To the Editor: An Australian businessman travelled to the United States by air 1 week after receiving a second therapeutic dose of 8 mCi (300 MBq) iodine-131 for thyrotoxicosis due to Graves’ disease. He carried no medical documentation, but had with him carbimazole tablets, to be recommenced 1 week after the dose.

While awaiting passport clearance at Los Angeles, he noticed that an attendant from homeland security was monitoring the line of passengers with a hand-held device no larger than a mobile phone. He was approached and asked if he was a doctor, or if he was under medical treatment. He indicated that he had received radioiodine recently. The official appeared to be aware of the situation and moved him to the front of the line. He was asked whether he had a letter from his doctor or whether he had medication with him. No letter was to hand, but the medication was shown. He was escorted to collect his baggage and was taken aside for detailed questioning. His luggage and person were searched in detail and information entered into a database. The episode caused significant distress.

On two occasions during the next week, he re-entered the US from Canada, by which time he had a letter that documented his medical treatment. On each occasion he was detected by the surveillance system, and questioning and search procedures were repeated.

Current radiation detection devices in use at airports appear to have very high sensitivity.1 A recent detailed study that compared the sensitivity of various hand-held radiation detectors in recording various radionuclides,2 showed that therapeutic doses of I-131 could be detected for up to 95 days, F-18 FDG was detectable for 1 day, Tc-99m would trigger the alarm for 3 days, and Tl-201 or Ga-67 could be detected for up to 30 days.2 The authors of that study concluded:

Some devices are quoted as being able to detect 0.01 MBq of I-131 at 2 m —3 m,1 a level of activity that might still be present 3–4 months after treatment with 400 MBq (about 11 mCi) I-131, within the standard dose range for thyrotoxicosis. It is now a medical responsibility to make people who have received relevant radionuclides such as I-131, Tl-201 or Ga-67 aware of this travel hazard, to avoid unexpected apprehension in circumstances that cause delay and distress. Such patients should ensure that they carry appropriate medical documentation with them when they travel and should be aware that they may be interrogated and searched, even if they have documentation.

To our knowledge, no similar surveillance is currently used at Australian airports.