dose Astronauts
Time after first-mission, yr
0 5 10 15 20 25 30
Pro
babi
lity
of C
atar
act
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Low-dose AstroanautsHigh-Dose astronauts
All Cataracts Non-trace Cataracts
Probability of Cataracts after Space Flight
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
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Space Radiation Safety Requirements
• CongresshascharteredtheNationalCouncilonRadiationProtectionandMeasurements(NCRP)toguideFederalagenciesonradiationlimitsandprocedures
• SafetyPrinciplesofRiskJustification,RiskLimitationandALARA(aslowasreasonablyachievable)
• Crewsafety• limitof3%fatalcancerriskbasedon1989comparisonofrisksin“unsafe”industries
• NASAlimitsthe3%lifetimefatalityriskata95%confidenceleveltoprotectagainstuncertaintiesinriskprojections
• PlaceholderrequirementsinPELlimitCentralNervousSystem(CNS)andcirculatorydiseaserisksfromspaceradiation
• LimitssetMissionandVehicleRequirements• shielding,dosimetry,countermeasures,&crew
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Requirements to Limit Radiation Mortality
• TheNationalCouncilonRadiationProtectionandMeasurements(NCRP)isCharteredbytheU.S.CongresstoguideGovt.AgenciesonRadiationSafety.
• In1989,NCRPrecommendedageatexposureandgenderbaseddoselimitsusinga3%fatalcancerriskasbasisfordoselimits(<1in33probabilityofoccupationaldeath).
• TheNCRPConsideredcomparisonstoaccidentaldeathsintheso-called“Safe”,“Less-Safe”and“Unsafe”IndustriesandconcludedDoseLimitsshouldlimitrisksimilarto“Less-safe”Industries.
• TheNCRPnotedthatsinceAstronautsfaceotherriskssimilarto“unsafe”industriesitwouldbeinappropriateforNASA’sradiationlimitstobesimilartorisksin“unsafe”industries.
• HoweverSafe,LessSafeandUnsafeIndustryriskscontinuetodecline.
53Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Occupation AnnualFatalAccidentRateper100,000workers
(%LifetimeFatalityfor45-ycareer)1987a 1998b 2009c
SafeManufacturing 6(0.27%) 3(0.14) 2(0.1)Trade 5(0.23) 2(0.1) 4.3(0.2)Services 5(0.23) 1.5(<0.1) 2(0.1)Government 8(0.36) 2(0.1) 1.8(<0.1)LessSafeAgriculture 49(2.2) 22(1.0) 25.4(1.1)Mining 38(1.7) 24(1.1) 12.8(0.58)Construction 35(1.6) 14(0.63) 9.3(0.42)Transportation 28(1.3) 12(0.54) 11(0.5)ALL 10(0.45) 4(0.18) 2.8(0.13)
Annual Fatality Rates from Accidents in Different Occupations noted by NCRP Report 98 (1989)a, NCRP Report 132 (2000)b, and recent values from National Safety Councilc. Percent probabilities for occupational fatality for careers of 45 years are listed in parenthesis.
Risk in Less-Safe Industries have decreased to <1%
54Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Alternative Comparative Risk Basis?• CurrentLossofCrew(LOC)riskforSpaceflightis1in270accordingtoNASA.
• AerospaceSafetyAdvisoryPanel(ASAP)recommendsNASAcanmakeinvestmentstoreduceLOCtolessthan1in750.
• TheLife-LossforRadiationDeathfromGamma-rayinducedcancersisestimatedat15-yearsforNever-smokerscomparedto40yearsforLOC.
• Life-LossforGCRishigherthangamma-rays.• Isthe1in33radiationlimitcomparabletoLOC(1in270)probabilitywhenadjustedforlife-loss?(ethics,euthanasia?)
• RisktoFiremanorsoldiersinIraqiwarzonesoldiers~0.5%• Note:Leadershipisfindingsolutionstospaceradiationproblem,whilewaivingradiationlimitsisnotleadership.
55Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Mean Life-loss for Equivalent γ-ray exposure if Radiation Death Occurs for 18-months on ISS
(Female and Male Never-smokers)Tissue HT,Svor
Gy-EqLLE,y
Leukemia,Sv 0.151 23.1Stomach 0.235 16.3Colon 0.261 16.7Liver 0.229 13.5Bladder 0.231 11.2Lung 0.264 13.2Esophagus 0.249 15.1OralCavity 0.308 15.3Brain-CNS 0.286 18Thyroid 0.308 22Skin 0.282 11.8Remainder 0.264 12Breast 0.289 15.7Ovarian 0.241 17.9Uterine 0.241 17.1TotalCancer 0.244 15CVD,Gy-Eq 0.182 9.1IHD 0.182 9.5
Tissue HT,SvorGy-Eq
LLE,y
Leukemia,Sv 0.145 22.1Stomach 0.227 15.6Colon 0.251 16.4Liver 0.235 14Bladder 0.224 10.9Lung 0.245 13.6Esophagus 0.242 14.9OralCavity 0.261 15.8Brain-CNS 0.279 17Thyroid 0.261 20.8Skin 0.308 12Remainder 0.253 11.7Prostate 0.260 11.5TotalCancer 0.228 15CVD,Gy-Eq 0.174 9.8IHD 0.174 10.6
CVD=Cardiovascular disease, IHD=Ischemic Heart disease56
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Uncertainties in Space Radiobiology Require New Knowledge and Approaches
•NCRPReports98,132,152notedriskestimateswerehighlyuncertainforGalacticCosmicRays(GCR).–UncertaintiestoolargeforEarthbasedmethodstobeappliedtoGCR
–NRCReportsin1996,1999and2008echotheseconcerns•Allexpertsagreethatknowledgeislimited:
–Unlikeotherdisciplineswherethefundamentalphysiologicalbasisofspaceflightbiomedicalproblemsislargelyknown,thescientificbasisofHZEparticleradiobiologyislargelyunknown
–DifferencesbetweenbiologicaldamageofHZEparticlesinspacevs.x-rays,limitsEarth-baseddataonhealtheffectsforspaceapplications
57Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
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NASA Space Cancer Risk (NSCR) Model- 2012
• ReviewedbyU.S.NationalAcademyofSciences(NAS)
• 95%ConfidencelevelforLimitof3%RadiationExposureInducedDeath(REID)
• Notconservativeduetonon-cancerrisksyettobeevaluated
• Radiationqualitydescribedusingtrackstructuretheory
• PDF’sforuncertaintyevaluation• LeukemialowerQthanSolidcancer
• RedefinedagedependenceofriskusingBEIRVIIapproach
• UNSCEARLowLETRiskcoefficients• RisksforNever-Smokerstorepresenthealthyworkers
GCRdosesonMars
GCRdominateISSorganrisk
Z*2/β2
1 10 100 1000 10000
d(%
RE
ID)/d
(Z*2
/β2 )
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Solid CancerLeukemia
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Space Radiation Environments• Galacticcosmicrays(GCR)penetratingprotonsandheavynuclei;abiologicalsciencechallenge
• shieldingisnoteffectiveduetosecondariesinshieldingandtissue
• largebiologicaluncertaintieslimitsabilitytoevaluaterisksaccurately
• Uncertaintiescloudunderstandingofeffectivenessofpossiblemitigations
• SolarParticleEvents(SPE):lowtomediumenergyprotons
• shieldingiseffective;optimizationneededtoreduceweight
• accurateeventalert,dosimetryandresponsesareessentialforcrewsafety
• improvedunderstandingofradiobiologyneededtoperformoptimization
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• GCR dose and SPE probability are anti-correlated over 11-year solar cycle. • Hsolid is Organ Dose Equivalent for Solid cancer risks • Lines show times for 43 largest of ~400 SPE’s since 1950 (organ doses >10 mGy)
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Comparison of MSL RAD Measurements to NASA Space Cancer Risk Model (NSCR-2012):
Comparison GCRDoseRate(mGy/day)
GCRDoseEquiv.Rate(mSv/day)
ModelCruisetoMars 0.445 1.80RADCruisetoMars(Zeitlinetal.2013)
0.481+0.08 1.84+0.33
ModelMarssurface(Kimetal.2014)
0.20 0.72
RADMarsSurface(Hassleretal.2014)
0.205+0.05 0.70+0.1760
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Reference Population for Astronauts?
