Transcript Dose Limits for Exposure to Ionizing Radiation

Dose Limits for Exposure to
Ionizing Radiation
Sherer
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.
Radiation Safety Program
• All facilities must have a radiation
protection/safety program in place.
• Radiation Safety Committee
– Radiation safety Officer (RSO)
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.
Radiation Induced Responses
• Non-stochastic
– Deterministic
– Directly related to the dose received, threshold
• Early
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Erythemia
Decreased blood count
Epilation
Acute Radiation Syndromes (ARS)
• Late
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Cataracts
Fibrosis
Sterility
Organ atrophy
• 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
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.
Occupational MPD
• 50 mSv or 5 rem annually
• Pregnant
– 0.5 mSv per month
– 5 mSv for the entire pregnancy
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
Radiation Hormesis
• The potential that small radiation exposure
is actually beneficial.