Recent developments in the regulatory and legal arenas have placed increased emphasis on the issues involved in pregnancy and work with sources of radiation, an area that has always been difficult for employers. Fortunately for UCD and its employees, there is relatively little concern about actual radiation doses received in most cases of radiation workers in our biomedical research laboratories. This is because the vast majority of "radiation workers" at UCD have little potential exposure to ionizing radiation, if standard hygienic practices are followed to avoid self-contamination. However, because of the legal and health issues involved, and because of the great significance of the related emotional issues to individual workers, it is crucial that both workers and supervisors be well-informed. Furthermore, UCD is required, by the Colorado Department of Public Health and the Environment, Radiation Control Division (who licenses the UCD for use of radioactive materials), to document that all radiation workers have been given this information. For that reason, the material contained in this chapter is now required reading for all radiation workers at UCD, and for all Principal Investigators authorized for use of radioactive materials or other sources of radiation.

The following material is presented in a question-and-answer format to add interest. Additional questions should be directed to the UCD Radiation Safety Officer, Health and Safety Division, Box C-275, ext. 5-5890.

Q. Who is a radiation worker, and who is not?

A. A radiation worker is any person who works with, or is potentially exposed to, any source of ionizing radiation apart from natural back- ground radiation, during the course of his or her activities at UCD, and whose work conditions are therefore controlled to minimize such exposure. This includes all persons who work directly with radioactive materials, even in very small quantities. Some additional personnel, such as persons using dental x-ray machines, are also considered radiation workers.

Most, but not all radiation workers are required by UCD policy to wear personnel dosimeters (film or TLD [Thermoluminescent Dosimeter] badges) issued by HSD. (Workers who work only with soft beta emitters (H-3, C-l4, S- 35) are not required to wear dosimeters.) Being a radiation worker implies that one is informed about the health issues related to radiation and the type and extent of potential radiation doses involved in one's work, and that one accepts these matters as conditions of employment. All radiation workers who work directly with radioactive materials are required to complete the radiation safety certification modules and examinations administered by HSD.

A. This question is not nearly so foolish as it sounds! Due to legal precedent involving issues such as employment discrimination, the regulatory agencies with purview in this area have determined that a radiation worker is pregnant, for purposes of radiation safety regulations, only after she has declared her pregnancy in writing to her employer, along with the estimated date of conception. Until an employee makes said declaration, she is not considered pregnant, no matter how visibly apparent her condition may seem to others, including her supervisor. Furthermore, it is possible for a declared pregnant radiation worker to revoke her declaration of pregnancy, without regard to her actual condition. Supervisors must be sensitive to the fact that inquiry into an employee's pregnancy or fertility status, especially if they take on an intrusive or accusatory tone, may be legitimately protested by the employee as an invasion of privacy.

Workers are encouraged to declare their pregnancy as soon as it becomes known to them, and to inform the UCD Radiation Safety Officer in writing. Because so few workers at UCD have any potential exposure to significant levels of ionizing radiation, the pregnant worker and her supervisor can usually make decisions about work assignments without anticipating that she might, in any case, receive significant radiation doses in her work. But there are cases, discussed in more detail below, that warrant consideration of the radiation dose that may be received by the declared pregnant worker.

Q. Wait a minute! What are you calling a "significant" radiation dose?

A. All persons living in the Colorado area receive about 180 mrems per year, or fifteen millirems per month, of radiation dose to the whole body, from cosmic rays, from gamma rays given off by naturally-occurring radioactivity in soils, rocks, and building materials, and from other natural sources. In addition, all Colorado residents receive a dose to the lung epithelium, from the alpha particles given off by radon gas, primarily encountered in the home environment. This dose is typically equivalent to another 200 to 400 mrems of whole-body dose. Because each person's background dose varies with a number of lifestyle choices (e.g., place of residence, time spent in the mountains at higher elevations than Denver, time spent flying on jet aircraft, smoking habits, etc.), the individual background dose can easily vary by several tens of millirems per year or more. This provides a basis for one type of perspective on what levels of work-related dose might be considered significant, or even practical to control.

Another and more legally compelling perspective comes from the regulations. State and federal regulations now (as of 1/1/94) require that no employer may expose a declared pregnant worker to more than 500 millirems of dose to the fetus over the full term of gestation, which equates to about 55 millirems per month. For the sake of conservatism, no supervisor would want to place a declared pregnant worker in a situation in which the anticipated dose would exceed a fraction of this amount

By these criteria, anything more than ten millirems in a month, above background, should be considered potentially significant for a declared pregnant worker.

