Is it safe to work with iodine-131 if you are pregnant? A risk assessment for nuclear medicine staff involved with cleaning and decontamination.
In the UK, Regulation 8(5) of the Ionising Radiation Regulations 1999 (In: Work with ionising radiation. London: HSE Books, 2000) requires employers to ensure that the dose to the foetus of a pregnant worker is unlikely to exceed 1 mSv. Risk assessments are required which are capable of predicting the total foetal dose. Work involving 131I is a particular problem. Foetal dose coefficients from the maternal intake of 131I for all stages of pregnancy have been published (Phipps AW, Smith TJ, Fell TP, Harrison JD. Doses to the embryo/fetus and neonate from intake of radionuclides by the mother. NRPB contract research report 397/2001. Didcot, Oxon.: National Radiological Protection Board (NRPB), 2001. Available on website www.hse.gov.uk/research/crr_pdf/2001/crr01397.pdf), and range from 0.08 microSv x kBq(-1) at conception to 55 microSv x kBq(-1) at week 35. This paper examines one aspect of work in a nuclear medicine department in which the source of 131I is uncontrolled to determine whether the risk assessment indicates that restrictions should apply to a pregnant member of staff. Following in-patient treatment with 131I, rooms are checked and decontaminated before being decontrolled. Cleaning staff were monitored immediately after the cleaning process with hand-held detectors and by whole-body monitoring. Total body contamination ranged up to 3.2 kBq; after a change of clothing, the maximum remaining activity was 0.68 kBq. Acquired contamination correlated with the total activity administered to the patient. Hand-held monitoring rarely detected contamination. Whole-body monitoring indicated that the levels of contamination encountered could lead to a dose limit for the foetus being exceeded. These levels are very difficult to detect with hand-held monitoring. The conclusion to be drawn is that pregnant staff should be excluded from situations in which accidents could arise, or where the source of 131I is uncontrolled or unpredictable.
Barber
R W
RW
Department of Nuclear Medicine, Addenbrooke's Hospital, Cambridge, UK.
Parkin
A
A
Goldstone
K E
KE
D000016:Abnormalities, Radiation-Induced / Q000517:prevention & control*; D000488:Allied Health Personnel; D003666:Decontamination; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000032:analysis* / Q000627:therapeutic use; D018811:Maternal Exposure / Q000009:adverse effects* / Q000517:prevention & control / Q000592:standards; D008431:Maternal-Fetal Exchange; D008954:Models, Biological; D009684:Nuclear Medicine Department, Hospital; D016273:Occupational Exposure / Q000032:analysis*; D011247:Pregnancy; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods* / Q000592:standards; D011874:Radiometry / Q000379:methods* / Q000592:standards; D019275:Radiopharmaceuticals / Q000032:analysis / Q000627:therapeutic use; D018570:Risk Assessment / Q000379:methods*; D014915:Whole-Body Counting
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals