Analysis of radiation doses received by the public from 131I treatment of thyrotoxic outpatients.

Radiation doses to the family and general public from 131I therapy of outpatients were assessed for comparison with the 1990 International Commission on Radiation Protection (ICRP) dose limits. Doses to family members of such patients, measured by previous workers, were converted to show that on average 5.6 +/- 3.7 microSv MBq-1 is received by the spouse and 1.5 +/- 0.87 microSv MBq-1 by other family members. It was deduced that the average dose to the spouse (D microSv MBq-1) when couples sleep apart for T days after administration is given by: D = 2.528 + 3.072e-0.11T if an effective half-life, T(eff), of 6.35 days is used. The cumulative effect of repeated treatments should be considered and in view of ALARA it is recommended that couples sleep apart for at least 14 days after each administration, even if this is below limits permitted by authorities. The dose to a pregnant colleague or family member other than the wife should be below 2 mSv if the total administered activity is not more than 600 MBq. If the wife is pregnant, couples should sleep apart for at least 30 days after administration.