Patients with thyroid disorders treated with 131I represent radiation hazard to household contacts including caregivers and family members. Many studies reported that no radiation overexposure was reported if RSI were applied strictly with radiation exposure figures within the radiation exposure constraints [20,21,22]. Few studies are there dealing with radiation exposure to children and adolescents sharing the same home with the patient in the post-131I therapy period [23,24,25,26]. In the current study, we were concerned with external radiation exposure to this vulnerable group of children and adolescents. In our study, CRE to all children and adolescents were less than the 1 mSv constraint, and 75% of them had CRE below 50% of this constraint. No statistically significant difference in CRE of children between contacts of patients treated with 131I for toxic goiter and those treated for cancer thyroid.
It was reported by Barrington et al.  that about 90% of children, contacts to patients treated with 131I were within the 1-mSv dose limit. They concluded that hyperthyroid patients can be treated with 131I on an outpatient basis, if they were given appropriate radiation protection instructions; yet, they raise the point that a special concern should be given to children aged less than 3 years, as 6/17 of them had exceeded CRE of 1 mSv limit. In our study, we had only 6 children less than 3 years with CRE figures ranged from 0.079 to 0.571 mSv, with an overall 100% compliance for the constraint of 1 mSv.
On the other hand, Mathieu et al.  reported a median CRE of children who were household contacts of thyrotoxic patients treated with 131I was 0.13 mSv (18 outpatients received 200–600 MBq) with 88% received less than the constraint of 0.5 mSv compared to 100% of thyroid cancer patients’ relatives group (22 outpatients received 3700–7400 MBq). 131I retention in the thyroid gland in thyrotoxic patients was accused for this difference, suggesting the need of more extended and stringent restriction periods according to the degree of residual thyroid activity. In our study, only 23 of the contacts exceeded the limit of 0.5 mSv with CRE in the range from 0.5 to 0.934 mSv, which was still lower than the constraint of 1 mSv; out of these contacts, 11 were contacts of hyperthyroid patients. The compliance to 0.5 mSv constraint in our study was 77% and 80.8% for contacts of hyperthyroid patients and thyroid cancer patients, respectively. In the current study, there are comparable values for this compliance together with insignificant difference in CRE figures between contacts of those with toxic goiter and those with well-differentiated thyroid cancer despite the significantly higher doses of 131I given in the latter group. This is attributed to more 131I retention in the intact thyroid gland in those with toxic goiter compared to little tracer retention by the small postoperative residual thyroid tissue in patients with thyroid cancer. This difference in tracer retention appears to compensate for the significant difference in the dose given and accused for the comparable exposure figures of contacts of both groups.
Few studies reported radiation overexposure to children who are household contacts of 131I-treated patients. Molyvda-Athanasopoulou et al.  reported an outpatient who got 131I therapy (592 MBq) for her hyperthyroid state. They found that this patient had a 12-year-old daughter who received 7.79 mSv during the first 7 days post-therapy period. It was reported to be unexpected for a child in this age, who is able to understand and comply with given radiation safety precautions, to have such high radiation exposure figure. They suggested that in the presence of children in the house, it is better to leave the house for at least a week if possible, but if this cannot be done due to social reasons, giving 131I therapy with hospital admission should be considered . Also, although Cappelen et al.  reported exposure figures below the 1-mSv constraint, they reported an overexposure to a two-year-old child whose mother did not comply with the given radiation safety precautions. Besides, a recommendation was raised that patients who share the same bedrooms or bathrooms with family members or mothers who are going to be treated with 131I and has no one to look after her children in the post-therapy period should be treated on an inpatient basis by a study conducted on Omani patients . All previous studies advised appropriate radiation protection precautions to be given with particular consideration to instructions for children ≤ 12 years. The aforementioned studies support our recommendation of properly giving RSI by RSO to mothers in details. This should be done especially for the treated mothers, with special emphasis and more details about radiation safety precautions regarding their offsprings. Additionally, we have to be sure about their ability to comply with these instructions or at least confirming the presence of somebody else who can care for their child in the few days post-outpatient 131I therapy. Otherwise, if this is not feasible, we agree with other reports as regards the recommendation of giving low-dose 131I therapy on an inpatient basis to avoid radiation overexposure to children and adolescents.
Patients and contact factors such as age and gender together with patients’ educational level as well as the relation of the contact to the patient had no statistically significant correlation with CRE (p values > 0.05). This goes with what was previously reported by Kuo et al.  stating that no factor (e.g., age, sex, renal function, and others) had a significant association with radiation exposure to household family members unless they were in close contact with the patient for a long time. Also, our results are in agreement with what was stated by Martin et al.  who confirmed the absence of a significant correlation between household contacts radiation exposure and patient education level.
It was found that adolescents and children of mothers who attended direct RSI sessions given by the RSO had significantly lower CRE figures. This emphasizes the value of getting RSI education directly from qualified professionals. The attendance of these education sessions by both patients and contacts is recommended, being associated with a significant reduction in CRE figures and more importantly ensuring the ability to comply with these instructions and to apply them strictly in the proper way. These recommendations are in agreement with other reports emphasizing the value of RSI and their proper application [24, 30].