Fukushima NPP Disaster and Implications for Human Health

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

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Fukushima NPP Disaster and Implications for Human Health

  1. 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  
  2. 2. 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  
  3. 3. 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)
  4. 4. 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  
  5. 5. Average  Natural+  Man-­‐made   Background  Dose  (USA)                          6  mSv       Established  Human  Cancer  Threshold    100  mSv       Fatal  Acute  Dose  (LD-­‐50)          4000  mSv                              
  6. 6. 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  
  7. 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   8  
  8. 8. 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  
  9. 9. 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.”      
  10. 10. 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  
  11. 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       12  
  12. 12. 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)  
  13. 13. 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      
  14. 14. 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  
  15. 15. 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    
  16. 16. Ongoing  Water  Leaks  Are  an   Environmental  Concern   Not  a  significant  health  risk  to  general  popula6on   as  long  as  seafood  safety  standards  are  maintained  
  17. 17. 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  
  18. 18. 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    

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