Fukushima NPP Disaster and Implications for Human Health - Assessment of Low Dose Radiation Exposure

1. Fukushima
NPP
Disaster
and
Implica6ons
for
Human
Health
Assessment
of
Low
Dose
Radia6on
Exposure
James
P.
Seward,
MD
MPP
FACOEM
Clinical
Professor
of
Medicine
UCSF
Presented
at
US-­‐Japan
Roundtable
October
24,
2013

3. The
Risk
Paradigm
Risk
Management
Risk
Evalua6on
Op6on
Assessment
Op6on
Implementa6on
Monitoring
and
Review
Risk
Assessment
Hazard
Iden6fica6on
Dose-­‐Response
Exposure
Assessment
Risk
Characteriza6on
Risk
Communica2on

4. Core Concepts in Radiation Exposure
• Equivalent Dose measures the biological damage
potential and health risk from radiation
• Equivalent dose is measured in Sieverts (Sv)
• “Low dose” is <0.1 Sv (100 mSv)

5. Natural
Background
Radia6on
Natural
background
radia2on
dose
approx
2
mSv/year
3
(range
1-­‐10
mSv)
without
known
health
effects
0.38
mSv
2.3
mSv
5

6. Average
Natural+
Man-­‐made
Background
Dose
(USA)
6
mSv
Established
Human
Cancer
Threshold
100
mSv
Fatal
Acute
Dose
(LD-­‐50)
4000
mSv

7. Uncertainty
of
dose
response
rela6onship
for
radia6on-­‐induced
cancers
____
Linear
No
Threshold
(
High
Energy)
._._._
Linear
No
Threshold
(Low
Energy)
_
_
_
_
Linear
Quadra2c
(leukemias)
…………
Linear
with
Threshold
Source:
BEIR
VII
7

8. Linear No-Threshold Hypothesis (LNT) for
Cancer Causation
• US
Na6onal
Academy
of
Science
(BEIR
VII):
• “Difficult
to
evaluate
cancer
risk
at
less
than
100
mSv”
• “Risk
would
con6nue
at
lower
doses
without
threshold”
• “Smallest
dose
has
poten6al
to
cause
small
increase
in
risk”
• Predicts
1
person
in
100
gets
cancer
from
dose>
100
mSV
• Errs
on
safe
side
8

9. Concerns
about
the
Linear
No
Threshold
Approach
• Studies
of
areas
with
higher
background
radia6on
show
no
increased
cancer
rates
• Biologic
repair
may
reduce
risk
• UNSCEAR:
“does
not
recommend
mul6plying
low
dose
by
large
numbers
of
individuals
to
es6mate
numbers
of
radia6on-­‐
induced
health
effects
…”
• Example:
100
Sieverts:
Effect
of
1
Sv
to
100
people
≠.001Sv
to
100,000
people

10. The
Health
Physics
Society
“Es6mates
of
risk
should
be
limited
to
individuals
receiving
a
dose
of
50
mSv
in
one
year
or
a
life6me
dose
of
100
mSv
in
addi6on
to
natural
background.”

11. Human
Epidemiology
Shows
Increased
Cancer
Risk
Above
100
mSv
____
Linear
No
Threshold
?
∧
∧
100
mSv
(
High
Energy)
._._._
Linear
No
Threshold
Low
Energy)
_
_
_
_
Linear
Quadra2c
(leukemias)
…………
Linear
with
Threshold
Modified
from:
BEIR
VII
11

12. Health
Concerns
for
>20,000
Fukushima
Workers
• No
Rad-­‐related
fatali6es
or
determinis6c
effects
seen
acutely
•
Less
than
1%
receive
doses>
100
mSv
– Uncertainty
of
dose
measurements
– Small
projected
increased
risk
for
leukemias
and
solid
tumors
– Psychological
concerns
• Ongoing
exposure
poten6al
•
Health
monitoring
12

13. Radio-­‐Iodine
Exposures
near
Fukushima
much
lower
than
Chernobyl
WHO
es6mates
thyroid
cancer
risk
of
most
highly
exposed
female
infant
increases
by
0.5%
(from
0.75%
to
1.25%
life6me
risk)

14. WHO
Preliminary
Dose
Reconstruc6on
Whole
Body—All
Key
Radioisotopes
High
Areas:
10-­‐50
mSv
effec6ve
dose—mostly
external
Lower
areas:
1-­‐10
mSv
effec6ve
dose—mostly
internal

15. Japanese
Food
Radioac6vity
Standards
Highly
Protec6ve
<
100
Bq/Kg
• ~0.075
mSv
dose
to
Japanese
consumer
ea6ng
fish
for
a
year
at
maximal
regulatory
limit
• Naturally
occurring
radia6on
in
fish
(210Po
,
40K
)
a
greater
risk
15

16. Life6me
Cancer
Mortality
Risk
per
Becquerel
(not
adjusted
for
rela6ve
amounts
in
different
fish)
5.0E-­‐08
4.5E-­‐08
Life6me
CA
Mortality
Risk
(per
Bq)
4.0E-­‐08
3.5E-­‐08
3.0E-­‐08
2.5E-­‐08
2.0E-­‐08
1.5E-­‐08
1.0E-­‐08
5.0E-­‐09
0.0E+00
HTO
Cs-­‐134
Cs-­‐137
Sr-­‐90
K-­‐40
I-­‐129
Po-­‐210
U-­‐238
Pu-­‐239
For
fish
mee6ng
Japanese
food
safety
standards
radia6on
dose
from
Po-­‐210
far
exceeds
Fukushima-­‐related
dose

17. Ongoing
Water
Leaks
Are
an
Environmental
Concern
Not
a
significant
health
risk
to
general
popula6on
as
long
as
seafood
safety
standards
are
maintained

19. Mental
Health
Issues
• Surveys
show
high
levels
of
stress
in
adults
and
children
• Fear
of
radioac6vity
and
health
consequences
• Long
las6ng
psychological
health
consequences
in
Chernobyl
evacuees
• S6gma6za6on
• Reluctance
to
discuss
personal
issues
• Con6nued
displacement

20. Summary
of
Health
Implica6ons
for
people
living
near
Fukushima
Dai-­‐ichi
• WHO
es6mates
small
increased
radia6on-­‐related
cancer
risk
that
may
be
difficult
to
measure
–
greatest
risk
is
thyroid
cancer
in
infants
• Psychological
distress
in
the
local
popula6on
has
been
very
high
• Leaks
of
contaminated
water
from
the
NPP
are
not
likely
to
be
significant
health
risk
–
Contribu6on
to
total
radioac6ve
material
in
ocean
likely
to
be
small
rela6ve
to
ini6al
disaster
– Current
food
safety
standards
are
very
protec6ve
– Natural
radia6on
in
seafood
is
higher
than
contribu6on
from
NPP
emissions
in
marketable
fish