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You may be monitored for external or internal exposure, depending on the nature and source of the radiation you work with.
External exposure monitoring: External exposure is monitored with a device that absorbs radiation over a period of time. The device, called a dosimeter, is usually a badge or ring worn by the radiation worker. Dosimeters are periodically analyzed by Environment, Health & Safety (EH&S) and the data is used to calculate the worker's radiation exposure.
The dosimetry program manager reviews all dosimetry data and investigates any unusual exposures. EH&S reports the exposure data to the principal investigator. The report should be posted in the lab or otherwise made available to affected employees.
You need dosimetry if using any of the following:
- Greater than 1 mCi per experiment of a gamma or high-energy beta emitter
- Radiation-producing machines
If you work with only low-energy beta emitters, such as H-3, C-14, S-35, or P-33, you do not need dosimetry. If you operate a radiation-producing machine remotely, you may not need dosimetry.
Read about accessing and using dosimetry services:
Internal exposure monitoring: Other methods of determining exposure must be used when radioactive material is inhaled, ingested, or absorbed into the body.
A bioassay is a means of determining internal exposure through analysis of body fluids (in vitro) or direct measurement (in vivo). An example of an in vitro bioassay is a urinalysis. An example of an in vivo bioassay is a thyroid scan, a procedure in which the amount of radiation present is determined by holding a detector directly to the thyroid gland.
A baseline bioassay should be completed prior to performing experiments that require internal exposure monitoring according to the criteria below.
You need bioassay services if you're using any of the following:
- H-3 – Have your urine assayed every 2 weeks if more than 100 mCi of a volatile form of H-3 is used per month. EH&S will report positive analytical results to you as soon as results are available.
- Volatile iodine – Participate in the thyroid monitoring program if you use more than 10 mCi of volatile iodine per month. Monitoring frequency depends on the specific isotope of iodine:
- I-123 – At least 6 hours after, but within 2 days of a procedure.
- I-125 – At least 6 hours after, but within 30 days of a procedure.
- I-131 – At least 6 hours after, but within 5 days of a procedure.
- Performing multiple iodinations – A single bioassay is acceptable, as long as the time from the first iodination to the time of the bioassay doesn't exceed the limits listed above.
Employees who want a bioassay even though they're not required to, or because they suspect an uptake during a large spill, should contact EH&S Radiation Safety, (858) 534-6138.
How to get a bioassay: Bioassays are performed at the EH&S Services Lab. An appointment isn't necessary.
- Location: University Center Building 301-B
- When: 1–4:30 p.m., weekdays
If you need to come by at another time, call (858) 534-6418 to confirm a technician will be available.
Need an expert? Contact EH&S Radiation Safety, (858) 534-6138.
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