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|
|
External
Monitoring
|
| External
occupational exposures from certain radionuclides and/or types
of radiation are primarily monitored with the use of personnel
dosimetry. The need for dosimetry is based on the nature and
frequency of usage, among other factors. Dosimetry is not
required for all uses of radiation and radioactive materials
at NIH. |
| Dosimetry
Eligibility |
| All
users of radiation and radioactive materials at NIH are required
to be evaluated for dosimetry. To complete the registration/training
process, all users must submit a completed Dosimetry Registration
Form. The individual's Authorized User must sign each dosimetry
registration form.
The back
of each dosimetry registration form contains a radionuclide
usage worksheet, which should be properly completed for an
accurate evaluation. A new worksheet should be submitted to
DRS whenever an individual's usage pattern changes!
Dosimetry
is NOT required for use of the following radionuclides:
H-3, C-14, S-35 Ca-45, P-33, I-125, 1-29
|
|
Dosimetry
MAY be required for use of the following radionuclides:
Na-22,
Na24, P-32, Fe-59, Cu-64, Ga-67, Ga-68, Se-75, Sr-89, Sr-90,
Mo-99, Tc-99m, I-131
|
| Other
areas where the use of radiation and radioactive material require
a dosimetry evaluation by DRS: |
| Patient
care |
Animal
use |
Nuclear
Medicine / PET |
| X-ray
machines |
Fluoroscopy |
Linear
Accelerators |
|
| Dosimetry
Storage and Maintenance |
| Dosimetry
should be worn properly and at all times when working with or
around radiation and radioactive materials.
When not
in use, dosimetry should be stored away from (or shielded
from) sources of radiation.
Dosimetry
should not be left in closed cars (due to sun or heat stress),
and should not be subjected to wet environments or chemicals.
Dosimetry
is used to monitor occupational radiation exposure only, so
it should not be worn outside of work, taken home, or otherwise
removed from the facility.
Dosimetry
is not intended to monitor radiation exposure from non-occupational
medical procedures.
|
| Interpretation
of Dosimetry Results |
| Dosimetry
results are received from the dosimetry contractor and reviewed
by DRS on a monthly basis for most monitored individuals.
DRS may
conduct an investigation of elevated exposures, based on predetermined
action levels and the nature of
the work performed during the period in question.
Exposure
investigations are not cause for alarm, as they are most often
conducted for exposures that are well within regulatory limits.
Investigations help determine the cause of an elevated exposure,
identify corrective actions, and ensure that future radiation
exposures are kept ALARA.
|
Internal
Monitoring |
| Internal
monitoring activities are conducted to assess the potential
intake (ingestion, inhalation, or absorption) of radioactive
material into the body. Bioassays (direct measurement of radioactive
material in the body) and personnel air sampling are the accepted
methods of internal monitoring at NIH. Internal monitoring requirements
depend on a number of factors including the experimental procedure,
activity used, and the chemical form (volatility) of the compound
in question. |
| Thyroid
Bioassay |
| Thyroid
bioassays are used to assess the intake of radionuclide compounds
that tend to concentrate in the thyroid gland (e.g., radioiodines).
As such, thyroid bioassays are sometimes required after the
use of volatile I-125 and I-131.
A baseline
thyroid bioassay is required prior to handling or observing
work with volatile radioiodine for the first time.
Thyroid
bioassays are a requirement of radiation safety protocols
that involve the use of potentially volatile radionuclides.
Depending on the activity and frequency or usage, a protocol
user may be required to undergo thyroid bioassay on a regular
basis.
Thyroid
bioassays may also be requested by DRS after spills, personnel
contamination, or other abnormal occurrences.
Thyroid
bioassays are conducted in Building 21, and may be scheduled
through the DRS Technical Services Section (6-4803).
|
| Urine
Bioassay |
| Urine
bioassays are used to assess the intake of radionuclides that
don't exhibit uptake within a particular organ. These compounds
are typically cleared from the blood via the kidneys, and can
be measured in the urine for a finite period following the intake.
A baseline
urine bioassay is required prior to participation in most
radiation safety protocol activities. If urine bioassay is
required by the protocol, a second urine bioassay will be
requested after the initial experiment.
Urine
bioassays may also be requested by DRS after spills, personnel
contamination, or other abnormal occurrences.
Urine
bioassay kits are available from the DRS Technical Services
Section (6-4803).
|
| Personnel
Air Monitoring |
| Along
with bioassay, personnel air monitoring is a requirement of
radiation safety protocols that involve the use of potentially
volatile radionuclides.
A personnel
air monitoring (breathing zone) apparatus is typically installed
by DRS, after which the research staff must collect air samples
during each experiment involving volatile radionuclides.
Based
on air monitoring results, DRS may request a bioassay or initiate
an intake investigation.
|
| Limits
and Action Levels |
| Occupational
radiation exposures are subject to regulatory limits, based
on the type of radiation or radioactive material involved. However,
the NIH Radiation Safety Program works to maintain compliance
with regulatory limits and minimize occupational exposures through
an ALARA Program. |
| Regulatory
Limits |
| |
NRC
|
OSHA
|
|
Whole
Body
|
5
rem/year
|
1.25
rem/quarter
|
|
Lens
of Eye
|
15
rem/year
|
1.25
rem/quarter
|
|
Skin
|
50
rem/year
|
7.5
rem/quarter
|
|
Extremities
|
50
rem/year
|
18.75
rem/quarter
|
|
Embryo/fetus
|
500
mrem/gestation
|
N/A
|
|
Minor
|
10%
of adult
|
10%
of adult<5(N-18) rem lifetime
|
|
General
Public
|
100
mrem/year2 mrem/hour
|
N/A
|
|
| Action
Guidelines |
| To
ensure compliance with regulatory limits, investigations are
performed when an occupational exposure exceeds pre-established
trigger levels: |
| |
NRC
|
OSHA
|
| Level
I |
10%
|
10%
|
| Level
II |
30%
|
30%
|
| Level
III |
N/A
|
50%
|
|
| Investigations
may be formal or informal, depending on the circumstances of
the exposure in question.