• AllprioranalysisusedtheAverageU.S.Populationasthereferencepopulationforastronauts.
• OurCancerriskmodelintroducedsomeaspectsofhealthworkereffectforriskprojections.
• adaptedbyNASAafterNASreviewin2012
• Astronautsshouldbeconsideredas“healthyworkers”,whichcouldmodifyriskestimates.
• LowercancerrisksmayoccurduetoimprovedBMI,exercise,diet,orearlydetectionfromimprovedhealthcarecomparedtoU.S.Average
• Morethan90%ofastronautsarenever-smokersandothersformersmokers
• Healthyworkereffectsaredifficulttoquantifywiththeexceptionofcancerratesfornever-smokers.
• RevisedNASAprojectionmodelstoconsiderestimatesofradiationrisksfornever-smokers
61Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Healthy Worker Effects in Astronauts (N=339)(Cucinotta et al. 2013)
62NS = Never-Smoker; NW = Normal WeightFrancis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Astronauts live very long due to low Circulatory Disease --even with low space doses (ave. 40 mSv)
Comparison SMRAstronauts vs. U.S. avg. 0.60 [0.34, 1.06]Astronauts vs. NS avg. 1.13 [0.64, 1.99]Astronauts vs NW avg. 0.60 [0.34, 1.05]Astronauts vs NS-NW Avg. 1.24 [0.70, 2.18]
Standard Cancer Mortality Ratio (SMR) for astronauts relative to other populations for Cancer
Comparison SMRAstronauts vs. U.S. avg. 0.33 [0.14, 0.80]Astronauts vs. NS avg. 0.43 [0.18, 1.04]Astronauts vs NW avg. 0.47 [0.19, 1.12]Astronauts vs NS-NW Avg. 0.67 [0.28, 1.62]
SMR for astronauts for Circulatory diseases
NS = never-smoker, NW = Normal Weight 63Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
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Major Sources of Uncertainty
• Radiationqualityeffectsonbiologicaldamage(RBE–QF)• QualitativeandquantitativedifferencesofSpaceRadiationcomparedtox-rays
• Dependenceofriskondose-ratesinspace(DDREF)• BiologyofDNArepair,cellregulation
• Predictingsolarevents• Onset,temporal,andsizepredictions
• Extrapolationfromexperimentaldatatohumans
• Individualradiation-sensitivity• Genetic,dietaryand“healthyworker”effects
Nature Rev. Cancer (2008)
17Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
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Fundamental Issue of Types of Radiation
• The ionizations and excitations in cells and tissue that occur are not distributed at random.
• They are stochastically produced but localized along the track of the incoming radiation.
• The pattern of this localization depends on the type of radiation involved.
• This means that different types of radiation will deposit different amounts of energy in the same space.
• The description of energy deposition at microscopic level is called Microdosimetry or Track Structure
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
The Dose and Dose-Rate Reduction Effectiveness Factor (DDREF)
• DDREFreducescancerriskestimates.
• DDREFestimatefromA-bombsurvivorsis1.3inNationalAcademyofScienceBEIRVIIReport.
• DDREFestimatefromanimalexperiments2to3.
66
BayesianAnalysisusingBEIRVIIPriorDistributionandmousedata
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
NASA Radiation Quality Function (NQF)-2012
• InternationalbodiesuseQFdependentonLETalone.• TrackstructureconceptsandexistingradiobiologydatausedtoguidechoiceonfunctionalformsforQF:
• MaximumeffectivenessperparticlecanbeestimatedbyexperimentsforRBEmaxandoccursat“saturationpoint”ofcrosssectionforanyZ
• Delta-rayeffectsforrelativisticparticlesaccountedforinQFmodel;higherZlesseffectiveatfixedLETcomparedtolowerZ
• PDFsaccountforvariationofthreeparametersvalues:(Σ0/αγ,m,andκ)basedonexistingbutlimitedradiobiologydata.PTDlowenergycorrection.Qmax~ Σ0/αγ
),(
)/(24.6)),(1( 0 EZP
LETEZPQNASA
γαΣ+−=
TD
m PZEZP ))/exp(1(),( 22* κβ−−=
67Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Uncertainty Analysis
• Monte-Carlouncertaintyanalysisusesriskequationmodifiedbynormaldeviatesthatrepresentpossiblevaluesforkeyfactorsthatenterrepresentedbyprobabilitydistributionfunctions(PDF):
• defineX∈R(x)asarandomvariatethattakesonquantilesx1,x2,…,xnsuchthatp(xi)=P(X=xi)withthenormalizationconditionΣp(xi)=1.
• C(xi)isdefinedasthecumulativedistributionfunction,C(x),whichmapsXintotheuniformdistributionU(0,1),
• DefinetheinversecumulativedistributionfunctionC(x)-1toperforminversemappingofU(0,1)intox:x=C(x)-1
• PDFforQF,DDREF,Low-LETcancerrate,Organdose,etc.• ForaMonte-Carlotrial, ξ,RiskRateislike
0
0 ( , )R
R phys Q
D
x x xFLQRisk R age gender
DDREF xξ
ξ
⎧ ⎫⎪ ⎪= ⎨ ⎬
⎪ ⎪⎩ ⎭68
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Risk for Exploration (Cucinotta et al. 2013) Cancer and Circulatory Disease
ISS = International Space Station; lower risk because GCR partially shielded By Earth Shadow and Magnetic Field Circulatory disease estimate from human data on Stroke and Ischemic Heart disease
69Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
PC = Probability of Causation at 10 years Post-exposure in these Calculations. If cancer is discovered In astronaut probability Radiation was the cause
70Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Redefining QFs to Reduce Uncertainty
• QF’sarebasedonRBEmaxthatintroducesuncertaintyoflowdose-rategamma-rays.
• NSCR-2015redefinesQF’sagainstRBEforacutegamma-raysathigherdosesforsolidtumorsinmice.
• Numerousexperimentsshownodose-rateeffectathighLETforexposuretimes<2weeks
• BayesiananalysisusedtocorrelateDDREFformatchedsolidtumordata.
• Lowersriskanduncertaintyestimatesby25%and35%,respectively.
71Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
NSCR Revision : Track Structure Approach: “core” and “penumbra” in Biological Effects
),(
)/(24.6)),(1( 0 EZP
LETEZPQNASA
γαΣ+−=
),(),(),(EZQ
DDREFEZQ
DDREFEZQF
highlowAcute +=γ
72Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Lack of dose-rate effect for heavy ions
73
Incidence of HCC (%) following Acute or Fractionated Exposures of 600 MeV/nucleon 56Fe Ions (Ullrich, Weil et al.)
0
10
20
30
40
50
60
0.2GyFeAcute 0.2GyFe3Fx 0.2GyFe6Fx
48hoursbetweenfractionsabout300micepergroup. 33
Harderian Gland Tumors following acute or fractionated Titanium Exposures in B6CF1 mice
(Blakeley, Chang et al. 2015)
33
0
Acute 0.13 Gy
5 FN 0.13 Gy
Acute 0.26 Gy
5 FN 0.052 Gy
% P
revalence
0
10
20
30
40
5fractionsat24hintervals
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Tumor Model Sex Radiation, RBEmax DDREF RBEγAcuteHarderianGland* B6CF1mice F Fe,180(600MeV/u) 39.6+11.5
2728
--
2.17+1.1
--14
HarderianGland B6CF1mice F ArSOBP**,~200 27 - -Heptocellularcarconoma
CBAmice M Fe,155(1GeV/u) NotEstimated - 50.9+9.9
Heptocellularcarconoma
C3H/HeNCrlmice M Fe(600MeV/u),175 NotEstimated - 66.9+41.1
Heptocellularcarconoma
C3H/HeNCrlmice M Si,(300MeV/u),70 NotEstimated - 73.5+46.6
Lung BALB/cmice F Fissionneutrons 33+12 2.8 11.8Mammary Balbcmice F Fissionneutrons 18.5+6 1.9 9.7Pituitary RFMmice F Fissionneutrons 59+52 2.6 22.5HarderianGland RFMmice F Fissionneutrons 36+10 2.5 14.6AllEpithelial B6CF1mice M Fissionneutrons 28.3+4.0 2.3+0.3 12.1+4.5Lung B6CF1mice M Fissionneutrons 24.3+4.6 2.2+0.3 11.0+2Liver B6CF1mice M Fissionneutrons 39.1+12.1 2.0+0.3 19.3+5.6GlandularandReproductiveOrgans
B6CF1mice M Fissionneutrons 49.3+7.8 4.3+0.3 16.6+5.6
HarderianGland B6CF1mice M Fissionneutrons 50.7+10.8 4.7+0.3 12.1+2.9AllEpithelial B6CF1mice F Fissionneutrons 21.9+3.3 1.7+0.3 11.0+1.6Lung B6CF1mice F Fissionneutrons 18.1+4.2 1.8+0.3 10.3+2.2Liver B6CF1mice F Fissionneutrons 23.3+11.6 5.9+0.3 4.4+1.6GlandularReproduct B6CF1mice F Fissionneutrons 84.4+20.8 12.2+0.3 7.4+1
HarderianGland B6CF1mice F Fissionneutrons 61.9+31.5 8.7+0.3 5.8+1.2
Estimates of, RBEmax, the tumor specific DDREF, and RBEγAcute for low dose HZE particles or neutrons relative to acute γ-rays.
DataofFryetal.,Alpenetal..Weiletal.,Grahnetal.(24week)andUllrichetal.74
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Reducing Uncertainty in QFmax parameter
RBEmax or RBEγAcute
1 10 100
%C
DF
0
20
40
60
80
100
RBEγAcute
RBEmax
Fit RBEγAcute
Fit RBEmax
CucinottaPLoSOne(2015)75Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Revised NASA Quality Factor- 2015based on mouse solid tumor RBE data for neutrons and HZE particles against low dose-rate or acute gamma-rays
Cucinotta PloS One (2015)
RBEorQFforFissionneutronsareaveragedoverlowenergyproton,HIrecoilsetc.Spectra
ResultssuggestFissionneutronsandHZEIronhavesimilarRBEsandnotmaxeffectiveradiations 76
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Centra
l Esti
mate
One S
igma
Upper
90% C
I
Upper
95% C
I
Saf
e D
ays
in S
pace
0
200
400
600
800
1000
NSCR-2014 FemalesNSCR-2012 FemalesNSCR-2014 MalesNSCR-2012 Males
Revised NSCR adds ~120 Safe Days in SpaceRisk and Uncertainties reduced ~30% in this new approach
77Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Cucinotta et al., Life Sci Space Res (2015)Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
79
Predictionsofpercentageriskofexposureinduceddeath(%REID)for1-yearspacemissionsatdeepsolarminimum.
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Major Unanswered Questions in Cancer Risk Estimates
1) ThereisalackofAnimalDataforHeavyionqualityfactorsformajortissuesinhumans(lung,breast,stomach,etc.).WillNASAeverfundsuchstudies?
2) ArethetumorsproducedbyHeavyionsandNeutronsmoremalignantthanthatofGamma-rays?
3) DoInverseDose-RateEffectsOccurforHighLETradiation?
4) DoNon-TargetedEffects(NTE)dominatedose-responsesatspacerelevantdoses?
80Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
1) Lack of Data for Human Tissues
• ExpertsagreethatMicearereasonablemodeltoestimateQualityFactorsandDose-Ratemodifiers.
• However,humandatasuggestsLung,Stomach,Breast,Colon,Bladderetc.dominatehumanradiationrisk.
• Mouseexperimentsshowwidevariationinradiationqualityeffectsfordifferenttumorsforgamma-raysandneutrons.
• NASAhasonlyfundeda1970’smodelofHarderianGlandtumorswith3ormoreparticlebeams.
• H.GlanddoesnotoccurinHumans.• Onlylimiteddataavailableforrelevanttumortypes!
• 21stCenturyMousemodelshavenotbeenfundedforriskestimates,onlylimitedmechanisticstudies.
• MajorimplicationsleadingtolargeuncertaintieswhichreflectsvariabilityinAvailabledataratherthanBestData.
81Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
2) Qualitative Differences in Cancer Risks from GCR
• RiskModelsonlyaccountforquantitativedifferencesusingQualityFactors(QFs)orPDFs
• IssuesemergingfromresearchstudiesofGCRSolidcancerrisks
• Earlierappearanceandaggressivetumorsnotseenwithcontrols,gamma-raysorprotoninducedtumors
• Non-linearresponseatlowdoseduetoNon-TargetedEffectsconfoundsconventionalparadigmsandRBEestimates
• SPE(proton)tumorsaresimilartobackgroundtumors
82Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
GCR Heavy ions produce more aggressive tumors compared to background or X-ray tumors
83
UTMB NSCOR- PI Robert Ullrich Shows much higher occurrence of metastatic Liver (HCC) tumors from GCR Fe or Si nuclei compared to gamma-rays or protons
Georgetown NSCOR- PI Al Fornace Shows much higher occurrence of invasive carcinomas tumors from GCR Fe nuclei compared to gamma-rays or protons
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
3) Inverse Dose-Rate Effects?
• StudieswithfissionneutronsdemonstratedanInversedose-rateeffectforsolidtumorsinmicewherechronicexposuresweremoreeffectivethanacuteexposures.
