Transcript Biological effects of SPE for different fluences and

Radiation challenges for
human exploration
Marco Durante
Fourth European Space Weather Week, Bruxelles, Belgium,
November the 9th, 2007
Is cosmic radiation a showstopper for the colonization
of the Solar system?
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!
Health risks in space exploration
SPACE
RADIATION
Concordia
Mars-500
HUMAN
FACTORS
Harmful Radiation Effects
• Cancer
• Tissue degenerative effects
(CNS, cardiovascular
diseases, cataracts,…..)
• Acute radiation sickness
• Hereditary effects
Behavioral Problems
• Disorientation
• Sleep problems
• Psychosocial problems
Acute Medical Problems
• Toxicity
• Ambulatory health problems
MICROGRAVITY Physiological Changes
• Cardiac arrhythmia
• Osteoporosis
• Fluid redistribution (puffy
face, shrinked legs….)
• Loss of blood plasma, anemia
• Muscle loss
• Kidney stones
Two major radiation
risks in exploratory
missions
100000
CNS syndrome
Skin desquamation
GI syndrome
10000


SPE: sporadic,
high dose.
Shielding generally
effective. Acute
(deterministic)
effects
GCR: chronic, low
dose. Shielding
poorly effective.
Late (stochastic)
effects
Fibrosis
Haematopoietic syndrome
1000
100
10
Vomiting
Nausea
Lymphopenia
Azoospermia
Annual dose in Kerala (India)
Annual dose limit for
radiation workers
CT abdomen/pelvis
Annual dose on Earth
1
0.1
Daily dose in LEO
Pelvis X-ray film
Annual cosmic rays at sea leve
Chest X-ray film
Radiation doses in different
missions
10
Past
4
Future
Mars
Dose (mSv)
1000
Skylab
100
ISS
STS/Mir
RadWork
per year
Apollo
10
Astronauts
career
Shuttle
Population
per year
1
Gemini
0.1
1950
1960
1970
1980
1990
Year
2000
2010
2020
2030
Radiation field on Mars
About 100x Earth’s background
Relative contribution of different
components of space radiation to
dose equivalent
Solar particle events
Modelling SPE


Worst case scenarios (NASA:
4xOct89, ESA TT: MaxSEP)
are generally considerd to be
potentially lethal
These events are very seldom
For assessement of health risk, it
is necessary to take into
account



ESA TT on shielding, final report,
ESTEC SP-1281, June 2005

Significant sparing effect
(usually dD/dt<10 cSv/h)
Contamination by HZE (high
RBE) particles
Secondary radiation produced
by shielding in high kneeenergy events
Stochastic risk can be higher
than nonstochastic
Deterministic effects


Traditionally
identified as
nonstochastic
early effects with
threshold
Actually, they can
be both early and
late, and are
probabilistic
Risk is dose-rate
dependent
1
Vomiting
0,8
Risk

Fibrosis
0,6
GI syndrome
0,4
0,2
0
0
5
10
Dose (Gy)
ESA TT on shielding, final report,
ESTEC SP-1281, June 2005
15
20
Shielding of SPE – dose equivalent
for WCS 4xOct1989 event
SPE and late stochastic risk
Galactic cosmic radiation
GCR shielding (HZETRN calculation)
Aluminum ~ 30%
Max GCR dose
Polyethylene ~ 50%
reduction
Liquid hydrogen ~ 90%
Shielding on ISS
Sleep station outfitted with PE and water
Thin, flat panels are PE shields
Stowage water packaging above the sleep station
Space radiation biology
Role of Uncertainties in Risk Projections
10%
Maximum Acceptable Risk
▲
1%
0.1%
Mars
Mission
ISS Mission ▲
Lunar
▲
SPE??
“95% Confidence
Interval”
.01%
▲
Shuttle Mission
“Point Estimate”
Individual’s Fatal Risk
DNA dsb visualized by immunofluorescence of g-H2AX
histone in human skin firbroblasts exposed to 2 Gy of
ionizing radiation
g-rays
silicon
iron
Cucinotta and Durante, Lancet Oncol. 2006
“Special” chromosomal damage induced by low doses of heavy ions
3 Gy g -rays
Durante et al., Radiation Research 2002
0.3 Gy Fe-ions
Harderian gland tumors in mice
Tumor Prevalence (%)
100
Helium
80
Iron
Neon
60
Proton
40
g-rays
20
0
10-3
10-2
10-1
100
101
102
103
Fluence, m2
Data Alpen et al. (1993); IPP Model Cucinotta, et al. (1994)
AML incidence in CBA mice
exposed to
Fe-ions or g-rays
Control
# 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 – SPE

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Shielding will be very effective for any events
with E<100-200 MeV
For soft events, main risks are accelerated
cataractogenesis and skin erythema in EVA
For hard spectra, prodromal syndrome is
possible (around 2xFeb 1956 intensities)
SPE will increase stochastic risk, especially
leukemia
More research is needed in: RBE of H- and Heions at low dose-rates, biomedical
countermeasures for acute radiation sickness
Conclusions – GCR
Current uncertainties on biological effects
are too high for long-term exploratory
missions, especially Mars
 Passive shielding can only partly solve the
problem, active shielding is not yet
available
 More research is needed on biological
effects of heavy ions: cancer risk, CNS
damage, interaction with other space
environment stressors.
