space radiation and health risks

Human Space Physiology Training Course 2021 ESA Academy | Slide 1

Presented byPresented by

Space Radiation and Health Risks

ANNA FOGTMANSciSpacE and Space Medicine TeamEuropean Astronaut Centre European Space Agency


Towards space exploration

Before 2030:Science and Humans on the Moon’s orbit and surface.Assembly of deep space transport.

ISS Extension until 2030:More science on Low Earth Orbit.More long duration astronaut flights.

After 2030:Complete deep space transport. Long Mars simulation missions. Humans on Mars.


Challenges of Spaceflight: LEO and Beyond

75m

109m

~400km

Low Earth Orbit - ISS:Known medical risks, Constant communication,

Access to Earth, Minimum autonomy

6-8 Crewmembers 2-4 Crewmembers

6 month crew missions 30-90 day crew missions

~338m3 habitable volume~25-25m3 habitable volume + 11m3 Orion

Earth LEO of 90 min.Moon NRHO of 7days, 380000km from Earth

Emergency return within hours

Emergency return up to 10 days

~30m

~40m

Near-rectilinear halo orbit

3000km 70000km

Moon – Gateway & surface:Mostly known medical risks (short duration), Small delay in communication, Access to Earth within days, Greater autonomy required

Real-time audio/videoConstant communication with ~5 sec. delaysDifficult remote guiding/tele-operating


Spaceflight stressors and risks

Vestibular system

Cardiovascular system

Fluid redistribution

Musculo-skeletal system

Sensorimotor system

Immune system

Behaviour & performance

Endocrine system

Respiratory system

Confinement

Accelerations

Hostile environment

Changing gravity fields

Distance from earth

Ionising radiation

Lunar dust

Neuro-ocular system

Beau and Alan Daniels


Space Radiation Environment

NASA

Solar Energetic ParticlesSolar Particle Events (SPE)

Coronal Mass Ejections

Galactic Cosmic Rays (GCR)


Constant Solar Wind

Constant Solar Wind

gif by Crazy Picture/CC BY-SA 3.0


Radiation environment during space travelPrimary particles

Solar Particle Events (SPE)

Earth radiation belts

Galactic Cosmic rays (GCR)

87% Protons12% Helium

1% Heavy nuclei100 MeV–100 GeV

Electrons & Protons1k–12k km 1–5 MeV

13k–60k km 10–100 MeV

Secondary particlesShielding

Neutrons

Protons

Electrons

X-rays

Gamma rays

Recoil heavy

nuclei

Radiation sources

92% Protons6% Helium

2% Heavy nucleikeV–100 MeV

Barratt, Baker, Pool, 2019 (modified)


LEO

Stefanov and Evans, 2015

Magnetic AxisRotational Axis

South Atlantic Anomaly (SAA) 200km from Earth

Y. Engbers

NASA

ISS orbital inclination 51.6⁰


NRHO

Bamford, 2017; after Nelson, 2016 and Wilson, 1997


Radiation-induced DNA damage

Hellweg et al., 2020

• Direct ionisations: High-LET charged particles and neutrons

• Indirect ionisations: Low-LETX-rays and γ-rays

Linear Energy Transfer (LET) describes the action of radiation into matter

Relative biological effectiveness (RBE) describes how different particles interact with tissues, given the same amount of

absorbed energy

From Hall et al., 2012 Morgan et al., 2016


Track Structures of Charged Particles

Cucinotta & Durante, 2010


γ

Si

Fe

JC Chancellor et al., 2018; Cengel et al., 2010

Cell fates

Cancer-protective

Cancer-promoting

Growth arrest

Premature

Differentiation

Cell death

Apoptosis

Autophagy

Mitotic

catastrophe

Senescence

Mutations

Chromosomal

Aberrations

Transformation

60 MeV

p+

600 MeV 56Fe

290 MeV 12C

1 GeV 56Fe

X-ray

60Co


How heavy are heavy ions?

