Regulatory Guide 8.13
| ML13350A220 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1975 |
| From: | NRC/OSD |
| To: | |
| References | |
| RG-8.013 | |
| Download: ML13350A220 (4) | |
...! ..... Q ....M 7r'March 1975U.S. NUCLEAR REGULATORY
COMMISSION
RE Q U LAT Y GWU DEOFFICE OF STANDARDS
DEVELOPMENT
REGULATORY
GUIDE 8.13INSTRUCTION
CONCERNING
PRENATAL
RADIATION
EXPOSURE
A. INTRODUCTION
Section 19.12 of 10 CFR Part 19 states that allindividuals working in or frequenting any portion of arestricted area must be instructed in the health pro-tection problcms associated with exposure to radioactive materials or radiation.
This guide describes the instruc-tion that should be provided concerning biological risksto embryos or fetuses resulting from prenatal exposure.
B. DISCUSSION
Since the Law of Bergonie and Tribondeau waspublished in 19061 it has been known that the sensitiv- ity of cells to radiation damage is related to theirreproductive activity and inversely related to theirdegree of differentiation.
It follows that children couldW .,," be expected to be more radiosensitive than adults,fetuses more radiosensitive than children, and embryoseven more radiosensitive.
This principle has long been a factor in thedevelopment of radiation exposure standards.
Section20.104 of 10 CFR Part 20 places different limits onminors than on adult workers.
Specifically, it limitsanyone under the age of 18 to exposures not exceeding
10% of the limits for adult workers.A special situation arises when an occupationally
, exposed woman is pregnant.
Exposure of the abdomen: of such a worker to penetrating radiation from eitherexternal or internal sources would also involve exposureof the embtyo or fetus. Because a number of studieshave indicated that the embryo or fetus, is more sensitive dthn an adult, particularly during the first three monthsCorjttes Rendus des Seances de I'Aeademie des Sciences.
VoL143, pp. 983-985,
1906.after conception, when a womaii may not be aware thatshe is pregnant, the National Council on Radiation Protection and Measurements (NCRP) recommended inits Report No. 39 that special precautions be taken tolimit exposure when an occupationally expo'ed womancould be pregnant.
C. REGULATORY
POSITIONInstruction to workers performed under § 19.12should be given prior to assignment to work in arestricted area. In providing instruction about healthprotection problems associated with radiation exposure, female workers and those who may supervise or workwith them should be given specific instruction aboutprenatal exposure risks to the developing embryo andfetus.The instruction should ensure that the employees understand:
1. That the NCRP has recommended holdingprenatal occupational exposure to 0.5 rem or less duringthe entire period of gestation;
and2. The reasons for this recommendation.
The instruction should include the information provided in the Appendix to this guide. It should bepresented to the employee, her supervisors, and herco-workers both orally and in written form. Each personshould be given an opportunity to ask questions, andeach person should be asked to acknowledge in writingthat the instruction has been received.
D. IMPLEMENTATION
The purpose of this section is to provide informa-don to licensees regarding the use of this guid
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I
Except In those cases in which the licensee choosesto propose an alternative method for complying with theportion of the Commission's regulations previously specified, the methods described herein should be usedafter September
1, 1975, to instruct female employees working in or frequenting any portion of a restricted area, and -those who may supervise or work with suchemployees, concerning the health protection problemsassociated with prenatal radiation exposure.
APPENDIX
TO REGULATORY
GUIDE 8.13POSSIBLE
HEALTH RISKS TO CHILDREN
OF WOMENWHO ARE EXPOSED TO RADIATION
DURING PREGNANCY
.Some recent studies have shown that the risk ofleukemia and other cancers in children increases if themother Is exposed to a significant amount of radiation during pregnancy.
According to a report by theNational Academy of Sciences, the incidence ofleukemia among children under 10 years of age in theUnited States could rise from 3.7 cases in 10,000children to 5.6 cases in 10,000 children if the childrenwere exposed to I rem of radiation before birth (a"rem" is a measure of radiation).
The Academy has alsoestimated that an equal number of other types ofcancers could result from this level of radiation.
tuthough other scientific studies have shown a muchsmaller effect from radiation, the Nuclear Regulatory Commission wants women employees of its licensees tobe aware of any possible risk so that the women can takesteps they think appropriate to protect their offspring.
