Hazard Awareness - Radiation
McMaster University's Radiation Safety Program is outlined in RMM 700.
The University delegates the authority and responsibility for ensuring compliance with radiation safety legislation to Health Physics (HP) and the Health Physics Advisory Committee (HPAC).
The HPAC is also responsible for the administration of McMaster University's radiation safety program.
In fulfilling this responsibility, Health Physics publishes a Radiation Safety Manual specific to safety considerations critical in dealing with the ionizing radiation associated with radioisotopes and X-rays.
Health Physics can be contacted at x24226.
Radiation can be characterized as either ionizing or non-ionizing.
The risk posed by various forms of radiation stems from their tendancy to deposit energy into the materials they encounter.
Ionizing radiation is sufficiently energetic that it has the potential to knock electrons from atoms or molecules.
It includes alpha and beta particles, as well as gamma, X-ray, and UV photons.
In living tissue, interaction with ionizing radiation can produce damaging structural changes.
Subjected to a sufficient dose, whole organs can cease to function altogether.
Table 1, modified from the Health Physics Radiation Safety Manual, illustrates permissable ionizing radiation exposure levels for the general public according to Ontario guidelines.
| Dose Location | Permissable Annual Exposure (General Public) | |
|---|---|---|
| milliSieverts (mSv) per year | rem (= 0.1 mSv) per year | |
| Whole body | 5 | 0.5 |
| Lens of the eye | 15 | 1.5 |
| Any single organ | 50 | 5 |
| Hands and feet | 50 | 5 |
Table 2, also from the Radiation Safety Manual, indicates the biological effects of various doses of ionizing radiation.
| Dose (mSv) | Effect |
|---|---|
| 0 to 250 | No detectable effects. |
| 250 to 1000 | Slight blood changes with no recovery within a few months. Delayed effects possible, but very serious effects very improbable. |
| 1000 to 2000 | Nausea and fatigue. Blood changes with delayed recovery. |
| 2000 to 3000 | Nausea and vomiting on first day. Latent period up to a few weeks, then malaise, sore throat, diarrhea. Recovery likely within 3 months for healthy individuals. |
| 3000 to 6000 | Nausea and vomiting within a few hours. Latent period up to 1 week, then malaise, fever, hemorrhage, loss of weight, sore throat. Death to about 50% of individuals receiving about 3500 mGy. |
| 6000+ | Symptoms similar to above, but probable death for 100%. |
In any case of known or suspected exposure to ionizing radiation, report immediately to your supervisor and Health Physics (x24226).
Radioactive isotopes
Nuclear materials are controlled federally by the Canadian Nuclear Safety Commission (CNSC).
Radioisotopes represent a risk due to the biological dose effects mentioned above.
The hazard is exacerbated by contamination risks associated with radioisotope storage, handling, and disposal.
All personnel working with radioactive materials are required to attend training provided by Health Physics.
All laboratories in which radioactive materials are to be stored must must possess a valid permit, obtained through Health Physics subject to assessement of the laboratory.
Warning signs must be posted.
No food or drink is permitted in laboratories housing radioactive materials.
Additional regulations apply to pregnant women who work in laboratories housing radioactive materials.
Please see the Radiation Safety Manual for additional information.
X-ray radiation
X-ray radiation safety in Ontario is legislated under Regulation 861.
McMaster University's X-ray radiation safety program is outlined in RMM 701.
Access to McMaster University X-ray facilities is limited to authorized personnel who have completed the X-ray Safety Training course provided by Health Physics.
The CEDT operates two X-ray systems.
The two systems incorporate interlocked sheilding mechanisms and fail-safe safety indicators so that operator exposure is effectively impossible.
In meeting provincial regulatory requirements, each system was surveyed by Health Physics for safety when initially commissioned.
Additional quarterly inspections are conducted by supervisory CEDT staff to ensure all safety mechanisms continue to function properly.
Non-ionizing electromagnetic radiation
McMaster University's non-ionizing radiation safety program is outlined in RMM 702.
Non-ionizing electromagnetic radiation is of insufficient energy to cause atomic or molecular damage directly, however, the heat generated by exposure to intense non-ionizing radiation can be sufficient to induce tissue damage.
The category includes visible and infrared light, as well as microwaves and radio-waves.
Most sources of electromagnetic radiation decay rapidly with distance from the source.
It is possible to shield electromagnetic radiation by surrounding the source with a grounded conductive shield or mesh, where any openings in the shield must be less than one quarter of the radiation wavelength.
Particular caution should be paid to microwave and radiofrequency generators common in plasma generation systems.
These sources can create fields with high power and specific directionality.
Shielding is critical, as the radiation can damage tissues.
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Sources:
1. McMaster University Risk Management Manual #700, October, 2005.
2. McMaster University Health Physics Radiation Safety Manual, October, 2005.
3. McMaster University Health Physics "X-ray Safety Training for X-ray Users," Course Manual, October, 2005.