Jakob et al., Proc. Natl. Acad. Sci. 2009; Nucl. Acids Res. 2011


Radiation exposure quantities

Radiometric

Dosimetric

Protection

Operational

Number of particles Fluence φ [1/m2]

Deterministic effects

Equivalent Dose HT [Sv]

Ambient Dose Eq. H’ [Sv]

Personal Dose eq. HT [Sv]

Stochastic effects

Effective Dose E [Sv]

Energy absorbed from charged particles

Absorbed Dose D [Gy]

Energy transferred

from uncharged particles

Kerma K [Gy]

x WRRadiation weighting factor

Charged particle

equilibrium

x WT

Tissue weighting factor

x 𝐸µ𝑒𝑛ρ𝑀

x𝑆

ρ𝑀𝑐𝑜𝑙

Directional ambient dose equivalent H’ [Sv]

Personal Dose equivalent Hp [Sv]


Space Weather is getting worse

Schwadron et al., 2014


Let’s put it into perspective…

3,1x M /1 year**

10x

200x

2 weeks in Fukushima exclusion zone

10 000x

Head CT

20 000x

0.1 µSv*

0.5x

100x /1 day

NY to LA 400x

1,75x M /1 year

1,6x M /6 months

12x G /3 years**

Dose to tumour …WAY MORE !

* aka. Banana Equivalent Dose ** estimations


Spaceflight-related exposures

Event Radiation dose level

ISS skin dose solar max. 0.5 mSv/day or 5k

ISS skin dose solar min. 1 mSv/day or 10k

Shuttle average mission skin dose

~4.3 mSv/day or 43k

EVA exposure with passes through SAA

4.5 mSv/event or 45k

Skin dose during 1989 SPE (Shuttle, no EVA)

10 mSv/event or 100k

Apollo 14 (highest skin dose)

14 mSv/mission or 140k

Mir crewmember dose to BFO during 1989 magnetic storm

30 mSv/event or 300k

Skylab 4 (highest skin dose)

178 mSv/mission or 1,78 M

Barratt, Baker, Pool, 2019 (modified)


Dependent on Solar Cycle and

shielding

ISS & exploration missions

Chronic whole body exposure to

low doses

Single energetic particles

Secondary particles

24/7 exposure

Trapped Radiation in

radiation Belts

ISS: intermittent whole body

exposure to low doses

Exploration: Short whole

body exposure

SAA important for dose accumulated on ISS

Belts traversed during exploration

Solar Particle Events (SPE)

Dependent on shielding and solar activity

ISS: protection by geomagnetic

field

Exploration missions: risk of acute whole body exposure to high

doses

Mostly protons

High dose rates possible

Dangerous with insufficient shielding (EVA)



What’s the problem with radiation?

Chancellor at al., 2014

• The effects may occur immediately or/and throughout the

lifetime

• The effects are a function of dose, dose rates and type of

radiation

• Acute effects

- Very large high-energy solar

events

- Estimate ~ 1,4Gy/h

(unsheltered) for 1972 Event

- MILD symptoms IF they

occur at all given doses

• Potential early neurological

effects

- Behaviour or memory

decrements

- Observed only in animal

models

Short term: Mission success

• Cancer

- Space radiation may cause

unique impacts

• Degenerative

- Cardiovascular disease

- Cataracts

• Potential late neurological

decrements

- Behaviour or memory

decrements

- Neurodegenerative disease

- Observed only in animal

models

Long term health


Radiation-induced effectsDeterministic Stochastic

• Severity dependent (“determined”) on the dose

• Effect only when exposure exceeded threshold

• Damage of large amount of cells

• Usually short latency

• Acute radiation syndrome• Chronic post-radiation

syndrome (cataract, radiation dermatitis)

• Sterility

• Probability increases with the dose (not the severity!)

• No “safe” threshold• Damage of single cell can be

enough to cause effect • Manifestation delayed

(typically years)

• Somatic mutation (cancer)• Germline mutation (inherited

genetic disease)• Degenerative/chronic diseases

• Real-time dosimetry• Storm shelter & protocols on

board• Limited medical care on board

• Real-time dosimetry• Radiation Risk Assessment

NASA


How we do it for LEO

Short-term dose limits to prevent deterministic effects

Consensus dose limits for BFO adopted by MMOP

Organ specific equivalent dose limits for BFO

30 Days 0.25 Sv or 2.5 M

Annual 0.50 Sv or 5 M

ESA equivalent dose limits

Organ specific equivalent dose limits for BFO | Eye | Skin

30 Days 0.25 | 0.5 | 1.5 Sv

Annual 0.50 | 1 | 3 Sv

Career dose limit / threshold risk estimate to prevent stochastic effect

ESA career limit of 1 Sv (ICRP 60)

RSA - 10% excess total radiation risk (cancer and non-cancer)

NASA - 3% probability of lifetime excess cancer mortality risk – NASA Space Radiation Cancer Risk (NSCR) Model

ICRP Task Group 115Risk and Dose Assessment for

Radiological Protection of Astronauts

Redefining New Standards for Deep Space Exploration

NASA

After Straube et al., 2010


Risk of Exposure-Induced Death

Probability of dying from radiation induced cancer

Age at exposure

Dose

Background survival rates

Tissue, age & sex specific excess cancer mortality rate

Attainted age


How is it calculated?

