1. Radiation and Human Health
Key Issues in Low Dose Radiation Exposure for Fukushima Disaster
James P. Seward, MD MPP
Clinical Professor of Medicine, UCSF
Medical Director
Lawrence Livermore National Laboratory
November 12, 2012

2. Issues to Discuss Types of Radiation effects Pathways of exposure
Linear no threshold dose model for cancer
Radiation Cancer Epidemiology
Thyroid --Solid Tumors --Leukemia
Health Implications for Workers and Residents

3. Radiation Dose Concepts
Adsorbed dose (Gray, Gy) is absorption of radiation energy per unit mass of tissue Gy = 1 Joule per kilogram
Equivalent dose (Sievert, Sv) adjusts for biological damage by different types of ionizing radiation using a “quality factor”
Most exposures in this presentation are:
Low Dose (<0.1Gy = 100 mGy)
Low Linear Energy Transfer (LLET) radiation
γ, β, and X
1 Gy = 1 Sv (I-131,Cs-137, Sr-90)

4. Radioactivity
Becquerel (Bq) = 1 nuclear disintegration/second (1 Curie = 3.7 x 10E10 Bq)
Becquerels from ingestion or inhalation can be converted into equivalent dose using radionuclide, organ, and age conversion factors
Example: Bq of CS-137 ingested by an adult = 1.3 E-06 Sv whole body internal dose

5. Natural Background Radiation
Natural background radiation dose approx 2 mSv/year (range 1-10 mSv) without known health effects 3
0.38 mSv
2.3 mSv
Per NCRP-160 (2009), average dose from nat. background in US is about 3.2 mSv.

6. Human Contributions to Background Dose
3 mSV

7. Lethal, Worker, and Background Doses
Observable deterministic effects (e.g., beginning of Acute Radiation Syndrome) may occur at around 250 to 500 mSv (25 to 50 rads)

8. Environmental Pathways for Radiation Exposure
Internal Dose from radioactive materials in the air

9. Response to Radiation
Deterministic effects : early or late effects that have dose-effect relationship, i.e., a threshold dose – increase in effects with increasing dose
Acute Radiation Syndrome
Skin Burns
Cataracts
Developmental effects (IQ, microcephaly)
Stochastic effects : long-term random or chance effects - relationship, no lower threshold dose for effects
• Risk of Cancer
• Heritable Genetic Defects (observed in lab animal studies—not demonstrated in humans)
Modified from REAC/TS

10. Approximately 160 Deaths or Illnesses from
Acute Radiation Syndrome among Chernobyl Workers
The LD50 for humans is 3-4 Gy for young adults without medical
intervention. EJH, Radiobiology for the Radiologist, 4th Edition,

11. Posterior Cataracts Recent Evidence for lower threshold
Deterministic Effects
Posterior Cataracts Recent Evidence for lower threshold
Skin Burns
Threshold 5 Gy
Sterility M>3.5 Gy
F >2.5 Gy
Cardiovascular
Increased rates of Stroke
and Atherosclerotic Disease
In Utero Mental Retardation
Malformations

12. What is the dose response relationship for radiation-induced cancers?
____ Linear No Threshold
( High Energy)
._._._ Linear No Threshold
(Low Energy)
_ _ _ _ Linear Quadratic
(leukemias)
………… Linear with
Threshold
Source: BEIR VII

13. Linear No-Threshold Hypothesis (LNT) for Cancer Causation
Assumes that cancer risk is proportionate to dose, no matter how small
No threshold for risk—best scientific assumption of reality
Derived primarily from extrapolation of studies of
high dose rate, high linear transfer radiation
(Hiroshima & Nagasaki, Medical Radiation Therapy)
Intended for radiation
safety standard setting
Errs on safe side
“There is no safe level of radiation dose” is as meaningful as “There is no safe level of exposure to the sun.”

14. Human Epidemiology Studies Support Linear Dose Response for solid tumors at doses above 100 mSv
Estimated excess lifetime risk of radiation-related cancer mortality %/100mSv
Japanese cancer mortality risk in unexposed populations 26% (males) and 16% (females)
Cancer mortality Risk for male exposed to 100 mSv would be ~26.05%
Increased Risk for radiation exposed Infants and Children
Some Japanese workers at Fukushima-NPP1 have exceeded 250mSv
Need visual
Can elim statement about workers if keep worker slide later

15. Low Dose Radiation cancer effects are not certain in epidemiological studies
80% Hiroshima & Nagasaki survivors exposed to <100mGy
Survivor studies show solid tumor dose response over 0 – 150 mGy range
But…high dose rate of neutron and gamma
Low dose occupational and medical radiation studies generally negative for cancer increase
Occupational: UK, 3-country, Mayak (Russia)
Wide uncertainties
Suggest trend for leukemia

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

17. Transmissible Reproductive effects
Hereditary genetic diseases
(stochastic effect)
not demonstrated in 30,000
children of Hiroshima and Nagasaki survivors
mouse data demonstrate possibility for these
effects at >250mSv exposure
ratio of induced to spontaneous mutations small
at low dose levels
Ovaries can repair minor genetic damage

18. Radiation Damage to Chromosomes
Indirect damage
Radiation creates highly reactive OH free radicals
75 percent of radiation-caused DNA damage is due to OH free radical.
Direct damage
DNA molecule is struck by radiation, ionized, resulting in damage.