• Reportsofinversedose-rateeffectsvariedwithtissuetype,dose,sex,etc.
• Cellsterilizationeffectsareconfounder.• Notobservedwithgamma-raysorXrays.
• Short-termstudieswithHZEparticleshaveonlyconsidereddosefractionationanddonotsuggestaninverse-doserateeffectoccurs.
• Long-termchronicHZEparticleirradiationsimilartooldfissionneutronstudieshavenotbeenconducted
• NSCR-2015utilizesGrahnetal.24weekFissionneutrondata.Thereforeinversedose-rateeffectsshouldbereflectedinRBEvaluesconsidered,howeverlackingunderlyingunderstandingoftheeffect. 84
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
4) Non-Targeted Effects and GCR
• Non-targetedeffects(NTE)includegenomicinstabilityintheprogenyofirradiatedcellsandvariousbystandereffects
• NTEchallengeslinearmodelusedatNASAisapotentialgame-changeronroleofMissionlength,shieldingandbiologicalcountermeasures
• Non-linearor“flat”doseresponsesissuggestedformanynon-targetedeffectsatlowdose
• Epithelial-mesenchymaltransition(EMT)• Chromosomalaberrationsandmicro-nuclei• Mousesolidtumors• Geneexpressionandsignaling
• UnderstandingNTE’siscriticalresearchareatoreducecancerriskuncertainty
TheLancetOncology(2006)
ConventionalvsNTEDoseResponse
85Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Broad Beam Heavy Ion Irradiation Leads to Non-Linear Response at low doses for Chromosome Aberrations in Human Fibroblasts but not Lymphocytes
Tracks per Cell Nucleus0.01 0.1 1 10
Sim
ple
Exc
hang
es p
er 1
00 c
ells
per
Tra
ck
0
5
10
15
20
25
Fe(600 MeV/u)O(55 MeV/u)
Tracks per Cell Nucleus
0.01 0.1 1 10
Sim
ple
Exc
hang
es p
er 1
00 c
ells
per
Tra
ck
0
20
40
60
80
Fe(300 MeV/u)Fe(450 MeV/u)
Conventional Model
Hada, George, Wang and Cucinotta, Radiat Res (2014)86
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
H. Gland Experiment Update
• E.BlakelyhascollecteddataonlowdoseirradiationofB6CF1micewithSi,Ti,andFeparticles.ThisispartlyacontinuationofexperimentfundedlargelybyDoEin1980sandearly1990s(FryandAlpen).
• MostcompletesetofHeavyiontumordata(p,He,Ne,Fe,Nb,La)
• UNLV(E.CacaoandF.Cucinotta)haveperformeddataanalysisofTEandNTEdoseresponsemodelsandRBEmaxandRBEγAcuteestimates.
• NewandoldGamma-raydataandFeparticledataarenotsignificantlydifferent;One-wayrepeatedNova:0.57and0.24,respectively.
• Oldexpt.usedpartialbodywithpituitaryisografts• Newexpt.wholebodywithdataonothertumorscollected
87Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
88
Parameter TE NTE1 NTE2P0 3.07+0.36(<10-4) 2.75+0.34(<10-4) 2.77+0.36(<10-4)α0,Gy-1 7.65+3.94(<0.058) 10.05+3.56(<0.007) 1.21+4.5(<0.789)α1,Gy-1(keV/µm)-1 1.25+0.14(<10-4) 0.90+0.21(<10-4) 1.07+0.14(<10-4)α2,(keV/µm)-1 0.0038+0.0004(<10-4) 0.0039+0.0009(<10-4) 0.0036+0.0003(<10-4)β,Gy-2 6.02+3.51(<0.093) 4.61+3.33(<0.173) 9.24+3.46(<0.01)λ0,Gy-1 0.243+0.07(<0.001) 0.219+0.078(<0.007) 0.286+0.0533(<10-4)λ1,Gy-1(keV/µm)-1 0.006+0.0036(<0.097) 0.0047+0.0059(<0.424) 0.0042+0.0037(<0.258)λ2,(keV/µm)-1 0.0043+0.0027
(<0.124)0.0051+0.0059(<0.391) 0.0045+0.0041(<0.277)
κ1,(keV/µm)-1 - 0.048+0.023(<0.038) 3.14+1.13(<0.008)κ2,(keV/µm)-1 - 0.0028+0.0019(<0.141) -
StatisticalTestsAdjustedR2 0.9248 0.9373 0.9337AIC 269.6 260.8 263.3BIC 285.9 281.3 281.7
Table 6. Parameter estimates for combined data sets for TE and NTE models for the dose response for percentage tumor prevalence. For each statistical test considered, which adjust for the differences in the number of model parameters, the model providing the optimal fit is shown in bold-face.
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
H. Tumor Fluence Response
89
NTE1model
%prevalence
0
22.5
45
67.5
90
trackspercellnuclei0.0001 0.001 0.01 0.1 1 10 100 1000 10000
H(expt)H(NTE1model)He(expt)He(NTE1model)Ne(expt)Ne(NTE1model)Si(expt)Si(NTE1model)Ti(expt)Ti(NTE1model)Fe(newexpt)Fe(oldexpt)Fe193(NTE1model)Fe253(expt)Fe253(NTE1model)Nb(expt)Nb(NTE1model)La(expt)La(NTE1model)gamma(old+newexpt)gamma(model)
alpha=f(LET)kappa=f(LET)lambda=f(LET)
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
H. Gland RBE Estimates in UNLV Combined Old and New Data Models (Chang et al. (2015))
90
Z LET,keV/µm RBEmax RBEγAcute RBE(NTE1)at0.1Gy
RBE(NTE1)at0.01Gy
1 0.4 1.78+0.92 0.90+0.44 0.92 1.112 1.6 2.10+0.98 1.06+0.46 1.14 1.90
10 25 7.86+2.07 3.96+0.81 5.19 16.26
14 70 16.28+3.81 8.21+1.34 11.25 38.56
22 107 21.07+4.86 10.63+1.69 14.81 52.46
26 175 26.18+6.13 13.20+2.16 18.86 69.75
26 193 26.91+6.36 13.57+2.26 19.50 72.87
26 253 28.01+6.87 14.13+2.53 20.70 79.84
41 464 23.34+6.89 11.77+2.86 18.45 78.53
57 953 8.61+3.92 4.34+1.84 7.83 39.21
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Conclusions
• RevisedModelestimatessignificantlyreduceREIDpredictionsanduncertaintybands.
• Howeverlargequestionsremain:• Toomanyexperimentsatnon-relevantdoses(>0.2Gy)• ScarcityofHZEparticletumordata?• Inverse-doserateeffectsforchronicirradiation?• HigherlethalityofHZEparticletumors?• Non-targetedeffectsalteringshapeofdoseresponseandincreasingRBEestimates?
• Non-cancerriskscontributionstoREID?• Doeschronicinflammationoccuratlowdose?• Under-developedapproachestousetransgenicanimalsandothernewexperimentalmodelstoestimatehumanspaceradiationrisks?
91Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Other material
92Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
93
Dose Response Models: Linear vs NTE?