Q. What happens if a pregnant worker decides not to declare her pregnancy?

A. She would continue to be monitored as an adult worker. This means that the statutory Maximum Permissible Dose (MPD) that is applicable is 5 mrems (5,000 millirems) per year on the standard film badge, which is considered a "whole body" dosimeter. A non-declared pregnant worker would receive a letter from the Radiation Safety Officer, consistent with the As Low As Reasonably Achievable (ALARA) Program that is always in place for all radiation workers at UCD, if her whole-body dose in any calendar quarter (January through March, April through June, etc.) exceeds 125 millirems. (For exposure to penetrating radiations from external sources, we would normally assume fetal dose to be equal to whole body dose.)

When a pregnant worker does not declare her pregnancy, the fetal dose is not separately monitored, tracked, and reported, and the 500-millirem limit for the nine-month term of pregnancy is not applied to fetal dose. In terms of the typical situations that apply at UCD, the pregnant worker should be aware that, although she is unlikely to get a significant fetal dose in occupational situations that exist in the biomedical research laboratories, failure to declare her pregnancy means that the fetal dose will not be separately tracked and monitored, and her equivalent whole- body dose will not be scrutinized with as much rigor and timeliness, by the Radiation Safety Officer, as the fetal dose of a declared-pregnant worker. In the situations that exist at UCD, it is very unlikely that a female worker would be required to accept a new job assignment because she declared her pregnancy. Declaration of pregnancy is generally unlikely, for instance, to prevent an investigator from continuing her research. Female workers should consider the above implications carefully in deciding whether or not to declare their pregnancy.

A. Typically, almost nothing. Let's talk first about external dose, arising from sources outside the body, so we are not talking about a situation in which the worker has contaminated herself with radioactive material and somehow gotten the material inside her body. Rather, we are talking only about the exposure that a person gets from being in the vicinity of some source of penetrating radiations, that penetrate through the container in which the radioactive material is housed.

Beta particles, even the higher-energy ones from P-32, are not sufficiently penetrating to reach the fetus, even if they are not shielded. For that reason, soft beta emitters (H-3, C-14, S-35, Ca-43) are not a potential source of external exposure. With regard to P-32, it must be noted that, although the high-energy betas themselves cannot penetrate and deliver fetal dose, a small fraction of those betas do generate bremsstrahlung x-rays as the betas are absorbed, and the x-rays are much more penetrating than the betas. When P-32 is present in quantities on the order of tens of milliCuries or more, the exposure rate from bremsstrahlung x-rays, within a meter or two of the P-32, may be significant enough to be of concern, if a worker is spending significant periods of time in that area.

It is the radioisotopes that emit gamma rays and x-rays that are the principal concern in regard to external exposure. I-125 produces a dose rate of about 0.07 millirems per hour per milliCurie, at a distance of one meter, if it is totally unshielded.

Cr-51, another commonly-used gamma emitter, only produces one photon for every ten atomic disintegrations, so it only produces a dose rate of about 0.016 millirems per hour per milliCurie, at a distance of one meter, totally unshielded. A few milliCuries of I-125, or five to ten milliCuries of Cr-51, should not produce exposure rates of concern, if they are shielded with a small amount of lead. Most shipping containers for these radionuclides currently provide adequate shielding for this purpose.

I-131 is a more potent gamma emitter, producing a dose rate of about 0.22 millirems per hour per milliCurie, at a distance of one meter, totally unshielded. I-131 is also more difficult to shield. Thus, 1-131 requires substantially more consideration than I-125 and Cr-51. The Radiation Safety Officer should be consulted for more information about these and other gamma-emitting radionuclides, if they are present in quantities exceeding a few tens of microCuries.

Another important note is that pregnant workers who may be using the large animal irradiator in Room 0636 of the School of Medicine should consult the Radiation Safety Officer. This unit, with the source fully retracted into the shield, produces dose rates of less than 1 mrem per hour in the vicinity of the irradiator itself (inside the vault, where the cells or other objects to be irradiated are placed into position), and does not produce exposure rates measurably in excess of background in the console area. For these reasons, it is unlikely that a person using this unit, even several times per week could exceed one to two millirems of dose per month. However, the size and nature of this source, for which the vault is posted as a High Radiation Area, require particular care in its use.

