Risk and Hazards

• Background Radiation


  Naturally-occurring radiation that is the main source of exposure for most people
• Levels of background radiation typically range from about 1.5 to 3.5 millisievert per year but can be more than 50 mSv/yr
• The highest known level of background radiation affecting a substantial population is in Kerala and Madras States in India where some 140,000 people receive doses which average over 15 millisievert per year from gamma radiation in addition to a similar dose from radon
• Comparable levels of high background radiation occur in Brazil and Sudan, with average exposures up to about 40 mSv/yr to many people
• Several places are known in Iran, India and Europe where natural background radiation gives an annual dose of more than 50 mSv and up to 260 mSv (at Ramsar in Iran)
• Lifetime doses from natural radiation range up to several thousand millisievert
• There is no evidence of increased cancers or other health problems arising from these high natural levels of background radiation
• Man-Made Radiation


  Ionising radiation generated in a range of medical, commercial and industrial activities
• The most familiar and largest source of man-made radiation exposure is medical X-rays
• Natural radiation contributes about 88% of the annual dose to the population and medical procedures most of the remaining 12%
• Natural and most artificial radiations are not different in kind or effect
• Protection from Radiation


  Ways in which people are protected from identified radiation sources
• Protection from Radiation


  1. Limiting time

  2. Distance

  3. Shielding

  4. Containment
• Radiation is very easily detected using a range of simple, sensitive instruments
• An Introduction To The Health Effects of Radiation
• Radiation Protection Standards


  Based on the conservative 'linear no-threshold (LNT) hypothesis' which assumes risk is directly proportional to dose, even at the lowest levels
• Wilhem Conrad Roentgen discovered X-rays


  1895
• The LNT hypothesis is recommended for radiation protection purposes only, and cannot properly be used for predicting the consequences of actual exposure to low levels of radiation
• Wilhem Conrad Roentgen received the first Nobel Prize for physics


  1901
• Much of the evidence for radiation protection standards derives from the atomic bomb survivors in 1945, who were exposed to high doses incurred in a very short time
• Marie Curie, Pierre Curie, and Henri Becquerel were awarded the Nobel Prize in physics for their contributions to understanding radioactivity, including the properties of uranium


  1903
• In setting occupational risk estimates, some allowance has been made for the body's ability to repair damage from small exposures, but for low-level radiation exposure the degree of protection may be unduly conservative
• Enrico Fermi and others started the first sustained nuclear chain reaction in a laboratory beneath the University of Chicago football stadium


  1942
• ICRP Recommendations


  Justification, Optimisation, Limitation
• Nuclear bombs dropped on Japan

  1945
• Solar radiation wavelength


  • Visible light – 400 to 760 nm
  • Ultraviolet radiation (UV) - >400 nm (sunburn)
  • Infrared radiation - <760 nm (heat)
• The ICRP recommends a maximum permissible dose for occupational exposure of 20 millisievert per year averaged over five years (ie 100 millisievert in 5 years) with a maximum of 50 millisievert in any one year
• For public exposure, the ICRP recommends a limit of 1 millisievert per year averaged over five years
• UV radiation


  • Stimulates melanin (dark pigment) that absorbs UV protecting cells
• Typical breakdown of radiation sources

  • 48% Radon
  • 4% Thoron
  • 10% Cosmic
  • 14% Gamma
  • 11% Medical
  • 12% Internal
  • 0.4% Miscellaneous
  • 0.2% Occupational
  • 0.4% Fallout
  • 0.04% Nuclear Discharges
• • 2 to 3 million non-malignant skin cancers
  • 130,000 malignant melanomas
  • Sunburn – acute cell injury causing inflammatory response (erythema)
  • Accelerates aging process
• Radium Girls: '"Not to worry," their bosses told them. "If you swallow any radium, it'll make your cheeks rosy."'
• 1. rays


  A form of energy, similar to light and radio waves, that have enough energy to pass through the body
• The women at Radium Dial sometimes painted their teeth and faces and then turned off the lights for a laugh
• Radium discovered by Marie Curie


  1898
• 1. rays


  • Unlike light waves, x-rays have enough energy to pass through your body
  • As the radiation moves through your body, it passes through bones, tissues and organs differently, which allows a radiologist to create images of them
• Radium Therapy - used to treat arthritis, stomach ailments and cancer


  1900-1930
• Radiologist


  A specially trained physician who can examine x-ray images on a monitor
• Radium Therapy was accepted by American Medical Association
• Use of radium on watch dials


  WWI