• Non-TargetedEffect(NTE)paradigm’shaveemergedfordescribinglowdoseeffects,includingthresholdsandnon-lineardoseresponses
• ForHeavyChargedParticlesmostexperimentsperformedatlessthanonetrack/cellshowthatthebestrepresentativemodelisastep-function(Θ) plusalineardoseresponse:
R=R0+κΘ(Dth) +α Dose
• LowDoseexpts.showthatexpts.atmoderateorhighdosefindingalineardoseresponseshouldbechallengedandlikelynotusefulforNASA
• RBEsintheNTEmodelwillexceedlinearextrapolationbyalargeamount:
RBENTE=RBETE(1+Dcross/Dose);Dcrossisdose
whereTE=NTE
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Components to Solution of Space Radiation Problem
94
Radiation Shielding Materials, Optimization, and
neutron minimization
▪ The current risk for a Mars mission is nearly 3-fold above acceptable risk levels ▪ Baseline DRM for a 1000 day mission has >3-fold uncertainties, assumes aluminum shielding, and radiation sensitivity of the U.S. average population
Dosimetry and Forecasting Ensure minimal SPE threat
Crew Selection Never-smokers, Screening for
sensitivity to GCR
Biological Mitigator’s New approaches to chronic, high
LET exposure protection
<1-fold (+100%)
15 %
50 %
30 %
Solar max. safety
Science understanding, radiobiology data-base for cancer, CNS, and other risks
Testing and validation
Biomarker developments, science discovery and verification, largely based on uncertainty reduction research
Drug testing and discovery, and validation based on uncertainty reduction research
Testing and validation
Uncertainty reduction Radiation quality effects, chronic
exposure, etc.
Solution Component Reduction Required Need
+σ
+σ
+σ
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
CNS Injury After High and Low Doses
• Higher Doses: • Generally restricted to white matter; • A late effect, appearing after a latent period; • Imaging and clinical changes; • Histology: demyelination, vascular damage, necrosis.
• Low Doses: Neurocognitive effects occur after radiation doses that do not result in overt tissue destruction:
• Progressive, currently untreatable and poorly understood;
• Hippocampal functions of learning, memory and spatial information processing;
• Other poorly understood - Unknown pathogenesis.
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Low priorities - Space Physics and Acute Radiation Syndrome Research
96Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
2013 National Academy of Sciences Review of NSCR-2010 Model
“TheCommitteeconsidersthattheradiationenvironmentandshieldingtransportmodelsusedintheNASA’sproposedmodelareamajorstepforwardcomparedtopreviousmodelsused.Thisisespeciallythecaseforthestatisticalsolarparticleeventmodel.Thecurrentmodelshavebeendevelopedbymakingextensiveuseoftheavailabledataandrigorousmathematicalanalysis.Theuncertaintiesconservativelyallocatedtothespacephysicsparametersaredeemedtobeadequateatthistime,consideringthatthespacephysicsuncertaintiesareonlyaminorcontributortotheoverallcancerriskassessment.Althoughfurtherresearchinthisareacouldreducetheuncertainty,thelawofdiminishingreturnsmayprevail.”
97Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Human Research Program – External Review (2010)
98
Cancer11:Whatarethemosteffectiveshieldingapproachestomitigatecancerrisks?The2012HRPExternalStandingReviewPanel(SRP)concluded:“ThisisnotproperlyagapintheHRPIRPbutanengineeringproblem.TheHRPIRPprovidesthescientificbasisonwhichshieldingevaluationscanbebased,butadditionalexperimentstodevelopshieldingarenotneeded.Inthefuture,acarefullydefinedmeasurementofarestrictedsetofcriticalparametersmaybeusefultovalidatesuchcalculations.TheSRPidentifiedthistaskasbeingoflowerpriorityandusingresourcesthatwouldbebetterappliedtothebiologicalinvestigations.”Cancer12:WhatlevelofaccuracydoNASA’sspaceenvironment,transportcodeandcrosssectionsdescriberadiationenvironmentsinspace(ISS,Lunar,orMars)?”ThePanelbelievesthat,atthistime,theaccuracyofpredictingparticlefluxesinspace(oftheorderof±15%)issufficientforriskpredictionandcouldnotbesignificantlyimprovedwithoutamajorinvestmentinresourcesbetterutilizedinaddressingothergaps.”
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
HRP External Review (2010)Cancer13:Whatarethemosteffectiveapproachestointegrateradiationshieldinganalysiscodeswithcollaborativeengineeringdesignenvironmentsusedbyspacecraftandplanetaryhabitatdesignefforts?SRP:“Thisisatechnologytransferproblemandnotaresearchproblem.Itshouldbeaddressedbytheappropriateengineeringprogramsandtheresourcesdevotedtoitwouldbebetterutilizedbyexpandingsupportofthehigherprioritygaps.”Acute–5:WhataretheoptimalSPEalertanddosimetrytechnologiesforEVAs?SRP:“Thisisatechnologyissue/engineeringproblem.Ifthisgapremains,theSRPrecommendsassigningitalowerpriority.Acute–6:Whatarethemosteffectiveshieldingapproachestomitigateacuteradiationrisks,howdoweknow,andimplement?SRP:“Thisisatechnologytransferproblemandnotaresearchproblem.Itshouldbeaddressedbytheappropriateengineeringprogramsandtheresourcesdevotedtoitwouldbebetterutilizedbyexpandingsupportofthehigherprioritygaps.”
99Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
GCR Environment Model
• LocalInter-stellarSpectra(LIS)(LeakyBoxModel)
• ModificationofCRISLeakyBoxmodel(Georgeetal.2009;Laveetal.,2013)
• ParkerTheoryofSolarModulation
])/()/(1[),(
2121
0αα
γ
EEEEEFEZFLIS ++
=− 2)15000/(
10 ]1[)( EeE −−+= γγγ
100Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Ironχ2/n=4.9
E, MeV/u101 102 103 104 105
φ (E)
, 1/(M
eV/u
cm
2 sr s
)
10-12
10-11
10-10
10-9
10-8
10-7
Φ=0 MVΦ=200 MVΦ=300 MVΦ=500 MVΦ=850 MVCRIS (2009-10)CRIS (1996-97))CRIS (2001-03)HEAO3(1980)TRACER (2003)U. Chicago(1975)U. Minnesota (1977)UNH (1975)CREAM (2005)
Siliconχ2/n=4.3
E, MeV/u101 102 103 104 105
φ (E
), 1/
(MeV
/u c
m2 s
r s)
10-12
10-11
10-10
10-9
10-8
10-7
10-6
Φ=0 MV (LIS)Φ=250 MVΦ=350 MVΦ=550 MVΦ=900 MVCRIS (2009-10)CRIS (1996-97)CRIS (2002-03)HEAO-3 (1980)CREAM (2005)TRACER (2003)U. Minnesota (1977)UNH (1975)
Oxygenχ2/n=5.0
E, MeV/u101 102 103 104 105
φ (E)
, 1/(M
eV/u
cm
2 sr s
)
10-11
10-10
10-9
10-8
10-7
10-6
LISΦ=200 MVΦ=300 MVΦ=500 MVΦ=850 MVCRIS (2009-10)CRIS (1996-97)CRIS (2001-03)HEAO3 (1980)UNH(1975)TRACER (2003)
Titaniumχ2/n=6.6
E, MeV/u101 102 103 104 105
φ (E)
, 1/(M
eV/u
cm
2 sr s
)
10-13
10-12
10-11
10-10
10-9
10-8
10-7
LISΦ=200 MVΦ=300 MVΦ=500 MVΦ=850 MVCRIS (2009-10)CRIS (1996-97)CRIS (2001-03)HEAO3 (1980)U. Minnesota (1977)
101Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Modulation Parameter Uncertainty-Fits to CRIS Data
Year1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
PH
I(MV
)
0
200
400
600
800
1000Fit IronFit SiliconFit NeonFit Oxygen
Monthly Average Modulation
Year1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016
PH
I(MV
)
0
200
400
600
800
1000
1200
102Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
E,m
Sv
0
175
350
525
700
x,g/cm2
0 30 60 90 120
AnnualGCRatSolarMinimuminInterplanetarySpace
AnnualGCRatSolarMaximuminInterplanetarySpace
Aluminum
Polyethylene
AnnualExposureatLEO(51.6ox400km)atSolarMinimum
AnnualExposureatLEO(51.6ox400km)atSolarMaximum
AnnualEffectiveDoseforMales
103Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Space Physics Over-Statements
104
Originalclaim
Correction:
Mewaldtpaperanalyzeddifferentsolarminspectrawithdifferentmethodsleadingtoover-statementof2009spectra;errorcorrectedinLaveetal.;APJ2013
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
The Carrington event not observed in most ice core nitrate recordsE. Wolff, J. Geophy Lett (2012)
• TheCarringtonEventof1859isconsideredtobeamongthelargestspaceweathereventsofthelast150years.Weshowthatonlyoneoutof14well-resolvedicecorerecordsfromGreenlandandAntarcticahasanitratespikedatedto1859.NosharpspikesareobservedintheAntarcticcoresstudiedhere.InGreenlandnumerousspikesareobservedinthe40yearssurrounding1859,butwhereotherchemistrywasmeasured,alllargespikeshavetheunequivocalsignal,includingco-locatedspikesinammonium,formate,blackcarbonandvanillicacid,ofbiomassburningplumes.Itseemscertainthatmostspikesinanearliercore,includingthatclaimedfor1859,arealsoduetobiomassburningplumes,andnottosolarenergeticparticle(SEP)events.WeconcludethataneventaslargeastheCarringtonEventdidnotleaveanobservable,widespreadimprintinnitrateinpolarice.NitratespikescannotbeusedtoderivethestatisticsofSEPs.
105Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Solar protons a manageable issue with no significant acute risks
1.E+07
1.E+08
1.E+09
1.E+10
2/1/1954
2/1/1956
2/1/1958
2/1/1960
2/1/1962
2/1/1964
2/1/1966
2/1/1968
2/1/1970
2/1/1972
2/1/1974
2/1/1976
2/1/1978
2/1/1980
2/1/1982
2/1/1984
2/1/1986
2/1/1988
2/1/1990
2/1/1992
2/1/1994
2/1/1996
2/1/1998
2/1/2000
2/1/2002
2/1/2004
2/1/2006
Date
Φ60
, pro
tons
cm
-2
1.E+07
1.E+08
1.E+09
1.E+10
2/1/1954
2/1/1957
2/1/1960
2/1/1963
2/1/1966
2/1/1969
2/1/1972
2/1/1975
2/1/1978
2/1/1981
2/1/1984
2/1/1987
2/1/1990
2/1/1993
2/1/1996
2/1/1999
2/1/2002
2/1/2005
Date
Φ10
0, p
roto
ns c
m-2
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
2/1/1954
2/1/1957
2/1/1960
2/1/1963
2/1/1966
2/1/1969
2/1/1972
2/1/1975
2/1/1978
2/1/1981
2/1/1984
2/1/1987
2/1/1990
2/1/1993
2/1/1996
2/1/1999
2/1/2002
2/1/2005
Date
Φ30
, pro
tons
cm
-2
SPE onset date
Flux>30MeV
Flux>60MeV
Flux>100MeV
Kim,Feivesen,Cucinotta,2009106
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Occurrence Of Extreme Solar Particle Events: Assessment From Historical Proxy DataUsoskin and Kovalstov, Astrophy J (2012)
107
100YearFluence
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
PredictingBFODosefromΦ30MeV(M.Y.Kimetal.)EquipmentRoom(5g/cm2Alum)inInterplanetarySpace
ToleranceLimitsbasedonVariabilityofDetailedEnergySpectra
SizeofSPE(>Φ30),protonscm-2
BFOdose,cGy
-Eq
10-2
102
101
100
10-1
103
1011108107 109 1010
Regressionfitwith90%tolerancelimits
■34historicallylargeSPEsoutof>400since1950
NASA30-dlimitatBFO
108
BFOdose,cGy
-Eq
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
SPE Blood forming organ doses with No shelter (Probability- D
BFO> 100 mGy per EVA) <1 x 10
-6
1) Dose-ratesaremodest(eventslast>10h)2) EVAterminationtime<2h3) ARSeasilymitigatedwithreal-timedosimetryandshielding
because>100MeVfluxistoosmall4) Spacecrafthaveareaswithatleast20g/cm2shielding5) ProbabilitytobeonanEVAduringanSPE<1x10-6 109
Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Storm shelters with ~40 g/cm2 shielding are practical
M.Y.Kim 110Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Lung Cancer Risk
• Lungcancercomprisesthelargestfractionofhumanradiationfatalrisk(>30%).
• YaWangetal.haveusedaresistantmousemodel(C57BL/6)toreportonfirstHeavyionlungtumordata.
• ResultsshowlittleeffectofdosefractionationforO,Si,andFeparticlesat1Gy.
• Siparticlesproducemoreaggressivelungtumorscomparedtogamma-rays.
• Follow-upstudiesplannedatlowerdoses.
111Wangetal.RadiatRes(2014)Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Argonne National Lab Inverse Dose-Rate Effect- D. Grahn et al, 1993
(24 or 60 week x 5 d/wk gamma or fission neutron)
112Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Lung tumors: Inverse Dose-Rate Effect Found?
113Francis Cucinotta, “New Estimates of Radiation Risks…” NASA FISO, July 13, 2016
Space Radiation ENAE 697 - Space Human Factors and Life Support
U N I V E R S I T Y O FMARYLAND
References• Francis Cucinotta, “New Estimates of Radiation Risks”
NASA Future In-Space Operations Working Group, May 18, 2011
• –, Human Integration Design Handbook, NASA SP-2010-3407, Jan. 2010
• Lora Bailey, “Radiation Studies for a Long Duration Deep Space Habitat” NASA Future In-Space Operations Working Group, Oct 31, 2012
• Francis A. Cucinotta, Myung-Hee Y. Kim, and Lei Ren, Managing Lunar and Mars Mission Radiation Risks Part I: Cancer Risks, Uncertainties, and Shielding Effectiveness NASA/TP-2005-213164, July, 2005
114
National Aeronautics and Space Administration
Mars Mission and Space Radiation Risks
Overview
Briefing to
NAC HEOMD/SMD Joint Committee
April 7, 2015
Steve Davison • HEOMD • NASA Headquarters
Space Radiation Presentations
Overview
• Mars Mission and Space Radiation Risks Steve Davison, NASA-HQ, 30 min
Health Standards Decision Framework David Liskowsky, NASA-HQ, 10 min•
Space Radiation Environment
• Introduction Chris St. Cyr, NASA-GSFC, 5 min
Solar Energetic Particles Allan Tylka, NASA-GSFC, 30 min
Comparison and Validation of GCR Models Tony Slaba, NASA-LaRC, 30 min
GCR Radiation Environment Predictions Nathan Schwadron, Univ. of NH, 30 min
Emerging GCR Data from AMS-2 Veronica Bindi, Univ. of Hawaii, 30 min
•
•
•
•
Radiation Health Risk Projections Eddie Semones, NASA-JSC, 45 min
• NCRP Recommendations, Permissible Exposure Limits, Space Radiation Cancer Risk Model,
Operations and In-Flight Solar Particle Event Mitigations
Space Radiation R&T for Risk Mitigation Lisa Simonsen, NASA-LaRC, 45 min
• Radiobiology Research Portfolio (Cancer, CNS, Cardio) and Spacecraft Shielding Design,
Analysis, and Optimization
2
Overview of Mars Mission Crew Health Risks
• Mission And Crew Health Risks Are Associated With Any Human Space Mission
– Briefing is focused on space exploration crew health risks associated with space
radiation
• Exploration Health Risks Have Been Identified, And Medical Standards Are In
Place To Protect Crew Health And Safety
– Further investigation and development is required for some areas, but this work
will likely be completed well before a Mars mission launches
• There Are No Crew Health Risks At This Time That Are Considered “mission-
stoppers” for a Human Mission to Mars
– The Agency will accept some level of crew health risk for a Mars mission, but that
risk will continue to be reduced through research and testing
• The Most Challenging Medical Standard To Meet For A Mars Mission Is That
Associated With The Risk Of Radiation-induced Cancer
– Research and technology development as part of NASA’s integrated radiation
protection portfolio will help to minimize this long-term crew health risk3
Human Spaceflight Risks are Driven by
Spaceflight Hazards
Distance from Earth
Drives the need for additional “autonomous” medical care
capacity – cannot come home for treatment
Hostile/
Closed Environment
Vehicle DesignEnvironmental – CO2 Levels, Toxic Exposures, Water, Food
Isolation & Confinement
Behavioral aspect of isolationSleep disorders
Space Radiation
Acute In-flight effectsLong-term cancer risk
CNS and Cardiovascular
Altered Gravity -Physiological Changes
Balance DisordersFluid Shifts
Visual AlterationsCardiovascular DeconditioningDecreased Immune Function
Muscle AtrophyBone Loss
4
Human System Risk Board (HSRB):
Human Risks of Spaceflight Summary
Altered Gravity Field1. Spaceflight-Induced Intracranial
Hypertension/Vision Alterations2. Renal Stone Formation 3. Impaired Control of
Spacecraft/Associated Systems and Decreased Mobility Due to Vestibular/Sensorimotor Alterations Associated with Space Flight
4. Bone Fracture due to spaceflight Induced changes to bone
5. Impaired Performance Due to Reduced Muscle Mass, Strength & Endurance
6. Reduced Physical Performance Capabilities Due to Reduced Aerobic Capacity
7. Adverse Health Effects Due to Host-Microorganism Interactions
8. Urinary Retention9. Orthostatic Intolerance During Re-
Exposure to Gravity10.Cardiac Rhythm Problems11.Space Adaptation Back Pain
Radiation1. Risk of Space Radiation
Exposure on Human Health (cancer, acute, cardio, CNS)
Distance from Earth1. Adverse Health Outcomes
& Decrements in Performance due to inflight Medical Conditions
2. Ineffective or Toxic Medications due to Long Term Storage
—
Isolation1. Adverse Cognitive or
Behavioral Conditions & Psychiatric Disorders
2. Performance & Behavioral health Decrements Due to Inadequate Cooperation, Coordination, Communication, & Psychosocial Adaptation within a Team
Each risk will be controlled by a NASA standard to protect crew health and safety—
Hostile/Closed Environment-Spacecraft Design1. Acute & Chronic Carbon Dioxide
Exposure2. Performance decrement and crew illness
due to inadequate food and nutrition3. Reduced Crew Performance Due to
Inadequate Human-System Interaction Design (HSID)
4. Injury from Dynamic Loads5. Injury and Compromised Performance
due to EVA Operations6. Adverse Health & Performance Effects of
Celestial Dust Exposure7. Adverse Health Event Due to Altered
Immune Response8. Reduced Crew Performance Due to
Hypobaric Hypoxia9. Performance Decrements & Adverse
Health Outcomes Resulting from Sleep Loss, Circadian Desynchronization, & Work Overload
10.Decompression Sickness11.Toxic Exposure12.Hearing Loss Related to Spaceflight13.Injury from Sunlight Exposure14.Electrical shock/plasma
5
Mars Mission Human Health Risks
Based On The On-going Human System Risk Board (HSRB) Assessment, The Following Risks Are The Most Significant For A Mars Mission:
• Adverse affect on health space radiation exposure (long-term cancer risk)
spaceflight-induced vision alterationsrenal stone formation compromised health due to inadequate nutritionbone fracture due to spaceflight induced bone changesacute and chronic elevated carbon dioxide exposure
•
•
Post
Mission
Risks
Inability to provide in mission treatment/care lack of medical capabilitiesineffective medications due to long term storage
Adverse impact on performancedecrements in performance due to adverse behavioral conditions and training deficienciesimpaired performance due to reduced muscle and aerobic capacity, and sensorimotor adaptation
In-
Mission
Risks
6
Current Space Flight Health Standards
• NASA Should Be Able To Meet
All Fitness for Duty (FFD) And
Permissible Outcome Limits
(POL) Standards For A Mars
Mission
– Based on long-duration ISS
flight experience and
mitigation plans
• Meeting The Current Low Earth
Orbit (LEO) Space Radiation
Permissible Exposure Limit
(PEL) Standard Will Be
Challenging For A Mars
Mission
– NASA exposure limit is the
most conservative of all space
agencies
Area Type Standard
Bone POL Maintain bone mass at ≥-2SD
Cardiovascular FFD Maintain ≥75% of baseline VO2 max
Neurosensory FFD Control motion sickness, spatial disorientation, & sensorimotor deficits to allow operational tasks
Behavioral FFD Maintain nominal behaviors, cognitive test scores, adequate sleep
Immunology POL WBC > 5000/ul; CD4 + T > 2000/ul
Nutrition POL 90% of spaceflight-modified/USDA nutrient
requirements
Muscle FFD Maintain 80% of baseline muscle
strength
Radiation PEL ≤ 3% REID (Risk of Exposure Induced
Death, 95% C.I. 7
Space Radiation Challenge
Galactic cosmic rays (GCR) – penetrating protons and heavy nuclei
Solar Particle Events (SPE) – low to medium energy protons
What are the levels of
radiation in deep
space and how does
it change with time?
SMD R&D
Helio- & Astrophysics
Characterization/meas
urement
Modeling/Prediction &
Real-time Monitoring
How much radiation is inside the spacecraft, on Mars surface, and in the human body?
HEOMD R&D
Radiation Transport Code Development
Transport of radiation into body
Tissue/Organ doses
What are the health
risks associated
with radiation
exposure?
Cancer risks
Acute radiation
Non-cancer risks
How do we mitigate
these health risks?
NSRL research
Spacecraft Shielding
Bio-Countermeasures
Medical Standards
8
Space Radiation Health Risks
Health Risk Areas
CarcinogenesisSpace radiation exposure may cause
increased cancer morbidity or mortality risk in
astronauts
Status
Cancer risk model developed for mission risk
assessment
Model is being refined through research at
NASA Space Radiation Laboratory (NSRL)
Health standard established
Acute Radiation Syndromes from SPEsAcute (in-flight) radiation syndromes, which
may be clinically severe, may occur due to
occupational radiation exposure
Acute radiation health model has been
developed and is mature
Health standards established
Risk area is controlled with operational &
shielding mitigations
Degenerative Tissue EffectsRadiation exposure may result in effects to
cardiovascular system, as well as cataracts
Central Nervous System Risks (CNS)Acute and late radiation damage to the
central CNS may lead to changes in
cognition or neurological disorders
Non-cancer risks (Cardiovascular and CNS)
are currently being defined
Research is underway at NSRL and on ISS
to address these areas
Appropriate animal models needed to assess
clinical significance
9
Mars Mission Space Radiation Risks
Mars Missions May Expose Crews To Levels Of Radiation Beyond Those
Permitted By The Current LEO Cancer Risk Limit (≤ 3% REID, 95% C.I.)
• May increase the probability that a crewmember develops a cancer over their
lifetime and may also have undefined health effects to central nervous system
and/or cardiovascular system; these areas are currently under study
Mars Missions Cancer Risk Calculations
• Calculations use 900-Day conjunction class (long-stay) trajectory option for Mars
mission (500 days on Mars surface)
– Exposure levels are about the same for 600-Day opposition-class (short-stay)
trajectory option (30 days on Mars surface)
• Based on 2012 NASA Space Radiation Cancer Risk Model as recommended by
the National Council on Radiation Protection and reviewed by National Academies
– Model calculates risk of exposure induced death (REID) from space
radiation-induced cancer with significant uncertainties
Calculations take into range of solar conditions and shielding configuration
Mars surface calculations include shielding by the planet, atmosphere, &
lander
–
–
10
Post Mission Cancer Risk For A 900-day Mars Mission
Mars Mission Timing
Mission Shielding Configuration Calculated REID, 95% C.I. (Age=45, Male-Female)
Amount Above3% Standard
Solar Max Good shielding like ISS (20 g/cm2)w/no exposure from SPEs
4% - 6% 1% - 3%
Solar Max Good shielding like ISS (20 g/cm2) w/large SPE
5% - 7% 2% - 4%
Solar Min Good shielding like ISS (20 g/cm2) 7% - 10% 4% - 7%
NASA Standards Limit The Additional Risk Of Cancer Death By Radiation
Exposure, Not The Total Lifetime Risk Of Dying From Cancer
• Baseline lifetime risk of death from cancer (non-smokers)
– 16% males, 12% females
• After Mars Mission (solar max), Astronauts lifetime risk of death from cancer ~20%
Mars Space Radiation Risk For Solar Max Can Be Explained As Follows
• If 100 astronauts were exposed to the Mars mission space radiation, in a worst case (95%
confidence) 5 to 7 would die of cancer, later in life, attributable to their radiation exposure and
their life expectancy would be reduced by an average on the order of 15 years
Challenging to use a population-based risk model to estimate individual risk for the few
individuals that would undertake a Mars Mission 11
•
Radiation Protection Portfolio
Optimize human radiation protection by integrating research,
operations and development activities across the agency
Integrated Radiation Protection
Radiation Exposure Standard
OCHMO
Space Radiation Environment
SMD, Monitoring/Prediction Advances
External Advisory Panels
NCRP, NAS, SRP, NAC
Monitoring Devices
In flight Crew MonitoringDosimeter Technology Development
Shielding/Vehicle Design
Models to enable exposure assessment Shielding Optimization
Occupational Surveillance
Pre- and In- Mission CarePost Mission Screening/Treatment
Countermeasures
Advances in Nutrition/Pharmaceuticals
Analysis, Operations, Mission Planning
Radiation Assessment ModelsAssessment & Planning, SRAG
Space Radiation Biological Effects
Radiobiology research on cancer, CNS, and cardiovascular
12
Reducing Mars Mission Radiation Risks
NASA Is Working Across All Phases Of The Mars Mission To Minimize The Space Radiation Health Risk
Pre - Mission
Radiation FactorsIndividual Sensitivity –
Biomarkers*
Selection – age, gender
Model Projection of Risk
Space Radiation Envir. Model
In - Mission
Radiation FactorsShielding
Mission Duration
Solar Min vs. Max
Operational Planning
Dosimetry
Countermeasures*
- Pharmaceutical &
Nutritional
Post - Mission
Radiation FactorsOccupational Health Care
for Astronauts*
- Personalized Cancer
Screening, Biomarkers
- Cancer Treatment
Reduction in Total Risk Posture
*long-term
development
13
Reducing Radiation Health Risks
Space Radiation Research at NSRL
• Key to reducing the space radiation health effects uncertainties, refinement of cancer risk model, and understanding cardiovascular and CNS risks
•
•
•
•
•
•
LRO-CRaTER
radiation
measurements
Space Radiation Environment Characterization
LRO-CRaTER measurements of radiation environment
SEP real-time monitoring and characterization
MSL-RAD Measurements of radiation environment during transit and on the surface of Mars
Medical Approaches Applied Pre-/Post-Mission
Understanding the individual sensitivities and enhancing post mission care are the key areas that can significantly reduce the space radiation risk
MSL-RAD
radiation
measurements
on Mars
Exploration Space Radiation Storm Shelter Design and Real-time Radiation Alert System
Development of these capabilities for exploration missions can reduce crew exposure risk to SPEs to negligible levels
Mars Mission Design and Deep Space Propulsion
Reducing deep space transit times can reduce space radiation exposure and mitigate human health risks
NSRL simulates space cosmic
and solar radiation environment
14
Summary
Based on current mitigation plans for Crew Health and Performance Risks, NASA can support a Mars Mission
• Mars Mission Health Risks Have Been Identified And Medical Standards Are In Place To Protect Crew Health And Safety
– While there is a fair amount of forward work to do, there are no crew health risks at this time that can be considered “mission-stoppers”
There will be a level of crew health risk that will need to be accepted by the Agency to undertake a Mars mission, but that risk will continue to be reduced through R&D
–
• Based on present understanding of risks and standards
– Exercise countermeasure approaches (hardware & prescriptions) require further refinement/optimization to meet exploration mission, vehicle, and habitat designs
Additional data needed to fully quantify some risks (vision impairment, CO2 exposure)
Renal stone risk needs new intervention/treatment approaches
Some risks (nutrition, inflight medical conditions) require optimization in order to support a Mars Mission
Pharmaceutical & food stability/shelf life needs to be improved for a Mars Mission
Behavioral health and human factors impacts need to be further minimized
–
–
–
–
–
– The radiation standard would not currently be met 15