Reconsidering Current Decorporation Strategies after Incorporation of Radionuclides.

In the case of a nuclear accident or a terrorist attack by a "dirty bomb," there is a risk of external and internal contamination with radionuclides in addition to external irradiation. Internal irradiation as a consequence of radionuclide incorporation is associated with a higher risk of stochastic radiation effects (e.g., tumors). Decorporation treatment will enhance the elimination of radionuclides and reduce the committed effective dose as a metric of stochastic health effects. Although treatment efficacy is better when started early, beginning the therapy without knowing the committed effective dose may unnecessarily expose the patient to the side effects of the medication. The question is: Delay the therapy to wait for the results of internal dosimetry or start the therapy promptly on spec? To prove insight into this question, a selective review of the literature was conducted. The importance of the initiation time of treatment in the efficacy of decorporation treatment can be explained with pharmacokinetic laws and first order processes determining the disposition of xenobiotics in the organism. Nevertheless, there is no internationally accepted standard on when to start a decorporation therapy (exception: iodide). The "precautionary approach," emphasizing the importance of the committed effective dose for the indication of treatment, is competing with the "urgent approach" advocating the administration of medication "a priori" within several hours. A review of the literature actually indicates that the most important drugs used for decorporation are well tolerated with few adverse effects. In consideration of the higher efficacy and the low side-effects of a short-term treatment, initiating decorporation therapy as soon as possible after internal contamination, even before the committed effective dose has been assessed, appears to be a reasonable approach. The decision of continuation or discontinuation of the therapy should be taken after internal dosimetry is completed on the basis of the committed effective dose.

The MCART Consortium animal models series.

The single, overarching goal of the National Institute of Allergy and Infectious Diseases (NIAID)-sponsored Consortium, Medical Countermeasures Against Radiological Threats (MCART), is the development of medical countermeasures (MCM) to treat the key sequelae of the acute radiation syndrome (ARS) and the delayed effects of acute radiation exposure (DEARE). In addition, a parallel goal is to evaluate the toxicity and efficacy of decorporating agents that will reduce the whole-body burden of internalized radionuclides. MCM must be developed within the criteria of the U.S. Food and Drug Administration's (FDA) "animal rule" (AR) and the subsequent Guidance document for animal models that addresses essential elements to demonstrate efficacy under the animal rule; .The FDA AR underscores the requisite design and conduct of validated animal models as paramount in defining the regulatory pathway to licensure of MCM to treat personnel exposed to potentially lethal doses of radiation that define the major sequelae of the ARS and DEARE.

Murder by radiation poisoning: implications for public health.

On November 23, 2006, former Russian military intelligence officer Alexander Litvinenko died in a London hospital. Authorities determined he was deliberately poisoned with the radionuclide Polonium-210 (210Po). Police subsequently discovered that those involved in this crime had--apparently inadvertently--spread 210Po over many locations in London. The United Kingdom Health Protection Agency (HPA) contacted many persons who might have been exposed to 210Po and provided voluntary urine testing. Some of those identified as potentially exposed were U.S. citizens, whom the HPA requested that the Centers for Disease Control and Prevention (CDC) assist in contacting. CDC also provided health care professionals and state and local public health officials with guidance as to how they might respond should a Litvinenko-like incident occur in the U.S. This guidance has resulted in the identification of a number of lessons that can be useful to public health and medical authorities in planning for radiological incidents. Eight such lessons are discussed in this article.

Dosimetric calculations for uranium miners for epidemiological studies.

Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners.

Development of a database: DACTARI for a radiotoxic element ranking methodology.

Dosimetric impact studies aim at evaluating potential radiological effects of chronic or acute releases from nuclear facilities. A methodology for ranking radionuclides (RN) in terms of their health-related impact on the human population was first developed at CEA with specific criteria for each RN that could be applied to a variety of situations. It is based, in particular, on applying physico-chemical criteria to the complete RN inventory (present in the release or in the source term) and on applying norms related to radiation protection and chemical toxicology. The initial step consisted in identifying and collecting data necessary to apply the methodology, with reference to a previous database of long-lived radionuclides (LLRN, with half-lives ranging from 30 to 10(14) y) containing 95 radionuclides. The initial results have allowed us to identify missing data and revealed the need to complete the study for both toxic and radiotoxic aspects. This led us to the next step, developing a specific database, DAtabase for Chemical Toxicity and Radiotoxicity Assessment of RadIonuclides (DACTARI), to collect data on chemical toxicity and radiotoxicity, including acute or chronic toxicity, the chemical form of the compounds, the contamination route (ingestion, inhalation), lethal doses, target organs, intestinal and maternal-foetal transfer, drinking water guidelines and the mutagenic and carcinogenic properties.

Optimal designs for radiation retention with poisson correlated response.

In this paper we describe a non-linear model with correlated observations which accounts for the elimination rate of radiation in the lung of individuals who have been exposed to an accidental intake at some time. The response is then modelled as a conditional Poisson distribution. When the leak is moderate or the size of the particles is large a theoretical justification of this assumption is given and D-optimal designs are computed.

Health effects of airborne effluents released from the nuclear cycle.

Current trends in regulations governing radioactive release from the nuclear cycle and their relationship with population dose and population health damage evaluation are discussed. It is shown that, at least in some cases, current methods may not grant a correct population-dose evaluation. A procedure to better evaluate population doses from gaseous effluents is outlined. It leads to a very simple first approximation expression which is independent of the dispersion area. Two examples, 85Kr and 222Rn, are worked out in order to give first-order evaluations of the population-dose commitment and the related risk. Strong discrepancies between the results and current evaluations are found and discussed.