RADIATION EFFECTS

Stochastic (probabilistic): Cancer, Genetic Effects

Deterministic: Cataracts, Skin Erythema & Burns, Acute Radiation Sickness & Death

Deterministic effects generally occur only at rather high radiation doses (greater than 100 rem) and may be acute or delayed.

Stochastic effects may occur at low radiation dose (though the lower the dose the lower the chance of a detrimental effect) and are always delayed.

The "Linear no-threshold hypothesis" states that the detrimental stochastic effects of radiation extend down to the lowest doses. This CANNOT be proved since we have little direct evidence of harm below about 10 rem.

We usually assume the linear no-threshold hypothesis to be true when making radiation safety decisions. This is essentially erring on the safe side. However, it could be a problem when we go to expensive means to reduce radiation doses below 10 rem when we cannot be sure that any harm is actually being avoided. It also may unjustly bias us to reduce the quality of the radiographic exam to an unacceptable level simply to reduce patient dose. Finally it may cause an exaggerated fear of radiation for both the patient and clinician. You can see that it would be very helpful if we actually knew what was the realistic risk from radiation at low doses. Since we simply do not, the accepted radiation safety practice at the present time is ALARA – radiation doses to patients, radiation workers, and the general public should be as low as reasonably achievable.