1. Working with Radioisotopes: Reducing the Risk
UW Radiation Safety Manual
Chapters 2, 3 and 4
Today we will continue discussing the biological effects of radiation, touch on radiation protection standards and then begin discussing the basic principles of radiation safety.

2. Radioisotopes as biological hazards
high energy beta emitters: both external and internal hazards
low energy beta and alpha emitters: internal hazards only
We mentioned that radioisotopes present different types of biological hazards. High energy beta emitters are both external and internal hazards, and low energy beta and alpha emitters are only internal hazards. What happens to the radioisotope if it somehow gets into the body? It is metabolized like non-radioactive isotopes. If it is not incorporated into an organ, the isotope remains in the body for only about 32 hours. Therefore, it poses only a slight hazard. If it is incorporated into an organ, it remains in the body for much longer.

3. Biological Half-life
T 1/2B: the time required for the body to reduce the amount of a chemical or substance to one-half its original amount
The biological half-life (T1/2B) is the time required for the body to reduce the amount of a chemical or substance to one-half its original amount.

4. Effective Half-life
At the same time, in the case of a radioisotope, the isotope is decaying according to its physical half-life
Biological and physical half-lives combined give an effective half-life which reflects the amount of time that isotope is damaging the body
These two half-lives combined give an effective half-life which reflects the amount of time that isotope is damaging the body. This ranges from about a week isotopes like Iodine-131 and Carbon-14 to nearly two years for nickel-63.
!!!Please note, this discussion concerns elemental radioisotopes. For compounds that have radioactive atoms incorporated, the effective half-life can be much longer.!!!!

5. Effective Half-life
These two half-lives combined give an effective half-life which reflects the amount of time that isotope is damaging the body. This ranges from about a week isotopes like Iodine-131 and Carbon-14 to nearly two years for nickel-63.
!!!Please note, this discussion concerns elemental radioisotopes. For compounds that have radioactive atoms incorporated, the effective half-life can be much longer.!!!!

6. Working with radioactivity
Risks?
Unclear
Some studies suggest low risk
To a large extent, it is unclear. Some studies suggest that the risk is low, for example, the National Cancer Institute found no increased risk of cancer in 107 US counties near 62 nuclear power plants. But, there have been some isolated pockets of increased cancer that may be due to radiation exposure.

7. The risks of low-level exposure
The knowledge is lacking
The knowledge about the risks of long-term LOW-LEVEL radiation exposure is lacking. The numbers we do have are a result of ACUTE Exposures:
For instance, studies have followed survivors of Hiroshima and Nagasaki. As of 1985, these survivors had had 5000 deaths due to cancer, with 250 being radiation-induced.

8. The linear, no-threshold model
Regulatory agencies use a linear, no threshold model to predict effects of radiation
For regulation purposes, agencies use a linear, no threshold model to predict effects of radiation. Thjs model:
1. Assumes no cellular repair
2. Is expected to overestimate number of cancers due to radiation exposure
There have been estimates of loss of life expectancy for radiation workers versus other occupations and risk factors:
Health risk Estimated loss in life expectancy
Smoking 20 cigs/day 6 years
Overweight (15%) 2 years
Avg. alcohol intake 1 year
Car accidents days
Home accidents 74 days
Natural disaster 7 days
Medical diag. Radiation 6 days
Avg. rad. Worker 15 days
Agriculture 60 days
Constructions days
Mining days
Manufacturing 40 days
3. Extrapolates in a linear fashion from data from high dose exposures.
4. Sets limits for all body parts for maximum possible doses per year.

9. Occupational risk factors
Health risk Estimated loss in life expectancy
Smoking 20 cigs/day 6 years
Overweight (15%) 2 years
Avg. alcohol intake 1 year
Car accidents days
Home accidents 74 days
Natural disaster 7 days
Medical diag. radiation 6 days
Avg. rad. worker 15 days
Agriculture days
Constructions days
Mining days
Manufacturing 40 days

10. Sources of radiation exposure
The average American receives a dose of 357 mrem per year.
82% of this is from natural exposure sources
Man-made: Major source is medical or dental
The average American receives a dose of 357 mrem per year. 82% of this is from natural sources.
Natural sources:
Cosmic radiation (exposure greater as altitude increases. Denver has twice
The exposure as sea level areas)
Terrestrial—elements in earth’s crust . Also housing materials
Radon—produced by uranium decay
Internal-from things we eat and drink
Man-made:
Major source is medical or dental

11. Basic principles of protection
TIME, DISTANCE, SHIELDING
1. TIME: The length of time a radiation worker is exposed to source
2. DISTANCE: Exposure decreases with square of distance from the source.
3. SHIELDING: Radiation releases its energy as it passes through matter. Shielding allows another material other than body tissue to absorb the dose. Different isotopes require different materials and thicknesses of shields.