As an employee of a Nuclear Regulatory Commis-Sion licensee, you may be exposed to more radiation than the general public. However, the Nuclear Regula-tory Commission has established a basic exposure limitfor all occupationally exposed adults of 1.25 reins percalendar quarter, or 5 reins per year. No clinical evidenceof harm would be expected in an adult working withinthese levels for a lifetime.
Because the risks of undesir-able effects may be greater for young p)eople, personsunder 18.years of age are permitted to be exposed toonly 10 percent of the adu!. occupational limits. (Thislower limit is also applied to members of the generalpublic.)The scientific organization called the NationalCouncil on Radiation Protection and Measurements hasrecommended that because unborn babies may be moresensitive to radiation than adults, their radiation dose asa result of occupational exposure of the mother shouldnot exceed 0.5 rem. Other scientific groups, including the International Commission on Radiation Protection, have also stressed the need to keep radiation doses tounborn children as low as practicable.
All Nuclear Regulatory Cornnii&sion li'ensees arenow required*
to inform all Individuals who work in a*By Title 10. Part 19 of the Code of Federai Regulations.
restricted area of the health protection problems asso-ciated with radiation exposure.
This instruction would inmany cases include information on the possible risks tounborn babies. The regulations also state* thatlicensees should keep radiation exposures as low aspracticable.
According to the National Council onRadiation Protection and Measurements, particular efforts should be made to keep the radiation exposure ofan embryo or fetus at the very lowest practicable levelduring the entire period of pregnancy.
Thus it is the responsibility of your employer totake all practicable steps to reduce your radiation exposure.
Then it is your responsibility to decidewhether the exposure you are receiving is sufficiently low to protect your unborn child. The advice of youremployer's health physicist or radiation protection officer should be obtained to determine whether radia-tion levels in your working areas are high enough that ababy could receive 0.5 rem or more before birth. If so,the alternatives that you might want to consider are:(a) If you are now pregnant or expect to be soon,you could decide not to accept or continue assignments in these areas.(b) You could reduce your exposure, wherepossible, by decreasing the amount of time you spend inthe radiation area, increasing your distance from theradiation source, and using shielding.
(c) If you do become pregnant, you could ask youremployer to reassign you to areas involving less exposureto radiation.
If this is not possible, you might considerleaving your job. If you decide to take such steps, do sowithout delay. The unborn child is most sensitive toradiation during the first three months of your preg.nancy.(d) You could delay having children until you areno longer working in an area where the radiation dose toyour unborn baby could exceed 0.5 rem."In Title 10, Part 20.8.13-2
You may also, of course, choose to:(e) Continue working in the higher radiation areas,but with full awareness that you are doing so at somesmall increased risk for your unborn child.The following facts should be noted to help you make adecision:
1. The first three months of pregnancy are themost important, so you should make your decisionquickly.2. At the present occupational exposure limit, theactual risk to the unborn baby is small, but expertsdisagree on the exact amount of risk.3. There is no need to be concerned about sterility or loss of your ability to bear children.
The radiation dose required to produce such effects is more than 100times larger than the Nuclear Regulatory Commission's dose limits for adults.4. Even if you work in an area where you receiveonly 0.5 rem per three-month period, in nine monthsyou could receive 1.5 reins, which exceeds the full-term limit suggested by the NCRP. Therefore, if you d&cide torestrict your unborn baby's exposure as recommended by the NCRP, be aware that the 0.5 rem limit applies to* the full nine-month pregnancy.The remainder of this document contains a briefexplanation of radiation and its effects on humans. Asyou will see, some radiation is present everywhere andthe levels of radiation most employees of NuclearRegulatory Commission licensees receive are not muchlarger than these natural levels. Because the radiation levels in the facility where you will be working arerequired by law to be kept quite low, there is notconsidered to be a significant health risk to individual adult employees.
0.072 rem per year. The average dose from one chestX-ray is 0.045 rem.Radiation can also be received from natural sourcessuch as rock or brick structures, front consumer pro-ducts such as television and glow-in-the-dark watches,and from air travel. The possible annual dose fromworking 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> a day near a granite wall at the RedcapStand in Grand Central Station, New York City, is 0.2rem, and the average annual dose in the United Statesfrom TV, consumer products, and air travel is 0.0026rem.Radiation, like many things, can be harmful.
A largedose to the whole body (such as 600 reins in one day)would probably cause death in about 30 days, but suchlarge doses result only from rare accidents.
