Is natural radiation good for you

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Is natural radiation good for you?

• Inaugural lecture
• Professor Steve Jones
• 29 January 2009

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(No Transcript)
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The Radium Palace
Extraordinary biological effects of radon are
based on an exceptional positive energy of
Alpha-radiation that is absorbed by the human
body during the procedure. After the bath a dry
poultice follows and resting on a deckchair. The
radon cure is prescribed by the physician one
bath can be taken without a prior
consultation. Effect analgesic,
anti-inflammatory, bio-stimulating. It stimulates
cells and organs to remedy processes also it
stimulates glands with inner secretion, including
gonads
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Average radiation exposure of the UK
population(total radiation dose 2,700
microSieverts per year)
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Radiation exposure of high rate fish and
shellfish consumers on the Cumbrian coast(total
radiation dose 3,300 microSieverts per year)
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Radioactive decay
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Nuclear stability
ZN 11
Number of protons (Z)
Lead
Tin
Nickel
Number of neutrons (N)
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Origin of the elements
Hydrogen ? Helium Helium ? Carbon
Carbon ? Neon Neon ? Oxygen Oxygen
? Silicon Silicon ? Iron
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Primordial radionuclides

• Potassium-40 (halflife 1.3 billion years)
• Rubidium-87 (halflife 48 billion years)
• Thorium-232 (halflife 14 billion years)
• Uranium-235 (halflife 0.7 billion years)
• Uranium-238 (halflife 4.7 billion years)

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Uranium and thorium decay series
Number of protons (Z)
Number of neutrons (N)
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Uranium-238 decay series
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Radon demonstration
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Cosmogenic radionuclides
Tritium (half-life 12.3 y) - produced from
nitrogen and oxygenBeryllium-7 (half-life 53 d)
- produced from nitrogen and oxygen
Carbon-14 (half-life 5730 y)- produced from
nitrogen and oxygen Sodium-22 (half-life 2.6 y)
- produced from argon
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Radiation doses from natural sourcesUK average -
microSieverts per year
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Absorbed radiation dose - the Gray
A dose of 1 Gray corresponds to the deposition
of 1 joule of energy per kilogram of matter (e.g.
living tissue)
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So what dose do you get from drinking a cup of
coffee?

• 150 ml of coffee drunk at 60oC
• The coffee is cooled by 23oC to body temperature
  (37oC) transferring150 x 23, or 3500 calories,
  of heat energy
• 3500 calories is 3500 x 4.2, or 14,700 Joules
• I weigh about 83 kilos, so thats 14,700 / 83, or
  about 180 Grays
• Or is it..?

• 5 Grays of ionising radiation to the whole body
  is likely to lead to death within 10 to 30 days
  through effects on the bone marrow
• 50 Grays is likely to lead to death within 3 to 5
  days through effects on the gastrointestinal
  tract
• 100 Grays or more is likely to lead to death
  within 48 hours through effects on the central
  nervous system.
• So the Gray is specific to energy deposited in
  tissue by ionising radiation - but why is that
  sort of energy special?

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Size matters - in the quantum world, at least
E hn
E mc2
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The electromagnetic spectrum
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Energy deposition, DNA and LET
2 nm
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Equivalent dose - the Sievert

• Sieverts Grays x radiation weighting factor
• gamma weight 1
• beta weight 1
• alpha weight 20

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Effective dose (also the Sievert)
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Effective dose (also the Sievert)

• Effective Dose (Sv) Sum over all organs and
  radiation types of
• Absorbed dose (Gy)
• x radiation weighting factor
• x tissue weighting factor

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Estimating effective dose
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Internal dosimetry
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Lung dosimetry
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Estimating intakes
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Steps in assessing effective dose
Spatial and temporal variability Modelling
uncertainty
Determine radionuclide concentrations
Individual variation in habits
Weighting factors Model structure and
parameters Physiological and metabolic variability
An inherently uncertain and un-measurable quantity
They were devised to allow doses from different
internal emitters and external radiation to be
summed for comparison with limitsthe results
can only be regarded as providing an approximate
indication of risks to individuals. HPA
consultation on guidance on application of ICRP
recommendations, 2008
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Radiation exposure of high rate fish and
shellfish consumers on the Cumbrian coast(total
radiation dose 3,300 microSieverts per year)
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More direct evidence?

• Direct measurements of radioactivity in exposed
  individuals?
• Possible (and used) in some aspects of
  occupational exposure, only of very limited use
  in environmental exposure
• Look for evidence of ill health in exposed
  populations - epidemiology?
• An important check - but particularly for
  environmental exposure, can be a rather blunt
  instrument..

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Epidemiology - Hiroshima and Nagasaki
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Is natural radiation entirely harmless?

• Darby et al 2006 (Scand J Work Environ Health)
• Combined analysis of 13 European studies of
  residential radon and lung cancer risk
• Showed a 16 increase in lung cancer for every
  100 Bq m-3 radon concentration in the home
• UK action level for radon in homes is 200 Bq m-3
• Gray, Read, McGale and Darby 2009 (BMJ) apply
  these findings to the UK - 1100 lung cancer
  deaths per year related to radon in the home.
• Wakeford, Kendall and Little 2009 (Leukaemia)
• Apply currently accepted risk factors to UK
  natural radiation
• Natural radiation could account for 8 to 30 of
  childhood leukaemia cases
• Not confirmed to date by epidemiological
  observation (and would require a large and well
  designed study to test the hypothesis)

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Conclusions

• Natural radiation isnt good for you - but think
  of it as a risk weve learned to live with
• Comparisons between natural and anthropogenic
  radiation exposure are based on good science, but
  also on judgements and assumptions that are hard
  to test rigorously
• The public and political sensitivities
  surrounding nuclear power guarantee that there
  will be continued debate on low level radiation
  risks but..
• Entrenched and polarised positions produce a
  climate inimical to good scientific judgement (or
  any other sort of judgement) and consequently bad
  decision making