DRS will
determine when an investigation is warranted, based on the
external and/or internal monitoring results available for
a given individual.
|
NIH Policy on Breast-feeding Radiation Workers |
|
A breast-feeding radiation worker is capable of transmitting radioactive material to her child if she receives an internal uptake herself.
Not all radioactive material is a concern to breast-feeding women; the potential for uptake and subsequent transmission to a child via breast milk is greatest for volatile forms of radioiodine, and some potentially volatile forms of H-3, S-35, Br 76, and At-211.
A breast-feeding woman may choose to declare her breast-feeding status to the Division of Radiation Safety, similar to the “Declaration of Pregnancy” policy, above. The declaration form may be obtained from her Area Health Physicist.
A declared breast-feeding radiation worker will have her potential for internal uptake assessed and precautions agreed upon so that the child’s dose will be ALARA, below the general public dose limit of 100 millirem per year.
The declared breast-feeding worker may rescind her breast-feeding declaration at her discretion.
|
Fetal Exposure Monitoring – Declared Pregnancy Policy |
| The
NIH Fetal Protection Program has been established to minimize
occupational exposures to the embryo/fetus of a woman who has
formally declared her pregnancy to DRS. |
| Dose
Limit |
| Participation
in the Fetal Protection Program establishes a special dose limit
for the embryo/fetus of a declared pregnant woman (DPW).
The special
dose limit (500 mrem) applies to the entire gestation period
(nine months).
This limit
includes both internal and external doses received due to
occupation exposure to radiation and radioactive material.
|
| Declaration |
| Participation
in the Fetal Protection Program is entirely voluntary, and is
established through a formal declaration of pregnancy to DRS.
Declaration
of pregnancy is completely confidential. However, a DPW must
notify her Authorized User or supervisor, who is then responsible
for enforcing any radiation safety restrictions or precautions.
Declaration
of pregnancy may be made at any time during the pregnancy.
However, it is recommended that a declaration be made as soon
as possible to allow timely assessment of occupational exposure
risk.
To participate
in the Fetal Protection Program, a Declaration
of Pregnancy form may be submitted in confidence to
DRS. Mailing instructions are included on the form.
Medical
documentation of pregnancy is not required unless modification
of work assignment is necessary. If necessary, confirmation
of pregnancy may be obtained free of charge from the NIH Occupational
Medical Service
(OMS).
If a woman
chooses not to declare her pregnancy, DRS will not take steps
to evaluate or limit the dose to the embryo/fetus. However,
the pregnant woman will still be subject to the standard regulatory
limitsfor occupational radiation exposure, and will
be required to maintain her dose as low as reasonably achievable
(ALARA).
|
| Consultation |
| Following
written declaration of pregnancy, a health physicist will meet
with the DPW and her Authorized User (or supervisor) to: |
- review
information on the bioeffects of ionizing radiation
- assess
the woman's exposure potential
- discuss
any restrictions and/or precautions that may be necessary
- establish
an appropriate exposure monitoring program
|
| The
special dose limit is not expected to affect the scope of work
for the majority of women at NIH. Restrictions are only necessary
if there is a realistic potential for the embryo/fetus to receive
a dose in excess of 500 mrem during the pregnancy. |
| Regulatory
Guidance |
| For
more information on radiation health effects and prenatal radiation
exposure, feel free to consult the following sources:
NRC
Regulatory Guide 8.13, Instruction Concerning Prenatal
Radiation Exposure
NRC Regulatory Guide 8.29,
Instruction Concerning Risks from Occupational Radiation
Exposure
Copies
are available by calling the Radiation Safety Training Office
at 301-496-2255.
|
| Monitoring
Records |
| All
results of exposure monitoring are maintained electronically
or on file at DRS, and are available to individuals upon written
request. |
| Instructions
for Requesting Records |
| Submit
a written request to the Chief, Technical Services Branch,
DRS (Building 21).
Include
your name, social security number, and dates of employment.
All requests
for monitoring records are confidential. Therefore, all written
requests must be signed by the requesting individual. |
| ALARA |
| The
NIH Radiation Safety Program has been designed to ensure that
occupational doses and doses to members of the general public
are As Low As Reasonably Achievable (ALARA), and not just in
compliance with regulatory dose limits. |
ALARA
Principles |
- A concept
to reduce unnecessary radiation exposure in the workplace
- Applies
even if the maximum permissible dose is not exceeded
- A regulatory
requirement [10CFR20.1003, 10CFR20.1101(b), and 10CFR35.20]
- A requirement
of the NRC Type A Broad Scope license granted to NIH
|
Methods
of ALARA Compliance at NIH |
- Administrative
Controls
- Engineering
Measures
- Surveillance
- Enforcement
- Training
|
