Radiation challenges for human exploration

Marco DuranteMarco Durante

Fourth European Space Weather Week, Bruxelles, Belgium, November the 9th, 2007

The goal of space radiation biophysics research:

To allow exploration and colonization with ACCEPTABLE risk from radiation

exposure

Astronauts go in EVA because they understand the risk!

Is cosmic radiation a showstopper for the colonization

of the Solar system?

Harmful Radiation Effects• Cancer• Tissue degenerative effects

(CNS, cardiovascular diseases, cataracts,…..)

• Acute radiation sickness• Hereditary effects

Health risks in space exploration

SPACERADIATION

HUMAN FACTORS

MICROGRAVITY

Behavioral Problems • Disorientation• Sleep problems • Psychosocial problemsAcute Medical Problems • Toxicity • Ambulatory health problems

Physiological Changes• Cardiac arrhythmia • Osteoporosis• Fluid redistribution (puffy face, shrinked legs….)• Loss of blood plasma, anemia• Muscle loss• Kidney stones

Concordia Mars-500

Two major radiation Two major radiation risks in exploratory risks in exploratory

missionsmissions

SPESPE: sporadic, : sporadic, high dose. high dose. Shielding generally Shielding generally effective. Acute effective. Acute (deterministic) (deterministic) effectseffects

GCRGCR: chronic, low : chronic, low dose. Shielding dose. Shielding poorly effective. poorly effective. Late (stochastic) Late (stochastic) effectseffects

Annual dose on Earth

Daily dose in LEO

CT abdomen/pelvis

Annual dose limit for radiation workers

AzoospermiaLymphopeniaNauseaVomiting

Haematopoietic syndrome

Chest X-ray film

GI syndrome

CNS syndrome

Pelvis X-ray film

Fibrosis

Skin desquamation

Annual dose in Kerala (India)

Annual cosmic rays at sea level

1

10

100

1000

10000

0.1

100000

Radiation doses in different missions

0.1

1

10

100

1000

104

1950 1960 1970 1980 1990 2000 2010 2020 2030

Dos

e (m

Sv)

Year

Gemini

Apollo

Skylab STS/Mir

Shuttle

ISS

Mars

Populationper year

RadWorkper year

Astronautscareer

Past Future

Radiation field on MarsRadiation field on Mars

About 100x Earth’s background

Relative contribution of different Relative contribution of different components of space radiation to components of space radiation to

dose equivalentdose equivalent

Solar particle events

Modelling SPEModelling SPE Worst case scenarios (NASA: Worst case scenarios (NASA:

4xOct89, ESA TT: MaxSEP) 4xOct89, ESA TT: MaxSEP) are generally considerd to be are generally considerd to be potentially lethalpotentially lethal

These events are very seldomThese events are very seldom

For assessement of health risk, it is necessary to take into account

Significant sparing effect Significant sparing effect (usually (usually dD/dtdD/dt<10 cSv/h)<10 cSv/h)

Contamination by HZE (high Contamination by HZE (high RBE) particlesRBE) particles

Secondary radiation produced Secondary radiation produced by shielding in high knee-by shielding in high knee-energy eventsenergy events

Stochastic risk can be higher Stochastic risk can be higher than nonstochasticthan nonstochastic

ESA TT on shielding, final report, ESTEC SP-1281, June 2005

Deterministic effectsDeterministic effects

Traditionally Traditionally identified as identified as nonstochastic nonstochastic early effects with early effects with thresholdthreshold

Actually, they Actually, they can be both early can be both early and late, and are and late, and are probabilisticprobabilistic

Risk is dose-rate Risk is dose-rate dependentdependent

0

0,2

0,4

0,6

0,8

1

0 5 10 15 20

Ris

k

Dose (Gy)

GI syndrome

Fibrosis

Vomiting

ESA TT on shielding, final report, ESTEC SP-1281, June 2005

Shielding of SPE – dose equivalent Shielding of SPE – dose equivalent for WCS 4xOct1989 eventfor WCS 4xOct1989 event

SPE and late stochastic riskSPE and late stochastic risk

Galactic cosmic radiation

                                                                    

GCR shielding (HZETRN calculation)

Aluminum ~ 30%

Polyethylene ~ 50%

Liquid hydrogen ~ 90%

Max GCR dose

reduction

                                                                    

Shielding on ISS

Sleep station outfitted with PE and waterThin, flat panels are PE shieldsStowage water packaging above the sleep station

                                                                    

Space radiation biology

Role of Uncertainties in Risk ProjectionsRole of Uncertainties in Risk Projections

1%

0.1%

.01%

Maximum Acceptable Risk

Shuttle Mission

ISS Mission

Mars Mission

Individual’s Fatal Risk

▲

▲

▲

“Point Estimate”

“95% Confidence Interval”

10%

Lunar▲

SPE??

DNA dsb visualized by immunofluorescence of -H2AX histone in human skin firbroblasts exposed to 2 Gy of ionizing radiation

-rays

silicon

ironCucinotta and Durante, Lancet Oncol. 2006

“Special” chromosomal damage induced by low doses of heavy ions

3 Gy -rays 0.3 Gy Fe-ions

Durante et al., Radiation Research 2002

Harderian gland tumors in mice

Data Alpen et al. (1993); IPP Model Cucinotta, et al. (1994)

Fluence, m2

10-3 10-2 10-1 100 101 102 103

Tum

or P

reva

lenc

e (%

)

0

20

40

60

80

100

Iron

Neon

-rays

Proton

Helium

AML incidence in CBA mice exposed to

Fe-ions or -raysControl # mice total (still alive) AML % total

0 cGy 157 (23) 0 0

Gamma cGy # mice total (still alive) AML % total

100 400 (65) 4 1.0

200 300 (50) 16 5.3

300 100 (1) 9 9.0

HZE cGy # mice total (still alive) AML % total

10 300 (0) 0 0

20 300 (0) 0 0

40 200 (0) 1 0.5

100 200 (0) 3 1.5

Radiation Leukemogenesis NSCOR Courtesy of M. Weil

Conclusions – SPEConclusions – SPE

Shielding will be very effective for any events Shielding will be very effective for any events with E<100-200 MeVwith E<100-200 MeV

For soft events, main risks are accelerated For soft events, main risks are accelerated cataractogenesis and skin erythema in EVAcataractogenesis and skin erythema in EVA

For hard spectra, prodromal syndrome is For hard spectra, prodromal syndrome is possible (around 2xFeb 1956 intensities)possible (around 2xFeb 1956 intensities)

SPE will increase stochastic risk, especially SPE will increase stochastic risk, especially leukemialeukemia

More research is needed in: RBE of H- and He-More research is needed in: RBE of H- and He-ions at low dose-rates, biomedical ions at low dose-rates, biomedical countermeasures for acute radiation sicknesscountermeasures for acute radiation sickness

Conclusions – GCRConclusions – GCR

Current uncertainties on biological effects Current uncertainties on biological effects are too high for long-term exploratory are too high for long-term exploratory missions, especially Marsmissions, especially Mars

Passive shielding can only partly solve the Passive shielding can only partly solve the problem, active shielding is not yet problem, active shielding is not yet availableavailable

More research is needed on biological More research is needed on biological effects of heavy ions: cancer risk, CNS effects of heavy ions: cancer risk, CNS damage, interaction with other space damage, interaction with other space environment stressors.environment stressors.