Fukushima NPP Disaster and Implications for Human Health
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Transcript of Fukushima NPP Disaster and Implications for Human Health
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
Risk Assessment Hazard Iden6fica6on Dose-‐Response Exposure Assessment Risk Characteriza6on
Risk Management Risk Evalua6on Op6on Assessment Op6on Implementa6on Monitoring and Review
Risk
Communica2on
The Risk Paradigm
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)
Natural Background Radia6on Natural background radia2on dose approx 2 mSv/year (range 1-‐10 mSv) without known health effects
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2.3 mSv 0.38 mSv
3
Average Natural+ Man-‐made Background Dose (USA) 6 mSv Established Human Cancer Threshold 100 mSv Fatal Acute Dose (LD-‐50) 4000 mSv
____ Linear No Threshold ( High Energy) ._._._ Linear No Threshold (Low Energy) _ _ _ _ Linear Quadra2c
(leukemias) ………… Linear with Threshold
Uncertainty of dose response rela6onship for radia6on-‐induced cancers
Source: BEIR VII 7
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
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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
“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.”
The Health Physics Society
____ Linear No Threshold ( High Energy) ._._._ Linear No Threshold Low Energy) _ _ _ _ Linear Quadra2c
(leukemias) ………… Linear with Threshold
Human Epidemiology Shows Increased Cancer Risk Above 100 mSv
Modified from: BEIR VII
? ∧ ∧
100 mSv 11
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
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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)
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
Japanese Food Radioac6vity Standards Highly Protec6ve
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< 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
Life6me Cancer Mortality Risk per Becquerel
(not adjusted for rela6ve amounts in different fish)
0.0E+00
5.0E-‐09
1.0E-‐08
1.5E-‐08
2.0E-‐08
2.5E-‐08
3.0E-‐08
3.5E-‐08
4.0E-‐08
4.5E-‐08
5.0E-‐08
HTO Cs-‐134 Cs-‐137 Sr-‐90 K-‐40 I-‐129 Po-‐210 U-‐238 Pu-‐239
Life6me CA Mortality Risk (per Bq)
For fish mee6ng Japanese food safety standards radia6on dose from Po-‐210 far exceeds Fukushima-‐related dose
Ongoing Water Leaks Are an Environmental Concern
Not a significant health risk to general popula6on as long as seafood safety standards are maintained
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
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