The health risks of exposure to internal radiation. Korea National Assembly Seoul 22 nd August 2015

Transcription

1 The health risks of exposure to internal radiation Korea National Assembly Seoul 22 nd August 2015

2 Christopher Busby Green Audit UK/ Environmental Research SIA, Riga, Latvia Scientific Secretary: European Committee on Radiation Risk, ECRR --Previously-- UK Ministry of Defence Depleted Uranium Oversight Board (DUOB) UK Dept of Health Committee Examining Radiation Risks from Internal Emitters (CERRIE) Leader: European Union Science/ Policy interface; Policy Information Network for Child Health and the Environment (PINCHE). Visiting Professor, University of Ulster UK Guest Researcher, University of Liverpool UK Guest Researcher, Jacobs University, Bremen, Germany Guest Researcher, Federal German Agricultural Research Laboratory Visiting researcher Julius Kuehn Institute, Braunschweig, Germany

3 Seen here looking for Depleted Uranium with a scintillation counter. Serbian tank in Kosovo 2001

4 Summary: Sources of man-made radiation exposure Enhancement of natural radioactive pollution (Uranium mining and processing, nuclear fuel cycle, depleted uranium weapons, natural gas and oil production, phosphate fertilisers, radium dials); Uranium and Radium Dispersion of fission products (Caesium-137, Plutonium-239, Strontium-90, Iodine-131, etc.). Main examples: 1. Atmospheric weapons tests, licensed nuclear power station and reprocessing releases (Sellafield, La Hague), nuclear accidents (Chernobyl 1986, Windscale 1957 etc),research uses of radioisotopes 2. Medical exposures (X-rays, cancer therapy)

5 Main types of Radiation Electromagnetic radiation is an energetic form of light: this includes gamma radiation and X-rays. Gamma rays pass right through you and the electron tracks produced are sparsely ionising. Charged particle radiation: includes energetic electrons (beta) and slower highly ionising alpha particles. These are released from radioactive materials like natural Uranium, Potassium-40 and also man-made substances called radionuclides, like Plutonium-239, Caesium-137 and Strontium-90. These are made by the fission of Uranium-235 and since 1945 have contaminated the entire biosphere. Beta tracks vary in their ionising density but alpha tracks are highly ionising.

6 1. Ionising radiation, whatever its source or type, is absorbed by materials with the creation of charged particle tracks which leave structured paths of ions and reactive chemical species. 2. It is these fragments that react with DNA and cause fixed mutations and cancer.

7 The target for radiation effects is the cellular DNA

8 It is mutation of the DNA that leads to cancer, birth defects and other diseases

9 . Internal radiation from Uranium and Uranium fission Fission products are versions of natural chemical elements which are radioactive. They become incorporated into the body through the food chain and inhalation. Many of them bind to DNA and have local serious genetic effects which are not predicted by the scientific risk model which is the basis of all present exposure risk standards, that of the International Commission of Radiological Protection (ICRP). For this reason, in 1997 I helped start an alternative risk committee, the European Committee on Radiation Risk (ECRR), whose model was published in 2003 and updated in This model predicts and explains the effects of internal radiation exposure. It has now been published in Japanese, Russian, French. Since Fukushima it is a free download from the website:

10 Examples of internal exposures Examples of common contamination fission products considered to be serious health hazards by ECRR include Strontium-90, Plutonium-239, Barium-140, Tellurium-132/Iodine-131 and Tritium. ECRR also has concluded that Uranium-238, which although natural, has become enhanced in its dispersion and character by man-made activity is a seriously underestimated hazard due to its chemical affinity for DNA and its high atomic number photoelectron conversion. Other enhanced internal exposures include Radium contamination from oil and gas production. The EU radiation research group MELODI, led by the French IRSN has recently ( March 2015) acknowledged the dangers of Uranium by investing in a huge research effort on internal Uranium exposure

11 Radiation exposure and health Health effects modelled on the basis of cancer yield in survivors of Hiroshima and Nagasaki bombs. This is the model of the International Commission on Radiological Protection (ICRP) In this model, the numbers of cancers in the survivors who were exposed to a single large acute EXTERNAL flash of gamma radiation are correlated with the ABSORBED DOSE and a straight line is drawn between this yield and no dose. Linear No Threshold LNT. The method is based on the assumption that all cells in the body receive the same number of radiation tracks. But this is not a valid assumption for INTERNAL radiation where track density varies from place to place.

12 But doses are based on EXTERNAL EXPOSURE ICRP phantom: body is modelled as a bag of water and radiation is assumed external. ABSORBED DOSE is ENERGY divided by MASS, Joules/Kg = Gray This method gives same dose for warming yourself in front of a fire or eating a hot coal.

13 A real hot coal - micron diameter particles of Plutonium in a rat lung: alpha stars

14 It is now universally acknowledged that radiation effects are nor due to whole body exposure but due to DNA damage. So the target is not even the cell, but is mainly the chromosomal DNA. It is therefore the dose to the DNA that is relevant for radiation protection. There are specific mechanisms that enhance the ionisation at the DNA. All cellular DNA including bound water is 1/87 th of the cell by mass.

15 The Linear assumption is also wrong: (from Busby 2013)

16 Dose the key issue in radioprotection. The misunderstandings about the quantity Absorbed Dose are fundamental to the understanding of the health effects of exposure to radioactive contamination, from Hiroshima to Fukushima, from Atmospheric Test fallout effects to Nuclear plant releases to Chernobyl and Fukushima.

17 UK Health Protection Agency Dose Table (msv) Dental X-ray Transatlantic flight 0.07 Nuclear worker annual average 0.18 CT scan of head 1.4 UK average annual 2.7 CT chest scan 6.6 blood cell changes are measurable 100 No cancer detectably predicted 100 Acute deterministic effects 1000 Death in 50% exposed 5000

18 But these are doses based on average energy in large volumes of tissue from whole organs to whole body; averaged over more than 1kg. Dose to the cell or to the DNA is very large from internal exposures. Exposure Alpha track to the cell U-238 or Pu- 239 Dose to DNA from phosphate bound Uranium decay Dose to DNA from single Tritium decay in cell Phantom photoelectron amplification by Uranium/DNAP Dose >300mSv >1000mSv 5mSv >200,000 times natural background Gamma dose at the DNA.

19 LOW DOSES? Doses to 10m cell from internal a- decay (5MeV per decay) event msv Example Single decay 385 msv Any alpha emitter Sequential decays Hot particle 1m diameter Warm particle 1m 1540 msv per decay 570 msv per minute 4.4 msv per day Th-228, Ra-224, Rn- 220, Po-216 Pu-239 U-238 ignoring b daughters and photoelectrons

20 This is addressed in: Busby Intech 2013 Busby Christopher (2013). Aspects of DNA Damage from Internal Radionuclides, New Research Directions in DNA Repair, Prof. Clark Chen (Ed.), ISBN: , InTech, DOI: / Available from: This 50 page article reviews the problem of external and internal doses discussing the evidence and citing the previous literature.