Age-specific Biokinetic Models Research Articles

Risk assessment of uranium in water sources near coal mines and in human organs of Shahdol District, Madhya Pradesh, using biokinetic modelling.

This study concentrated on determining the levels of uranium present in drinking water samples obtained from various locations throughout the Shahdol district in Madhya Pradesh, India. In this assessment a LED fluorimeter Quantalase (LF-2a) was utilized. Uranium, being a radioactive substance, can be hazardous to health when consumed in significant quantities over extended durations. The study found that the average uranium concentration was 167.91µg/L. 82% of samples exceeded recommended limits, emphasizing the essential aspect of this study. The study utilizes the age-specific biokinetic model developed by the International Commission on Radiological Protection to examine uranium distribution across various organs. Using dosimetric model, the study provides a comprehensive health risk analysis by assessing the chemical toxicity and the radiation dosages received by particular organs. Longitudinal studies on uranium distribution across different organs and tissues showed that the kidneys, liver, non-exchangeable bone volume, and soft tissues are the primary locations where uranium accumulates.

Absorbed dose coefficients for pediatric differentiated thyroid cancer patients undergoing radioiodine therapy

The escalating incidence of differentiated thyroid cancer (DTC) in pediatric patients and the resultant growing use of radioactive iodine (RAI) reinforce the need to evaluate radiation exposure to normal tissues and radiation-induced health risks in pediatric patients undergoing RAI therapy. In the current study, we calculated absorbed dose coefficients (i.e. absorbed dose per unit activity administered, mGy MBq−1) specific for pediatric patients with localized DTC undergoing RAI therapy following total thyroidectomy for use in epidemiological studies. We first modified previously-published biokinetic models for adult thyroid cancer patients to achieve a reasonable agreement with iodine biokinetics observed in pediatric patients or design principles addressed in the International Commission on Radiological Protection (ICRP) reference age-specific biokinetic models. We then combined the biokinetic models in conjunction with S values derived from ICRP reference pediatric voxel phantoms. The absorbed dose coefficients for pediatric patients were overall greater than those for adults with a ratio (pediatric/adult) up to 11.6 and rapidly decreased with increasing age. The sensitivity analysis showed that the renal clearance rate and S values may have the greatest impact on the absorbed dose coefficients with the rank correlation coefficients ranging from −0.53 to −0.82 (negative correlations) and from 0.51 to 0.80 (positive correlations), respectively. The results of the current study may be utilized in clinical or epidemiological studies to estimate organ-specific radiation absorbed doses and radiation-associated health risks among pediatric thyroid cancer patients.

131I dose coefficients for a reference population using age-specific models

Age-specific dose coefficients are required to assess internal exposure to the general public. This study utilizes reference age-specific biokinetic models of iodine to estimate the total number of nuclear disintegrations ã(r S,τ) occurring in source regions (r S) during the commitment time (τ). Age-specific S values are estimated for 35 target regions due to 131I present in 22 r S using data from 10 paediatric reference computational phantoms (representing five ages for both sexes) published recently by the International Commission of Radiation Protection (ICRP). Monte Carlo transport simulations are performed in FLUKA code. The estimated ã(r S,τ) and S values are then used to compute the committed tissue equivalent dose HT(τ) for 27 radiosensitive tissues and dose coefficients e(τ) for all five ages due to inhalation and ingestion of 131I. The derived ã(r S,τ) values in the thyroid source are observed to increase with age due to the increased retention of iodine in the thyroid. S values are found to decrease with age, mainly due to an increase in target masses. Generally, HT(τ) values are observed to decrease with age, indicating the predominant behaviour of S values over ã(r S,τ). On average, ingestion dose coefficients are 63% higher than for inhalation in all ages. The maximum contribution to dose coefficients is from the thyroid, accounting for 96% in the case of newborns and 98%–99% for all other ages. Furthermore, the estimated e(τ) values for the reference population are observed to be lower than previously published reference values from the ICRP. The estimated S, HT(τ) and e(τ) values can be used to improve estimations of internal doses to organs/whole body for members of the public in cases of 131I exposure. The estimated dose coefficients can also be interpolated for other ages to accurately evaluate the doses received by the general public during 131I therapy or during a radiological emergency.

