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Lessons Learnt from a 131I Contamination Case in Production of Radiopharmaceuticals

This paper discusses a case of heavy skin contamination with radioactive iodine in a radiopharmaceutical production facility, highlighting the challenges faced and lessons learnt.

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Lessons Learnt from a 131I Contamination Case in Production of Radiopharmaceuticals

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  1. Lessons learnt from a 131I contamination case in production of radiopharmaceuticals M. Muikku, J. Huikari, H. Korpela, C. Lindholm, W. Paile, T. Parviainen International Conference on Global Emergency Preparedness and Response IAEA, Vienna 19.-23.10.2015

  2. Content • Description of the 131I contaminationincident • Monitoring • Doseassessment • Challenges and lessonslearnt

  3. Description of the 131I contamination incident In a Finnishcompanymanufacturingradiopharmaceuticals, a workerwasheavilycontaminated in 2013. • The workerwascleaning adeviceusedfor production of 131I therapycapsules (approximateactivity of onecapsule 3.7 GBq) • Sheworetwopairs of protectinggloves, frequentlychanging the outerpair. The outerpairwas of latex and the inner of nitrile. • Whenchangingglovesshenoticed a rupture in the rightinnerglovebutnot in the outerglove. Shechangedbothpairs, butdidnotcheck for contamination. • 3 – 4 h later, when she left the production area, routine monitoring revealed heavy contamination of the back of the right hand and also slight contamination of the left hand. The skin was intact, no wound was noticed.

  4. Description (continue) • The radiation safety officer was notified and decontamination was performed immediately on site with 0,1 M KI and 70% ethanol. • Decontamination removed approximately half of the original contamination. Repeated washing had no further effect. • The worker was told to wear gloves at home to protect home surroundings, and to change gloves and wash hands frequently. • Stable iodine was not given. • Next morning (about 22 hours after the incident) the level of contamination on the right hand was still high. Activity was also noticed in the thyroid with a NaI-scintillation detector. • At this point STUK was notified and the worker arrived at STUK in the afternoon for more detailed measurements

  5. Monitoring • At STUK the surface contamination on the back of the employee’s hand was estimated using: • a NaI scintillation detector (Mini-Monitor 900, probe 42A) • an Atomtex RKG-AT1320A thyroid monitor and • STUK’s mobile whole body counter • Dose rate meter A thyroid monitor Atomtex RGK AT 1320 (Minsk, Belarus)

  6. Monitoring (continue) STUK's mobile whole body counter with two HPGe-detectors

  7. Monitoring (continue) • The Atomtex RKG-AT1320A thyroid monitor, STUK’s whole body counter and a dose rate meter were also used to determine the 131I activity in the thyroid. • Monitoring of the right hand and thyroid were repeated four, eleven and fifteen days after the incident. • The worker gave spot urine samples on the second and fourth day and collected 24 hour urine samples two and nine days after the incident. • A blood sample for biological dosimetry was taken 15 days after the incident.

  8. Monitoring (continue) • An autoradiography of the back of the right hand was performed on day four to better estimate the contaminated area. The hand was held for 20 minutes against a Kodak PQ phosphor screen removed from the casette. A lead weight was kept in the palm to ensure immobilization. A rough estimate of the contaminated area: 10 cm2

  9. Dose assessment • A thyroid dose of 430 mGy was estimated from the thyroid measurement data using IMBA professional pro software (Birchall et. al. RadiatProtDosim 105 (2003) 421). • The 131I activity in the thyroid was highest in day four. Health Phys 107 (2014) 351

  10. Dose assessment (continue) • The skin dose was estimated at 33 Gy, assuming that the contaminated skin area was 10 cm2. The dose is calculated at a depth of 0.07 mm (approximately the depth of the basal cell layer of the epidermis). • One day after the incident slight reddening of the right hand, but also some of the left hand. Vigorous, repeated washing? Irritation from gloves and sweat? • On day 11, slight dryness and desquamation of the right hand. • On day 15, intact skin and no desquamation left. • After 3 months: no sign of damage. • The estimated superficial skin dose is close to the estimated threshold (35 Gy) for severe skin damage for the slightly more energetic beta emitter 170Tm (Hopewell et al. Radiat Res 133 (1993) 303). • The dose estimate may be somewhat conservative.

  11. Dose assessment (continue) • The result of the chromosomal aberration analyses is indicative of a small, partial exposure, a finding that is in line with the described incident. • The estimation of the effective dose is not relevant when there is a risk for serious tissue reactions. For dose recording purposes an effective dose of 17 mSv was estimated from the thyroid exposure. Work as a classified radiation worker was prohibited in 2013 on the basis of the high local skin dose. • The case was classified as INEX 2, because the annual dose limit of radiation workers was exceeded.

  12. Challenges and lessons learnt Heavy skin contamination with radioactive iodine can lead to significant exposure - not only of the skin but also of the thyroid. • One day after the incident 17% of the initial activity was left in the skin, and after four days, 1%. • The content in the thyroid was highest after 4 days. • Assuming that 30% of the iodine that entered the circulation was taken up by the thyroid, the iodine uptake into the blood was about 9% of the initial contamination (12 MBq) on the back of the hand. Administration of stable iodine would have prevented any further absorption into the thyroid and reduced the thyroid dose substantially– even if given one day after the incident. To allow a timely reaction to the incident authorities should have been notified already when the skin contamination was noticed.

  13. Challenges and lessons learnt (continue) • Contamination monitoring is important if anything anomalous is noticed during the routine operations. Personnel should also be able to correctly interpret the readings (often in cps) of their hand monitor. • As no special monitors were available to quantify the activity on the back of the hand improvised monitoring set-ups were used. The autoradiography should have been performed earlier in order to get a more detailed picture. • The dose estimation was not straightforward as the activity in both the skin and the thyroid changed over the time. The dose reconstruction based on cytogenetic analysis is also very challenging in cases of internal contamination, as lymphocytes are exposed heterogeneously with a variable dose rate.

  14. STUK made an inspection on site and gave instructions to evaluate risks, to use thicker gloves and to keep iodine tablets at hand. Thank you for your attention!

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