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– Erythemia– Decreased blood count– Epilation– Acute Radiation Syndromes (ARS)

• Late– 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.