Age-Specific Thyroid Internal Dose Estimation for Koreans

Background: The International Commission on Radiological Protection is preparing to provide reference dose coefficients for environmental radioiodine intake based on newly developed age-specific biokinetic models. However, the biokinetics of iodine has been reported to be strongly dependent on the dietary intake of stable iodine; for example, the thyroidal uptake of iodine may be substantially lower in iodine-rich regions than in iodine-deficient regions. Therefore, this study attempted to establish a system of age-specific thyroid dose estimation for South Koreans, whose daily iodine intakes are significantly higher than that of the world population.Materials and Methods: Korean age-specific biokinetic parameters and thyroid masses were derived based on the previously developed Korean adult model and the Korean anatomical reference data for adults, respectively. This study complied with the principles used in the development of age-specific biokinetic models for world population and used the ratios of baseline values for each age group relative to the value for adults to derive age-specific values.Results and Discussion: Biokinetic model predictions based on the Korean age-specific parameters showed significant differences in iodine behaviors in the body compared to those predicted using the model for the world population. In particular, the Korean age-specific thyroid dose coefficients for 129I and 131I were considerably lower than those calculated for the world population (25%–76% of the values for the world population).Conclusion: These differences stress the need for Korean-specific internal dose assessments for infants and children, which can be achieved by using the data calculated in this study.

A systematic study of uranium retention in human organs and quantification of radiological and chemical doses from uranium ingestion

The Industrial revolution introduced umpteen radionuclides in the environment and their long-term exposure from ingestion and inhalation is a potential threat to the human race. In numerous developing countries, uranium and other radionuclide concentrations are higher than their recommended limits and cause adverse health effects to inhabitants. The present study depicts the uranium concentration in water samples of Nawanshahr and Rupnagar districts of Punjab (India). The uranium concentration in the studied region ranged from 13.23 μg l−1 to 38.61 μg l−1, and some samples reported to be have higher concentration than their recommended limits. An attempt has been made to quantify the uranium retention in different organs using ICRP’s age-specific biokinetic model with a specific update of urine, faeces, and hairs. The dosimetric models were used to estimate the radiological doses for particular organs and chemical toxicity for overall health risk assessment. Time dependence studies of uranium in distinct organs and tissues claimed that the kidney, liver, non-exchangeable bone volume and soft tissues are the vital target organs for uranium depository.

An age-specific biokinetic model for iodine

This paper reviews age-specific biokinetic data for iodine in humans and extends to pre-adult ages the baseline parameter values of the author’s previously published model for systemic iodine in adult humans. Compared with the ICRP’s current age-specific model for iodine introduced in Publication 56 (, pp 45–48), the present model provides a more detailed description of the behaviour of iodine in the human body; predicts moderately higher doses to the thyroid for short-lived isotopes of iodine; predicts similar doses to the thyroid for isotopes with half-time greater than a few hours; and, for most iodine isotopes, predicts substantially higher doses to salivary glands, stomach wall, liver, and kidneys.

Annals of the ICRP ICRP PUBLICATION 95 Doses to Infants from Ingestion of Radionuclides in Mothers’ Milk

In the present report, ICRP provides information on radiation doses to the infant due to intakes of radionuclides in maternal milk. As in Publication 88 (ICRP, 2001) on doses to the embryo and fetus following intakes of radionuclides by the mother, intakes by female members of the public and female workers are addressed. Acute and chronic intakes are considered at various times before and during pregnancy as well as during the period of breastfeeding. Dose coefficients per unit intake by the mother (Sv/Bq) are given for the selected radionuclides of the same 31 elements for which age-specific biokinetic models were given in Publications 56, 67, 69, and 71 (ICRP, 1989, 1993, 1995a,b). For these elements, doses were calculated for the most radiologically significant natural or artificial radionuclides that might be released into the environment due to various human activities. Dose coefficients are also given in this report for radionuclides of an additional four elements: sodium, magnesium,phosphorus, and potassium. Relevant human and animal data on elemental and radionuclide transfer to milk are reviewed. The biokinetic models for adults given in earlier ICRP publications are adapted to include transfer to milk. Model predictions of fractional transfer of ingested or inhaled activity to milk are discussed in the report, and the corresponding dose coefficients for the infant are compared with dose coefficients for in utero exposure, as given in Publication 88 (ICRP, 2001). Illustrative information is also given on doses to the female breast from radionuclides in breastmilk, and external doses received by the child from radionuclides retained in the tissues of the mother. For the additional elements considered in this report, but not in Publication 88 (ICRP,2001), information is also given on doses to the embryo and fetus following maternal intakes of radioisotopes during or before pregnancy. A CD-ROM is to be issued giving data that will supplement the information given in this report. In addition to the dose coefficients given here, committed equivalent doses to the various organs and tissues of the offspring will be given. Dose coefficients will also be given for inhalation of a range of aerosol sizes for the selected radionuclides of the elements covered by this report.

Doses to the Embryo and Fetus from Intakes of Radionuclides by the Mother: ICRP Publication 88

In its Publications 56, 67, 69, 71, and 72, ICRP has provided age-specific biokinetic models and, using those models, compiled dose coefficients (doses per unit intake) for intakes of radionuclides by members of the public. Committed effective doses for the inhalation or ingestion of radionuclides by workers who are occupationally exposed were given in Publication 68 based on the most recent dosimetric and biokinetic models for adults. Additionally, a compilation of dose coefficients for both workers and members of the public has been issued on a CD-ROM. The present report complements that series by addressing doses to the embryo/fetus after intakes of radionuclides by a female member of the public or a female worker, before or during pregnancy. Ingestion and inhalation of selected radionuclides of the 31 elements for which age-dependent biokinetic models were provided in the previous reports are considered. These elements are H, C, S, Ca, Fe, Co, Ni, Zn, Se, Sr, Zr, Nb, Mo, Tc, Ru, Ag, Sb, Te, I, Cs, Ba, Ce, Pb, Po, Ra, Th, U, Np, Pu, Am, and Cm. New biokinetic and dosimetric models for calculating doses to the developing embryo and fetus are developed and used in conjunction with the models for infants, children, and adults presented in the previous reports. The models used take account of transfer of radionuclides across the placenta, distribution and retention of radionuclides in fetal tissues, growth of the fetus, and photon irradiation from radionuclides in the placenta and maternal tissues. Human and animal data are used as available in the development of these models. Intake scenarios comprising single or continuous maternal intakes are taken into account in the compilation of effective dose coefficients following ingestion or inhalation of the radionuclides considered. A CD-ROM with more comprehensive information on doses from inhalation of different particle sizes, tissue doses, and doses at various times after birth has been developed concurrently with the report and will be available shortly. The report does not consider doses to the offspring due to intakes of radionuclides in maternal milk and external irradiation from the mother's body after birth. The radiation sensitivity of the offspring is not discussed.

Basis and implications of the ICRP's new biokinetic model for thorium. International Commission on Radiological Protection.

The International Commission on Radiological Protection (ICRP) has adopted a new, age-specific biokinetic model for thorium, along with new assumptions concerning the fate of radioactive progeny produced in the body after intake of thorium. This paper explains the basis for the model and assumptions and examines some of their implications with regard to radiation dosimetry and bioassay. The new model differs substantially from the ICRP's previous biokinetic model for thorium (introduced in 1979 in ICRP Publication 30) with regard to model structure, sources of data used to derive parameter values, predictions of integrated activities of long-lived thorium isotopes in some radiosensitive organs, and predictions of the rates of urinary and fecal excretion of thorium at times remote from exposure. For the case of injection of 232Th into blood of an adult, the new model and assumptions yield 4- to 8-fold decreases in predictions of 50-y committed equivalent doses to radiosensitive skeletal tissues but 7- to 55-fold increases in predictions of committed equivalent doses to extra-skeletal tissues, compared with the model and treatment of decay chain members recommended in ICRP Publication 30.

