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The State of Washington Department of Health (DOH), Radiation Protection Division
has established dose limits which are based on recommendations from national
and international commissions.
The table below lists the limits set by DOH:
|
Organ
|
DOH Limit
(mrem/year)
(Sv/year)
|
University of Washington investigation level
(mrem)
|
Comments |
|
Total Effective Dose Equivalent (TEDE)
Whole Body
|
5000
0.05
|
500/month
1000/quarter
|
Includes dose from both internal and external sources. The Whole
Body limit applies to exposure of the torso and head when the radiation
is penetrating enough to irradiate tissues at a depth of 1 cm where
the deeper blood-forming tissues are located.
|
|
Lens Dose Equivalent Lens of the Eye
|
15,000
0.15
|
1,500/month
3,000/quarter
|
The Lens of the Eye limit applies to exposure of the eye to radiation
penetrating enough to irradiate the lens, at a depth of 0.3 cm
|
|
Extremities
Shallow Dose Equivalent
|
50,000
0.5
|
5,000/month
10,000/quarter
|
The extremities include the arm or leg below the elbow or knee.
The Extremities limit applies to exposure of the extremities when the radiation
is penetrating enough to irradiate tissues at a depth of 1 cm
|
|
Skin
Shallow Dose Equivalent
|
50,000
0.5
|
5,000/month
10,000/quarter
|
The Skin limit applies to dose deposited in the skin when the radiation
is penetrating enough to irradiate tissues at a depth of 0.007 cm
|
|
Embryo/Fetus
|
500 (for the entire pregnancy)
0.0005
|
50
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Applies only when a Declaration of Pregnancy has been submitted
|
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Occupational exposure of a minor
|
10% of the limits above
|
Occupational exposure of a minor is not permitted at the UW
|
Applies to anyone under 18 years of age |
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Member of the general public
|
100
0.0001
|
50
|
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The University has established investigational levels at doses considerably
less than the dose limits. When a worker accumulates during any part of
a year a dose at or above the investigational level, the Radiation Safety Office (RSO)
will investigate
to determine causes of the dose and to recommend practices to minimize
radiation exposure in the future.
Since the current model of radiation-induced cancer risk assumes that
there is a risk no matter how low the radiation dose, it makes good sense
to minimize radiation exposure. In fact, the University is required by
NRC regulation to keep doses As Low As Reasonably Achievable (ALARA).
This means that the University must work to keep doses as far below the
dose limits as can reasonably be achieved.
To keep doses ALARA, the University has established investigational
dose levels and will investigate any dose exceeding these levels in
an effort to address causes of unnecessary radiation exposure.
In addition there are a variety of practical steps that you can take
while working with sealed sources to minimize your radiation exposure. These steps
will be described in detail in the Using Sealed Sources Safely
Module.
This section provides a general overview of the Declared Pregnant Worker
Program. More detailed information about the program is available
in Section
6 of the University of Washington Radiation Safety Manual.
The Washington State DOH's Fetal Dose Regulations apply only to a woman who
has voluntarily informed her employer, in writing, of her pregnancy and the estimated
date of conception. The dose to the fetus resulting from occupational
exposure of a declared pregnant woman may not exceed 500 mrem for the entire
pregnancy.
Submitting a Declaration of Pregnancy
Any radiation worker who is pregnant or believes that she may be pregnant
should contact the RSO. All inquiries will be kept in confidence. Radiation Safety will
take the following steps:
-
Provide an opportunity to submit a Declaration of Pregnancy. (A Declaration
of Pregnancy form may be obtained from Radiation Safety.)
-
Provide information concerning risk of fetal radiation exposure.
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Evaluate the worker’s dose history and exposure potential.
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Make recommendations for reducing radiation exposure.
-
Monitor the worker’s radiation dose with regard to worker and fetal dose
limits.
For the type of radiation work performed at the University of Washington, it is
rarely necessary to recommend reassignment or changes to job duties.
If a written declaration of pregnancy is not submitted to Radiation Safety, then
the worker’s dose continues to be controlled under the normal dose limits
for radiation workers.
Section
6 of the University of Washington Radiation Safety Manual provides
detailed information about the University of Washington's Declared Pregnant
Worker Program
This is the end of the Dose Limit Module, which is the fifth of the
seven Sealed Source Radiation Basics training modules. The next module
is the Dosimetry Module.
Dosimetry
(Module 6)
Back
to the Sealed Source Training Introduction Page
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