19. Chromosome Damage
Interchange between two chromosomes forms a chromosome with two centromeres and fragment, followed by replication.

20. Potential Biologic Factors with Radiation Carcinogenesis
DNA repair
Adaptation
Bystander effects
Impacts on
suppressor genes
Tumor initiation
monoclonal hypothesis

21. Chernobyl vs.Fukushima
Complete meltdown/fire
Very high emissions
Broad Range of radionuclides
No local Iodine prophylaxis
Delayed evacuation
Prolonged regional low dose
exposure
Consumption of
contaminated food and dairy
Subsequent collapse of USSR
complicates research
Limited reactor compromise
Fewer emissions
narrower range of radionuclides
Limited Iodine—need unclear?
Progressive, but prompt evacuation—miscalculation on plume
Early restrictions on food products
including dairy and fish
• Early efforts to begin dose
reconstruction
DIFFERENCE BETWEEN ATOMIC BOMB AND REACTOR
- INSTANTANEOUS EXTERNAL RADIATION
-REACTOR—GREATER PROPORTION INTERNAL RADIATION ESPECIALLY RADIOIODINE
ECONOMIC COLLAPSE OF USSR ADDED MANY COMPLICATIONS TO HEALTH ASSESSMENT AND CONFOUNDING PUBLIC HEALTH ISSUES
CURRENTLY CONTAMINATED ZONE FALLS PRIMARILY IN 3 COUNTRIES ( UKRAINE, BELORUS, RUSSIA) AND THAT POSES EXTRA LOGISTICAL DIFFICULTIES FOR LONG TERM EPIDEMIOLOGICAL STUDY
OPEN REACTOR CORE AT CHERNOBYL AND PROLONGED FIRE GENERATE GREATER RANGE OF RADIOACTIVE FISSION PRODUCTS

22. Thryoid Cancer-- Chernobyl
Iodine day T 1/2 –Thyroid gland
Average thyroid dose- children near
Chernobyl = 1.4 Gy
Over 6000 Cases –few fatal
Young children highest excess
relative risk (ERR) = 11
ERR declines with age at exposure
little risk for adults
ERR persists as individuals age
THYROID CANCER FROM CONCENTRATION OF RADIOACTIVE DOSE IN THRYOID. BOTH INHALED AND INGESTED ( MILK/FOOD)
RESIDENTS AROUND CHERNOBYL HAD NO WARNING OF RISK FOR SEVERAL DAYS AFTER RELEASES BEGAN
IODINE PILLS CAN BLOCK UPTAKE OF IODINE 131, BUT NONE DISTRIBUTED
INCREASED # OF CASES OF THYRIOD CANCER BEGAN APPEARING SEVERAL YEARS AFTER INCIDENT NOW > 6000 AND CLIMBING
RISK IS VERY AGE DEPENDENT—UNDER 4 YEARS OLD 10 X/GRAY BUT ONLY 2X FOR 20 YEAR OLD. UN Scientific Committee on Effects of Atomic Ratiation concludes that overall there is little evidence for increased risk of thyroid cancer in people exposed as adults.

23. Estimates of Thyroid Equivalent Dose in Japan (WHO Preliminary Assessment)
Exposure in most of Fukushima mSv --primarily inhalation --WHO
- Tashiro(2011) Max 35mSv in children
- Tokonami(2012) Max 23mSv in children
Localized area with mSv
to infants< 1 year old
Rest of Japan 1-10 mSv-- primarily ingestion
Chernobyl data: increased cancer risk >50 mSv

24. WHO Preliminary Dose Reconstruction Whole Body—All Key Radioisotopes
High Areas: mSv effective dose—mostly external
Lower areas: 1-10 mSv effective dose---mostly internal

25. Health Concerns for >20,000 Fukushima Workers
Exposures (mostly internal) up to 670 mSv at beginning of reactor accident (no KI) (INPO Nov. 2011)
UNSCEAR Preliminary report:
167 workers exposed over 100mSv (6 >250mSv)
Uncertainty of dose measurements
No clinically observable effects
Psychological impacts
Ongoing worker health
monitoring needed

26. International Commission on Radiological Protection
“Because of the uncertainty on health effects at low doses the Commission judges that it is not appropriate, for the purposes of public health planning, to calculate the hypothetical number of cases of cancer…that might be associated with very small radiation doses received by large numbers of people over very long periods of time.”
ICRP Pub. 103; 2007