LSS incidence rates

US avg. & NS Cancer

DDREF

Radiation quality (solid/leukemia) Track

structure risk cross section

Tissue specific particle spectra & organ dose

eq.

Excess Relative or Additive Risk (ERR/EAR)

Tissue specific cancer rate (mortality/incidence)

REID US avg. NS (age/sex)

HZE nuclei effects can be scaled to γ-

rays

Risk is linear & additive over mixed high & low LET env.

Individual sensitivity is

ignored

Mission/Astronaut Specific Cancer Risk

from Cucinotta et al., 2013


Where is the data coming from?

Life Span Study (LSS) of Atomic Bomb Survivors sex-specific radiation responses

• UNSCEAR 2006 (Stomach, Colon, Liver, Lung, Bladder, Oesophagus, and Brain-CNS)

• Little et al., Radiation Research 169, 660 (2008) (Leukaemia)

• BEIR VII (Breast and Thyroid)

• Preston et al, Radiation Research 168, 1 (2007) (Oral Cavity, Prostate, Ovary, Uterus, and Remainder)

US Astronaut Background Cancer rates

• US cancer registries provide cancer rates for the average US population

• Astronauts are not average

• Adjustments made to average US mortality and cancer rates to estimate rates for a Never Smoker (NS) population


NASA Career Limit 3% REID

REID indicates that 3 people per 100 may die from cancer due to exposure, but it doesn’t tell, if there are other, non-cancer threats, and it doesn’t give recommendations whether it’s worth to take the

risk and if so, who and when will die

Effective Dose Career Limits [Sv] on 1 year mission assuming an ideal case of equal organ dose equivalents for all tissues

Age at exposure Females Males

30 0.6 0.78

40 0.7 0.88

50 0.82 1.0

60 0.98 1.17from Cucinottaet al., 2013


That was just the beginning…

from Cucinotta et al., 2013


Radiation protection in deep space

• Traditional terrestrial protection not applicable in space:➢ Time - at some point you will

always reach a limit

➢ Distance - there is no point source to move away from

➢ Shielding - Energetic and secondary penetrating particles

• New countermeasure strategies➢ Health surveillance including

early disease detection

➢ Compound-based countermeasures

• Redefined radiation dose

• Redefined dose limits to “mission critical”

• Personalised risk assessment with personalized countermeasures

• Less “epidemiological”, more “mechanistic”

• Multidimensional (Cancer, CNS Risks, Chronic & Degenerative Tissue Risks)

We need to know the mechanism and have reliable epidemiology

SCIENCE


Space research

• Exposure platforms

• In-vitro and animal experiments

• Human spaceflight to Gateway, moon and

Mars (limited data, 1 mission (4 crew) per

year)

Research to solve the space radiation problem

Ground analogs

• Epidemiological studies (medical exposures)

• Space radiation simulator (ESA IBER Programme)

GSI.de


Take-home messages

• Radiobiology is complicated

• Bias is everywhere

• Elon Musk won't get to Mars any

soon*

* Round trip, safely

• Radiation is everywhere

• Space weather is a real thing• Nobody is radioresistant

• IR Risk is more than cancer


List of acronyms

ESA European Space Agency

ISS International Space Station

IR Ionizing Radiation

LEO Low Earth Orbit

BLEO Beyond Low Earth Orbit

GCR Galactic Cosmic Rays

SPE Solar Particle Event

NRHO Near-rectilinear halo orbit

EVA Extra-vehicular activity

BFO Blood Forming Organs

RSA Russian Space Agency

NASA National Aeronautics and Space Administration

ICRP International Commission on Radiological Protection

NCSR NASA Space Radiation Cancer Risk

REID Risk of Exposure-Induced Death

CNS Central Nervous System

LET Linear Energy Transfer

RBE Relative Biological Effectiveness


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