Control ofexposure to radiation is based on the assumption thatany exposure, no matter how small, involves some risk.The occupational exposure limits are set so low, how-ever, that medical evidence gathered over the past 50years indicates no clinically observable injuries to indi-viduals due to radiation exposures when the established radiation limits are not exceeded.
This was true even forexposures received under the early occupational ex-posure limits, which were many times higher than thepresent limits. Thus the risk to individuals at theoccupational exposure levels is considered to be verylow. However, it is impossible to say that the risk is zero.To decrease the risk still further, licensees are expectedto keep actual exposures as far below the limits aspracticable.
The current exposure limits for people working withradiation have been developed and carefully reviewed bynationally and internationally recognized groups ofscientists.
It must be remembered, however, that theselimits are for adults. Special consideration is appropriate when the person being exposed is, or may be, anexpectant mother, because the exposure of an unbornchild may also be involved.
Prenatal Irradiation The prediction that an unborn child would be moresensitive to radiation than an adult is supported byobservations for relatively large doses. Large dosesdelivered before birth alter both physical development and behavior in experimentally exposed animals.
Areport of the National Academy of Sciences states thatshort-term doses in the range of 10 to 20 reins causesubtle changes In the nerve cells of unborn and infantrats. The report also states, however, that no radiation- induced changes in development have been demon-strated to result In experimental animals from doses upto about I rem per day extended over a large part of theperiod before birth.The National Academy of Sciences also noted thatdoses of 25 to 50 reins to a pregnant human may causeDiscussion of Radiation The amount of radiation a person receives is calledthe "dose" and is measured in "reins."
The averageperon in the United States gets a dose of one rem fromnatural sources every 12 years. The dose from naturalradiation is higher in some states, such as Colorado, Wyoming, and South Dakota, primarily because ofcosmic. radiation.
There the average person gets one remevery 8 years.Natural background radiation levels are also muchhigher in certain local areas. A dose of one rem may bereceived in some areas on the beach at Guarapari, Brazil,in only about 9 days, and some people in Kerala, India,get a dose of one rem every 5 months.Many people receive additional radiation formedical reasons.
The annual radiation dose averaged overthe United States population from diagnostic X.rays is'C8.13-3 growth disturbances in her offspring.
Such doses sub.stantially exceed. of course, the maximum permissible occupational exposure limits.Concern about prenatal exposure (i.e., exposure of achild while in its mother's uterus) at the permissible occupational levels is primarily based on the possibility that cancer (especially leukemia)
may develop during thefirst 10 years of the child's life. Several studies have beenperformed to evaluate this risk. One study involved thefollowup of 77.000 children exposed to radiation beforebirth (because of diagnostic abdominal X-rays made formedical purposes during their mother's pregnancy).
Another stud)y involved the followup of 20.000 suchchildren.
In addition,
1292 children who receivedprenatal exposure during the bombing of Hiroshima andNagasaki were studied.
Although contradictory resultshave been obtained, most of the evidence sugests arelationship between prenatal exposure and an increased risk of childhood cancer.SummaryOccupational exposures to radiation arc being keptlow. flowever, qualified scientists have recommended that the radiation dose to a pregn,,.nt woman should notexceed 0.5 rem because of possible risks to her unbornchild. Since this 0.5 rem is lower than the dose generally permitted to adult workers, women may want to takespecial actions to avoid receiving higher exposures, justas they might stop smoking during pregnancy or mightclimb stairs more carefully to reduce possible risks totheir unborn children.
Bibliography Donald G. Pizzarello and Richard L. Witcofski, Basic Radiation Biology, Philadelphia:
Lea andFebizer.
1967.2. National Academy of Sciences
-National ResearchCouncil, The Effccts on Populations of Exposure toLow Levels of Ioni:ing Radiation, Washington, D.C., November
1972.3. National Council on Radiation Protection andMeasurements.
Basic Radiation Protection Criteria, NCRP Report No. 39, Washington, D.C., January15, 1971.4. United Nations.
Ionizing Radiation:
Levels andEffects,
2 vol., Reports of the United NationsScientific Committee on the Effects of AtomicRadiation, Report No. A/8725, United Nations.New York, 1972.5. US. Atomic Energy Commission, Division ofTechnical Information, Understanding the AtomSeries:Atoms, Nature and AlanThe Genetic Effects of Radiation The Natural Radiation Environment Your Body and Radiation UNITED STATESNUCLEAR REGULATORY
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