Chelation of Toxic Metals: Current Interests

Research ArticleOpen AccessChelation of toxic metals: current interests.is accompanied byRole of chelating agents for prevention, intervention, and treatment of exposures to toxic metals. R A Goyer R A Goyer National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA. Search for more papers by this author Published:1 November 1995https://doi.org/10.1289/ehp.95103988Cited by:9AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit "Chelation of toxic metals: current interests.." Environmental Health Perspectives, 103(11), pp. 988–989FiguresReferencesRelatedDetailsCited by Kumar N, Soni S, Singh T, Kumar A, Ahmad F, Bhatnagar A and Mittal G (2015) Development and Optimization of Gastro-Retentive Controlled-Release Tablet of Calcium-Disodium Edentate and its In Vivo Gamma Scintigraphic Evaluation, AAPS PharmSciTech, 10.1208/s12249-014-0272-y, 16:6, (1270-1280), Online publication date: 1-Dec-2015. Quig D (2013) Metal Toxicity Textbook of Natural Medicine, 10.1016/B978-1-4377-2333-5.00023-7, (191-199), . Kumar N, Soni S, Jaimini A, Ahmad F, Bhatnagar A and Mittal G (2011) Edetate calcium disodium nanoparticle dry powder inhalation: A novel approach against heavy metal decorporation, International Journal of Pharmaceutics, 10.1016/j.ijpharm.2011.06.038, 416:1, (376-383), Online publication date: 1-Sep-2011. Puntarulo S (2005) Iron, oxidative stress and human health, Molecular Aspects of Medicine, 10.1016/j.mam.2005.07.001, 26:4-5, (299-312), Online publication date: 1-Aug-2005. Conzone S, Hall M, Day D and Brown R (2004) Biodegradable radiation delivery system utilizing glass microspheres and ethylenediaminetetraacetate chelation therapy, Journal of Biomedical Materials Research, 10.1002/jbm.a.30076, 70A:2, (256-264), Online publication date: 1-Aug-2004. Rao A, Prasad V and Sood P (2016) Monothiols and Vitamins are Ideal Therapeutic Agents for Mercury Elimination from Nervous and Non-Nervous Tissues of Fish, Nutritional Neuroscience, 10.1080/1028415X.1998.11747248, 1:5, (383-390), Online publication date: 1-Jan-1998. Pounds J and Leggett R (2018) The ICRP age-specific biokinetic model for lead: validations, empirical comparisons, and explorations., Environmental Health Perspectives, 106:suppl 6, (1505-1511), Online publication date: 1-Dec-1998. Muir M (1997) Current Controversies in the Diagnosis and Treatment of Heavy Metal Toxicity, Alternative and Complementary Therapies, 10.1089/act.1997.3.170, 3:3, (170-178), Online publication date: 1-Jun-1997. RENCOVA, V. SVOBODA, R. HOLUSA, V. J (2009) Reduction of subacute lethal radiotoxicity of polonium-210 in rats by chelating agents, International Journal of Radiation Biology, 10.1080/095530097143338, 72:3, (341-348), Online publication date: 1-Jan-1997. Related articlesRole of chelating agents for prevention, intervention, and treatment of exposures to toxic metals.1 November 1995Environmental Health Perspectives Vol. 103, No. 11 November 1995Metrics About Article Metrics Publication History Originally published1 November 1995Published in print1 November 1995 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Basis for the ICRPʼs Age-specific Biokinetic Model for Uranium

In an effort motivated largely by the Chernobyl nuclear accident, the International Commission on Radiological Protection (ICRP) is developing age-specific biokinetic models and dose coefficients for environmentally important radionuclides. This paper describes the ICRP's age-specific biokinetic model for uranium. The model is constructed within a physiologically based framework originally developed for application to the alkaline earth elements but sufficiently general to apply to the larger class of bone-volume-seeking elements. Transfer rates for a reference adult are based mainly on: 1. measurements of uranium in blood and excreta of several human subjects who were intravenously injected with uranium; 2. postmortem measurements of uranium in tissues of some of those subjects; 3. postmortem measurements of uranium in tissues of occupationally and non-occupationally exposed subjects; 4. data on baboons, dogs, and smaller laboratory animals exposed to uranium for experimental purposes; and 5. consideration of the physiological processes thought to control retention and translocation of uranium in the body. Transfer rates for the adult are extended to children by application of a set of generic assumptions applied by the ICRP to calcium-like elements. These assumptions were derived mainly from observations of the age-specific biokinetics of the alkaline earth elements and lead in humans and laboratory animals but are consistent with available age-specific biokinetic data on uranium.

An Age-Specific Kinetic Model of Lead Metabolism in Humans

Although considerable progress has been made in recent years in reducing human exposures to lead, the potential for high intake of this contaminant still exists in millions of homes and in many occupational settings. Moreover, there is growing evidence that levels of lead intake considered inconsequential just a few years ago can result in subtle, adverse health effects, particularly in children. Consequently, there have been increased efforts by health protection agencies to develop credible, versatile methods for relating levels of lead in environmental media to levels in blood and tissues of exposed humans of all ages. In a parallel effort motivated largely by the Chernobyl nuclear accident, the International Commission on Radiological Protection (ICRP) is assembling a set of age-specific biokinetic models for calculating radiation doses from environmentally important radionuclides, including radioisotopes of lead. This paper describes a new age-specific biokinetic model for lead originally developed for the ICRP but expanded to include additional features that are useful for consideration of lead as a chemical toxin. The model is developed within a generic, physiologically motivated framework designed to address a class of calciumlike elements. This framework provides a useful setting in which to synthesize experimental, occupational, and environmental data on lead and exploit common physiological properties of lead and the alkaline earth elements. The modular design is intended to allow researchers to modify specific parameter values or model components to address special problems in lead toxicology or to incorporate new information. Transport of lead between compartments is assumed to follow linear, first-order kinetics provided the concentration in red blood cells remains below a nonlinear threshold level, but a nonlinear relation between plasma lead and red blood cell lead is modeled for concentrations above that level. The model is shown to be consistent with data on human subjects exposed to lead under a variety of experimental and natural conditions.