Q. Is there any other way that a pregnant worker can be exposed to radiation?

A. There certainly is. In fact, given the type and quantities of radioactive materials in use at UCD, the most significant hazard is internal exposure to radioactive materials. This means getting the radioactive material itself inside your body. This can happen by accidental ingestion (e.g., by mouth-pipetting or by transferring contamination from your hands to food, etc.). It can also happen by skin absorption, if the contamination that you get on your skin is in a soluble form that can be absorbed across the skin into underlying tissues. And it can happen by inhalation, if you are working with radioactive material in volatile form, or if you disperse it into the air as an aerosol, and you are not working in a properly operating fume hood. Declared pregnant workers should not be performing radioiodination labeling experiments, if it can be avoided.

It should be strongly emphasized that, in general, for biomedical research uses, the most important protective factor in most cases is good radiological hygiene.

Q. What if a worker had already gotten some dose before she realized, and/or declared, her pregnancy?

A. The dose limit is a little more complicated to apply in this case, but is set forth explicitly in the regulations. The Radiation Safety Officer should be consulted. Again, there is little likelihood that the worker will have

received any dose of concern, if proper precautions that are appropriate for all workers are being followed, because of the limited types and quantities of radioactive materials that are in use at UCD.

Q. What happens to a baby that is exposed to radiation before birth?

A. At the dose levels that are possible in routine biomedical research work, there is no certainty that anything will happen. In fact, even at dose levels of hundreds of millirems of acute fetal dose (dose received all at once), there is only a very small probability of any adverse effect. The potential health effects of concern are divided into three broad categories: carcinogenesis, mutagenesis, and teratogenesis. Carcinogenesis includes the induction of early childhood cancers and leukemias due to radiation dose received in utero. Mutagenesis includes the creation of defects in the genetic material of the parents, prior to conception, or possibly the creation of defects in the genetic material of the fetus as it exists in utero, that would result in heritable genetic defects being passed on to succeeding generations. Teratogenesis includes the induction of developmental defects in utero, resulting in the child being born with developmental abnormalities (birth defects). Such defects could include mental retardation, in addition to structural or metabolic deficiencies. All of these issues, including numerical risk estimates and a reference list, are addressed in detail in Appendices A and B of the U.S. Nuclear Regulatory Commission’s Regulatory Guide 8.13. Most of this document is incorporated into this Study Manual. For a complete copy contact HSD. In addition, further discussion of some of this health risk information may be warranted, in light of new information that has emerged since the publication of Regulatory Guide 8 13. With respect to induction of cancer or leukemia in early childhood, due to in utero exposure, a more recent review cites a risk factor of 2 x10 ^-4 excess cancer deaths per rem [Hoffman], as opposed to the factor of 6 x 10^-6 per rem cited by the NRC publication. However, it should also be noted that the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiation Protection (ICRP) have estimated that in utero exposure leads to excess cancer risk later in life as an adult, with a risk coefficient two to three times that of exposure received as an adult [Meinhold]. This latter risk factor, for excess cancer deaths due to radiation dose received as an adult, is on the order of 2 x 10^-4 to 4 x 10^-4 per rem, depending on assumptions about dose rate factors [BEIR V]. With respect to induction of mental retardation, to which there is an apparent sensitivity in the period from about 8 to 15 weeks post concept-ion, it should be noted that there is substantial evidence for a threshold dose, below which this effect would not occur at all. This threshold has been estimated to be in the range of 10 to 20 rems. An alternative explanation for the existence of an apparent threshold derives from the view that this effect is at least predominantly a mass effect, also called a non-stochastic effect This is an effect that occurs with certainty at all dose levels, but has a severity proportional to the radiation dose. The NCRP and ICRP have taken a position in recent years that supports the incidence of severe mental retardation as a manifestation of an overall IQ shift, which is greatest at the highest doses (on the order of 100 rems) received by atomic bomb survivors that were irradiated in utero [Meinhold]. The coefficient for IQ shift has been estimated to be in the range of 0.21 to 0.29 IQ points per rem of fetal dose. With respect to the production of heritable genetic defects in the genome of a fetus in utero, or, for that matter, in the genome of an exposed adult, there is very little discussion of this effect in the NRC Regulatory Guide. That is because the effect of mutagenesis has never been demonstrated in human study populations, even those as heavily irradiated as the atomic bomb survivors. The effect theoretically exists, based on the radiobiology of animals, such as the famous early studies of Drosophila, but is presumably only probable enough to be observed, even in a fraction of an exposed population, at very high doses. The most recent data support a calculated doubling dose (doubling the natural rate of mutations) in excess of 100 rems (BEIRV). There is some difficulty in specifying the existence of the effect as well, given that many mutations, such as recessive ones, would not be observable in individuals of the first few generations of an exposed population, and the fact that exposed populations would not be genetically isolated as they propagate. Despite these complications, the overall genetic risk is not considered to be a limiting factor in this situation, and the dose limits for the fetus are based primarily on the other potential health effects discussed above [NCRP]