27. Estimates of Total Cancer Create Controversy
Stanford Study (Ten Hoeve and Jacobson: Energy Env. Sci 2012: )
130 additional fatal cancers worldwide, mostly Japan
Wide range 　cancer deaths
Additional 180 ( ) non-fatal cancers
Uncertainties in dose estimation, exposure assumptions, etc.
Difficulty in detection of small numbers in epidemiological studies

29. Ingested Cesium Radionuclides Principal Source of Long term Radioactivity uptake
Biological half life:~ 110 days in adults ~ 50 children
Cs 137 Rad T ½ = 30 years Cs134 Rad T ½ = 2 years
Uptake in vegetables, starches (rice) and seafood (fish, seaweed)
Marshall Islands (US Nuclear Tests) showed most exposure to be from terrestrial food (effective half life 12-20yrs )
Only 0.1% total human radiation exposure from marine sources (integrated over 30 years)
Effective half life (radiological/biological) in reef fish 9-12 years
Japan has recently lowered allowable Cs levels in food, including fish to 100 Bq/kg to keep population dose <1mSv/yr

30. Questions?

32. Background – Science Program
UNCLASSIFIED
Background – Science Program
Cesium-137 is the main contributor to the present-day nuclear test- related dose for resettled and resettling populations in the Marshall Islands
About 85 to 90 % of the dose delivered to islanders from nuclear test- related fallout contamination in the environment is derived from ingestion of Cesium-137 contained in locally grown foods, and the other 10 to 15 % is due to external exposure from residual Cesium-137 in soil
UNCLASSIFIED

33. Effective dose (Sievert, Sv) weights equivalent dose by tissue-specific factors to create a dose figure that standardizes risk

34. Childhood Thyroid Cancer Incidence Belarus (Children <10 yrs old)
Source: UNSCEAR 2008

35. Thyroid Cancer and Chernobyl
Papillary Cell type
Despite tendency to metastasize, treatable with low mortality 1%
Cases will continue to accumulate for years to come
Based on Chernobyl studies prophylaxis with iodine tablets recommended for
anticipated Iodine 131 dose > 50 mSv

36. Other Cancers in regions around Chernobyl (consider latency period…)
Leukemia
Expected as early effect based on Atomic Bomb survivor experience—especially in children
No definite association with Chernobyl victims
Suggestive effect for childhood leukemia in contaminated areas of Russia
Breast Cancer and other solid tumors
Several studies, but no clear trend for Breast Cancer
Possible increase in Russian study

37. Health Effects in 600,000 Rescue Workers/ “Liquidators” at Chernobyl
Acute Radiation Syndrome
28 deaths 1st year…20+ subsequently
130 illnesses from Acute Radiation Syndrome
Cancer effects—No consistent pattern of increase
Suggestion of leukemias and dose-related increases in solid tumors in Russian Studies
Increased posterior sub-capsular cataracts at doses lower than previously documented
Possible increase in cardiovascular disease

38. Woods Hole Oceanographic Institute study concluded that doses from Fukushima radionuclides in contaminated fish would be
far below doses from naturally occurring radionuclides (mostly Po-210) in same fish.

39. Radiation Doses around Fukushima appear be much lower than Chernobyl
Importance of completing Fukushima Health Survey and reconstructing radiation dosimetry
Differing survey results:
Thyroid
Government: 1080 children in Iwaki and other prefectures highest dose 35 mSv
Hirosaki University: 65 people, highest adult 87 mSv
highest child 47 mSv.
Whole body
Fukushima Prefect. Gov.: 10,468 people, highest 23 mSv

40. Cesium—a persistent health concern around Fukushima
Cs year half-life decays by β, γ
Biological half life 110 days
Behaves like potassium in human body, more heavily concentrated in muscle tissue
Taken up from soil by plants (rice,vegetables)
Japan has recently lowered allowable Cs levels in food to 100 Bq/kg to keep population dose <1mSv/yr

41. Implications for Japan
Dose reconstruction and identification of population at risk for thyroid cancer
Risk for all cancers likely to be low and difficult to assess epidemiologically
Lifespan studies of exposed groups
Special attention to medical surveillance of plant workers
Challenging of regaining trust, targeting appropriate services to the right population, maximizing benefit, minimizing harm

42. Typical Doses of Diagnostic X-Ray Procedures
Conventional X-ray (chest, bone) mGy
Conventional Complex X-rays (GI, IVP) mGy
Computed Tomography mGy
Angiography mGy
with intervention (stent) mGy

43. Cardiovascular disease
Increased risk of cardiovascular death from high dose exposure (MI and stroke)
in long-term atomic bomb survivors
HTN, high cholesterol
patients treated with radiotherapy to chest (Hodgkins, breast cancer)
Little evidence of increased risk from occupational studies
Possible mechanisms:
Microvascular damage
Inflammation

46. Increasing Diagnostic X-Ray