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General Public

1. What are the radiation risks to the public?

The public can be exposed to radiation from a radionuclide therapy patient as :

  • external radiation emitted from the patient, when in close contact (such as on public transport),
  • internal contamination from radioactive body fluids,
  • exposure through environmental pathways including sewage, discharges to waterways, or cremation of bodies.

In the case of the public, the normal dose limit of 1 mSv/year applies. Exposure of the public from radionuclide therapy is often caused from the external exposure, with internal contamination and environmental exposures contributing little, if any exposure. Specific discharge guidelines often provide the necessary information for a specific radionuclide and therapy.

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2. The patient has to use public transport regularly. What precautions should he take?

If travel times sitting next to a person administered with radiopharmaceutical are less than a few hours, radionuclide therapy patients rarely present a hazard, except for iodine-131 therapy when doses over 1000 MBq are administered.

For example, take the case of a patient treated with 600 MBq of iodine-131 for hyperthyroidism. One hour of travel daily on public transport in the first week after therapy, and nine hours per day in the second week, next to the same person, will result in an effective dose of <1 mSv-1.

For family members, the suggested travel time using public transport with hyperthyroid treatment patients is seven hours per day for the first week and 24 hours per day for the second week, to restrict the effective dose constraint of 5 mSv per episode - in other words, travel restrictions are often not necessary.

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3. Will the radioactivity from the patient harm the environment?

The main radionuclide discharged into the environment following radionuclide therapy is radioiodine (iodine-131). Due to the half-life of 8 days, iodine-131 may be detected in small amounts in the general environment after medical use. However, because of the high degree of dilution in a planned facility and dispersion when mixed with normal waste discharges, and the long period of time required for this activity to be returned to the ecosystem, the environmental impact may be minimal and often not even detectable.

Some countries require short-term storage of hospital waste (usually urine only) containing radionuclides from hospitalized therapy patients until the activity has reached a particular level; however, the ICRP does not specifically require this.

For radionuclides used in bone pain palliation, it is suggested in this guideline that where the therapy is given to an outpatient, the patient should empty the bladder at least once before leaving the hospital.

If the social system and infrastructure in a country increases the probability of higher exposure from discharged patients, it may be necessary to hospitalize the patient (if an outpatient therapy), or extend the normal hospitalization time.

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4. The patient is undergoing regular haemodialysis. Is this a risk?

There have been reports of significant contamination of dialysis machines. In cases where there may be slight contamination from iodine-131 of disposable items such as lines and waste bags, these may simply be allowed to decay a few half lives by storing them in a shielded and secure location. Otherwise, haemodialysis will not require additional precautions.

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5. How is the radioactive waste from the patient disposed of, and does it pose a risk?

The predominant issue is radioactive excreta - urine and faeces. The specific therapy discharge guidelines will recommend that excreted radioactivity levels be low enough such that the public dose limits would not be exceeded. In addition, the ICRP does not recommend that urine from therapy patients be stored - a procedure which has minimal benefit, and can even lead to higher exposures due to the additional and unnecessary handling of the urine. The IAEA Safety Report 63 also accepts this advice. It is safer and simpler to simply discharge the urine into the sewer system. The inherent shielding, dilution, and eventual decay will reduce the activity to minimal levels.

Other wastes such as dressings will usually end up in landfill or incinerators. Again, by following recommended specific therapy discharge guidelines, any released activity will be extremely low and negligible.

Solid waste from the patient's stay in hospital is a different matter, and is normally incinerated at high temperature along with other biological waste (which does not pose a contamination problem). It may also be held for a period of time so that the radioactive decay reduces the activity to an acceptable level. The relatively short half lives of therapeutic radionuclides make this a manageable problem.

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