A. Probably not. Some concern was aroused a few years ago by a study in the UK, called the Gardner study or the Sellafield study. It demonstrated a statistically significant connection between a cluster of childhood leukemia cases and the occupational radiation exposure of the fathers prior to conception, which was on the order of several rems (several thousand millirems). This study has been seriously questioned as a valid indicator of paternal radiation dose as a cause of childhood leukemia, and this connection has not been supported by a recent Canadian study. The usual guidelines, including maintaining radiation doses As Low As Reasonably Achievable, should be sufficient to protect male workers with respect to paternity, as well as for their own health. With reasonable care and appropriate procedures, no worker at UCD should have to receive gonadal doses exceeding a few tens of mrems per month, and doses will typically be indistinguishable from background. This last statement is supported by many thousands of person-months' worth of monitoring reflected in the records maintained by HSD.

Q. Does a pregnant radiation worker need a special film badge?

A. Not absolutely, but it is recommended that declared pregnant workers take advantage of the fetal monitoring service provided by our film badge vendor, including the ordering of a separate fetal badge. A separate film badge for fetal monitoring will be supplied at minimal expense, along with special dosimetry reports. The standard whole-body film badge should be worn at waist level, on the front (anterior aspect) of the body. This provides a second valid estimate of fetal dose, so that two results are obtained for purposes of verification, The dosimeters should he exchanged promptly each month for the new films provided by HSD. The RSO can be consulted at any time (ext. 5-5890) to obtain the most recent dosimetric results.

Q. If a worker declares her pregnancy, and she and her supervisor agree that there is no prospect of her receiving any significant radiation dose in connection with her normal work, is there any reason to consider changing her work conditions or work assignment?

A. There may still be reason to consider changes. It should be borne in mind that a substantial fraction of all live births involve some defect. If the worker in question happens to be such a case, and especially if she was not comfortable with the radiation aspects of her work situation, the implications for all of the parties involved, worker, supervisor, and the UCD, are potentially problematic.

On the other hand, there may be equally valid reasons to consider not changing the work conditions and assignment. For instance, in some cases, it may set an untenable precedent to excuse a worker from her normal duties on account of pregnancy, if the case involves a small department that must accomplish a certain workload, and dosimetric experience, along with health physics analysis, indicates that workers in the category in question are not receiving significant radiation doses. There is also a valid philosophical objection to creating or reinforcing the impression that radiation work is harmful or dangerous, even when proper controls are in place, materials are being used safely, and there is no prospect of a workers’ receiving a measurable radiation dose.

Supervisors and/or workers are encouraged to request the Radiation Safety Officer to perform a health physics evaluation of a declared pregnant worker's assignments. If such an evaluation indicates that a given work assignment many be completed safely, and that no significant radiation dose is to be anticipated if standard precautions and hygienic practices are followed, the supervisor does have the right to require the declared pregnant worker to perform the assignment in question, if it is otherwise a normal part of her duties, and if the supervisor feels that the declared-pregnant worker’s performance of the assignment is necessary to the operation of the work unit.

In cases where then is no reason to expect the declared-pregnant radiation worker to receive a significant radiation dose, the Radiation Safety Officer has no regulatory or legal basis to require, or even recommend, a specific decision about work conditions and assignments. In such a case, the decision rests solely with the worker and supervisor, who should consider the above factors, as well as any others that they think are valid.

Additional questions should be directed to the UCD Radiation Safety Officer at ext. 5-5890

EFFECTS OF RISK FACTORS ON PREGNANCY OUTCOME

Effect No. Occurring Risk Factor Excess Occurrences from Natural Causes from Risk Factors

Back to Section 5