12. Types of shielding
Different isotopes require different materials and thicknesses of shields
a. Alpha particles: Can be stopped by even a piece of paper. Stopped by dead layer of skin.
B. Beta particles: Smaller mass = faster velocity. High energy beta shielded by plastic, Lucite or aluminum. Do not use lead because as the beta passes through the lead, X-rays are emitted.

13. Safety Guidelines Always wear protective clothing Monitor frequently.
Remove gloves and wash hands when finished.
Always wear protective clothing (e.g., disposable gloves, lab coat, safety glasses) when handling radioactive materials; these protect skin and clothing from contamination and shield the skin from beta particle absorbed dose.
Beta particles do not penetrate far and so will deposit all energy in a very small area so will give that area a very high dose is concentrated isotope contaminates the skin. Wear labcoat and double glove)
Monitor frequently. Remove gloves and wash hands when finished. Leave lab coat in the lab when you leave.

14. Safety Guidelines
Do work in a fume hood if gas, vapor, dust or aerosols can occur during the procedure.
Do not eat, drink, etc
Do not mouth pipette
Do work in a fume hood if gas, vapor, dust or aerosols can occur during the procedure.
Do not eat, drink, or perform other hand-mouth procedures (e.g., licking stamps or labels, applying makeup,etc.) in any room or lab which has been posted Caution - Radioactive Materials.
Do not mouth pipette ,not even water. Bad practices, once started, may become habitual with the consequent risk of ingestion of radioactive materials or other toxic substance.

15. Safety Guidelines Lock and secure stock vials when not in use.
Do not store food or drink containers in the same location as radioactive materials.
Do not bring personal belongings into the radioactive work areas of the lab.
Lock and secure stock vials when not in use.
Do not store food or drink containers in the same location as radioactive materials. This particularly applies to refrigerators containing (or labeled as containing) radioactive materials; these refrigerators are off limits for lunch bags, milk cartons, and other food or drink containers.
Do not bring personal belongings into the radioactive work areas of the lab. Avoid wearing rings, watches, and similar items during work. Wearing shorts, sandals, or slippers is also not recommended.

16. Safety Guidelines Always wear dosimeter Bandage cuts
Watch for contamination of containers
If issued a radiation dosimeter (see Chapter 7), wear it/them when working with radiation sources.
Do not work with radioactive materials if you have an open cut or wound; contamination may enter thebody through a cut.
Assume containers labeled Caution - Radioactive Materials are also contaminated and wear disposable gloves when handling all such containers.

17. Safety Guidelines
Employ the three basic safety principles of time, distance and shielding.
Contain any spills
Employ the three basic safety principles of time, distance and shielding whenever you work with external hazards and employ good housekeeping techniques when using any radioactive material. When doing a new procedure, perform a "dry run" without radioactive materials to learn the procedure.
Do liquid radiation work on a non-porous tray which is capable of containing the entire volume of a liquid radioactive material in case it is spilled. Cover the work area with plastic-backed absorbent material.

18. Safety Guidelines Monitor!!
Be familiar with properties of radioisotopes in use
Immediately after use or work with radioactive materials, wash hands then monitor them thoroughly. Monitor hands and clothing for radioactive contamination during and after work; especially before leaving the lab. If you are contaminated or suspect you are contaminated, wash the contaminated area and re-monitor (cf. Chapter 6 and 7) as necessary; notify Safety of problems.
Monitor the rooms where radioactivity is used or stored, and pay special attention to all areas which may come in contact with potentially contaminated hands, e.g., phone, door knob, refrigerator handle.
Workers should be thoroughly familiar with the properties of the radionuclides they are using. If you are uncertain about the safety of a procedure or have any questions about radioactivity call Radiation Safety.