Dose Limits for Exposure to Ionizing Radiation

1. Dose Limits for Exposure to Ionizing Radiation Sherer

2. Effective Dose Limiting System • The idea that exposure to radiation can/may induce cancer. • The result is that radiation protection guidelines are based on the possibility of getting cancer not some other effect.

3. Radiation Safety Program • All facilities must have a radiation protection/safety program in place. • Radiation Safety Committee • Radiation safety Officer (RSO)

4. Effective Dose Limiting System • Looks to establish the upper limit of exposure to ionizing radiation resulting in a negligible risk of injury or genetic defect. • Can be whole body, partial body (extremity, eye) and individual organs. • Non-stochastic (deterministic) and stochastic (probabilistic) • Occupational limits are based on comparing outcomes against other occupational hazards.

5. Radiation Induced Responses • Non-stochastic • Deterministic • Directly related to the dose received, threshold • Early • Erythemia • Decreased blood count • Epilation • Acute Radiation Syndromes (ARS) • Late • Cataracts • Fibrosis • Sterility • Organ atrophy

6. Stochastic • Probabilistic • Mutational, non-threshold, randomly occurring, all or nothing • The greater the dose the greater the chance of the effect occurring. NOT is it going to occur. • Cancer and genetic effects

7. Basis for Effective Dose Limiting System • While we have already discussed the fact different forms have radiation have different effects (equivalent dose) some tissues are more sensitive than others. • Tissue weighting factor allows overall risk to be determined.

8. Occupational MPD • 50 mSv or 5 rem annually • Pregnant • 0.5 mSv per month • 5 mSv for the entire pregnancy

9. Public MPD • 1 mSv or 0.1 rem or 100 mrem • Educational exposure • 1 mSv or 0.1 rem annually • Notice it is the same as the general public

10. Radiation Hormesis • The potential that small radiation exposure is actually beneficial.