This report considers the consequences of occupational exposures leading to intakes of radionuclides by women who are, or may become, pregnant. Estimates are given of potential doses to offspring following intakes of a selected range of naturally occurring and artificial radionuclides that might arise for different contamination scenarios in the workplace. The radionuclides covered are of interest from both routine operations and accidental releases.
Doses can arise both from the transfer of radionuclides to the embryo and foetus, and from activity in the mother’s tissues. The relative contributions of these two sources vary widely depending on the emissions of each radionuclide. Doses are also calculated for the lifetime of the newborn child from activity present at birth.
The total dose coefficient for the offspring (the sum of the in utero and postnatal doses) calculated in this report is compared to the dose coefficients recommended by ICRP for workers. Of particular interest are cases where the offspring dose is greater than the worker dose since these are the cases where the normal standards for protection of workers may not afford sufficient protection to the offspring. Isotopes of hydrogen, carbon, phosphorus, sulphur, iodine and the alkaline earth elements fall into this category. Isotopes of calcium and phosphorus, show the greatest differences between offspring and worker doses with the ratio of the two being over 15 for ingestion of calcium-45 or phosphorus-32. In utero doses for the actinides such as plutonium-239 are at most only a few per cent of the corresponding worker dose.
In some cases intakes by the mother that occurred well before pregnancy can lead to significant doses to the foetus; this is of particular relevance to the advance planning of protection for female workers. A general implication of this report is that intakes of some radionuclides may need to be restricted to lower levels than those that would lead to a dose to the worker of 1mSv. This report thus provides the basis for the guidance given by HSC in the 1999 Regulations.
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