Radiation Risks
The BEIR report VII
Defines “low level” radiation as a range from near zero up to 100 milliSieverts (mSv)
- 30-40 times annual natural background exposure
- 10 times that of a CT scan
- 1000 times that of a chest X-Ray
Linear No Threshold Theory
- According to the Linear No Threshold (LNT) theory, the risk of developing radiation induced cancer (stochastic effects) increases with increasing dose.
- This model has been validated at higher acute radiation doses (>100mSv) from the atomic bomb survivors.
- The dose level at which there is a significant risk is not known, but for radiationprotection purposes, it is assumed that there is a linear risk down to “0” dose.
- For low dose exposures, ≤100 mSv per year, the risk profile is open to discussion.
- Different dose risks models have been proposed, going from increased risks to benefits!
- The Health Physics Society stated recently that the LNT theory cannot be used for risk cancer estimates.
ALARA Principle
- Irrespective of the LNT debate we have to follow best practices and keep radiation exposures and doses “As Low As Reasonably Achievable”.
- This is the ALARA principle which means making every effort to maintain exposures to ionizing radiation as far as below the dose limits as practical.
- Taking into consideration the state of technology and the cost of improvements in relation to benefits to public health and safety.