Updating the icrp human respiratory tract model
The consequences of the use of these values were investigated by calculating related committed effective doses per unit intake.Average and median estimates were calculated for f for each plutonium compound, that can be used as default values for specific chemical forms instead of the current reference types.
In workers who had been removed from exposure, the rate of urinary excretion of U increased for a few months, peaked, and then declined at a rate consistent with moderately soluble material.For some long-lived radionuclides in relatively insoluble form (type S), this increased retention increases the lung dose per unit intake by 50–100% compared to the HRTM value.As part of an epidemiological study, doses from intake of radionuclides were estimated for workers employed during a 52-year period at the Rocketdyne/Atomics International facility in California.To obtain default parameter values for general use, the model was fitted to data from the three recent studies, and also the experimental data used in development of the HRTM to define particle transport from the AI region for the first year after intake.The result of the analysis is that about 40% of the AI deposit of insoluble particles is sequestered in the interstitium and the remaining fraction is cleared to the ciliated airways with a half-time of about 300 days.This study derives specific values of absorption rates for different chemical forms of plutonium from in vitro and animal (monkeys, dogs, mice, rats) experiments, and from human contamination cases.
Different published experimental data have been reinterpreted here to derive values for the absorption parameters, f, used in the human respiratory tract model currently adopted by the International Commission on Radiological Protection (ICRP).
The model was originally published in 1966, modified slightly in Publication No. Research has also provided sufficient information for a revision of the model.
The task group's approach has been to review, in depth, morphology and physiology of the respiratory tract; deposition of inhaled particles in the respiratory tract; clearance of deposited materials; and the nature and specific sites of damage to the respiratory tract caused by inhaled radioactive substances.
Workers may be exposed to various chemical forms and isotopic compositions of Pu.
In 1984, the International Commission on Radiological Protection (ICRP) appointed a task group of Committee 2 to review and revise, as necessary, the ICRP Dosimetric Model for the Respiratory System. The task group concluded that research during the past 20 y suggested certain deficiencies in the ICRP Dosimetric Model for the Respiratory System.
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