An age-specific kinetic model of lead metabolism in humans.

Although considerable progress has been made in recent years in reducing human exposures to lead, the potential for high intake of this contaminant still exists in millions of homes and in many occupational settings. Moreover, there is growing evidence that levels of lead intake considered inconsequential just a few years ago can result in subtle, adverse health effects, particularly in children. Consequently, there have been increased efforts by health protection agencies to develop credible, versatile methods for relating levels of lead in environmental media to levels in blood and tissues of exposed humans of all ages. In a parallel effort motivated largely by the Chernobyl nuclear accident, the International Commission on Radiological Protection (ICRP) is assembling a set of age-specific biokinetic models for calculating radiation doses from environmentally important radionuclides, including radioisotopes of lead. This paper describes a new age-specific biokinetic model for lead originally developed for the ICRP but expanded to include additional features that are useful for consideration of lead as a chemical toxin. The model is developed within a generic, physiologically motivated framework designed to address a class of calciumlike elements. This framework provides a useful setting in which to synthesize experimental, occupational, and environmental data on lead and exploit common physiological properties of lead and the alkaline earth elements. The modular design is intended to allow researchers to modify specific parameter values or model components to address special problems in lead toxicology or to incorporate new information. Transport of lead between compartments is assumed to follow linear, first-order kinetics provided the concentration in red blood cells remains below a nonlinear threshold level, but a nonlinear relation between plasma lead and red blood cell lead is modeled for concentrations above that level. The model is shown to be consistent with data on human subjects exposed to lead under a variety of experimental and natural conditions.

An Elementary Method for Implementing Complex Biokinetic Models

Recent efforts to incorporate greater anatomical and physiological realism into biokinetic models have resulted in many cases in mathematically complex formulations that limit routine application of the models. This paper describes an elementary, computer-efficient technique for implementing complex compartmental models, with attention focused primarily on biokinetic models involving time-dependent transfer rates and recycling. The technique applies, in particular, to the physiologically based, age-specific biokinetic models recommended in Publication No. 56 of the International Commission on Radiological Protection, Age-Dependent Doses to Members of the Public from Intake of Radionuclides.

An Elementary Method for Solving Compartmental Models with Time-Dependent Coefficients

Several of the biokinetic models used in ICRP Publication 56, Age-dependent Doses to the Public from Exposures to Radionuclides, depict the movement of materials among explicitly defined organs and tissues using transfer coefficients that vary continuously with age from infancy to adulthood. Such physiologically and/or biologically based models are appealing because of the identifiability of model components, but their application has been limited by the general perception that such models can only be evaluated using sophisticated mathematical tools. The purpose of this paper is to describe an elementary method for solving complex compartmental models with time-dependent transfer coefficients. The method has practically no limitations on the number of compartments or connections between compartments and thus is applicable to a wide class of models, including those that depict recycling of material. We illustrate the method by applications to the age-specific biokinetic models described in ICRP Publication 56.

An Elementary Method for Solving Compartmental Models with Time-Dependent Coefficients

Several of the biokinetic models used in ICRP Publication 56, Age-dependent Doses to the Public from Exposures to Radionuclides, depict the movement of materials among explicitly defined organs and tissues using transfer coefficients that vary continuously with age from infancy to adulthood. Such physiologically and/or biologically based models are appealing because of the identifiability of model components, but their application has been limited by the general perception that such models can only be evaluated using sophisticated mathematical tools. The purpose of this paper is to describe an elementary method for solving complex compartmental models with time-dependent transfer coefficients. The method has practically no limitations on the number of compartments or connections between compartments and thus is applicable to a wide class of models, including those that depict recycling of material. We illustrate the method by applications to the age-specific biokinetic models described in ICRP Publication 56.