adults. Studies of atomic bomb survivors exposed to acute radiation doses exceeding 20 rads (0.2 Gy) during pregnancy show that children born after receiving these doses have a higher risk of mental retardation. Other studies suggest that an association exists between exposure to diagnostic x-rays before birth and carcinogenic effects in childhood and in adult life. Scientists are uncertain about the magnitude of the risk. Some studies show the embryo/fetus to be more sensitive to radiation-induced cancer than adults, but other studies donot. In recognition of the possibility of increased radiation sensitivity, and because dose to the embryo/fetus is involuntary on the part of the embryo/ fetus, a more restrictive dose limit has been established for the embryo/fetus of a declared pregnant radiation worker. See Regulatory Guide 8.13, "Instruction Concerning Prenatal Radiation Exposure" for women (Refs. 1 and 4). These doses are far greater than the NRCs occupational dose limits for workers. Although acute doses can affect fertility by reducing sperm count or suppressing ovulation, they do not have any direct effect on one's ability to function sexually. No evidence exists to suggest that exposures within in the NRC's occupational limits have any effect on the ability to function sexually. If an occupationally exposed woman declares her pregnancy in writing, she is subject to the more restrictive dose limits for the embryo/fetus during the remainder of the pregnancy. The dose limit of 500 mrems (5 mSv) for the total gestation period applies to the embryo/fetus and is controlled by restricting the exposure to the declared pregnant woman. Restricting the woman's occupational exposure, if she declares her pregnancy, raises questions about individual privacy rights, equal employment opportunities, and the possible loss of income. Because of these concerns, the declaration of pregnancy by a female radiation worker is voluntary. Also, the declaration of pregnancy can be with­ drawn for any reason, for example, if the woman believes that her benefits from receiving the occupational exposure would outweigh the risk to her embryo/fetus from the radiation exposure.

########## Can a worker become sterile or impotent from normal occupational radiation exposure?

No. Temporary or permanent sterility cannot be caused by radiation at the levels allowed under NRC's occupational limits. There is a threshold below which these effects do not occur. Acute doses on the order of 10 rems (0.1 Sv) to the testes can result in a measurable but temporary reduction in sperm count. Temporary sterility (suppression of ovulation) has been observed in women who have received acute doses of 150 rads (1.5 Gy). The estimated threshold (acute) radiation dose for induction of permanent sterility is about 200 rads (2 Gy) for men and about 350 rads (3.5 Gy) for women (Refs. 1 and 4). These doses are far greater than the NRC's occupational dose limits for workers.

What are the NRC occupational dose limits? For adults, an annual limit that does not exceed: adults, an annual limit that does not exceed:

- • rems (0.05 Sv) for the total effective dose equivalent (TEDE), which is the sum of the deep dose equivalent • rems (0.05 Sv) for the total effective dose equivalent (TEDE), which is the sum of the deep dose equivalent (DOE) from external exposure to the whole body and the committed effective dose equivalent (CEDE) from intakes of radioactive material.
- • rems (0.5 Sv) for the total organ dose equivalent (TODE), which is the sum of the DOE from external • rems (0.5 Sv) for the total organ dose equivalent (TODE), which is the sum of the DOE from external exposure to the whole body and the com­ mitted dose equivalent (CDE) from intakes of radioactive material to any individual organ or tis­ sue, other than the lens of the eye.
- • rems (0.15 Sv) for the lens dose equivalent (LDE), which is the external dose to the lens of the eye. • rems (0.15 Sv) for the lens dose equivalent (LDE), which is the external dose to the lens of the eye.
- • rems (0.5 Sv) for the shallow dose equivalent (SDE), which is the external dose to the skin or to any • rems (0.5 Sv) for the shallow dose equivalent (SDE), which is the external dose to the skin or to any extremity.

For minor workers, the annual occupational dose limits are 10 percent of the dose limits for adult workers. For protection of the embryo/fetus of a declared pregnant woman, the dose limit is O.S rem (S mSv) during the entire pregnancy. The occupational dose limit for adult workers of 5 rems (0.05 Sv) TEDE is based on consideration of the potential for delayed biological effects. The 5-rem (0.05 Sv) limit, together with application of the concept of keeping occupational doses ALARA, provides a level of risk of delayed effects considered acceptable by the NRC. The limits for individual organs are below the dose levels at which early biological effects are observed in the individual organs.