Permissible Concentration In Air Research Articles

39th Lauriston S. Taylor Lecture: Dosimetry of Internal Emitters: Contribution of Radiation Protection Bodies and Radiological Events.

Since the early days of the Manhattan Engineer District, Oak Ridge National Laboratory (ORNL) has served to advance the dosimetry models used to set protection standards for radionuclides taken into the body. Throughout the years, this effort benefited significantly from ORNL staff's active participation in national and international scientific bodies. The first such interaction was in 1946 with the National Committee on Radiation Protection (NCRP), chaired by L.S. Taylor, which led to the 1949 to 1953 series of tripartite conferences of experts from Canada, the United Kingdom, and the United States. These conferences addressed the need for standardization of dosimetry models and led to the establishment of an anatomic and physiologic model called "Standard Man," a precursor of the reference worker defined in Publication 23 of the International Commission on Radiological Protection (ICRP). Standard Man was used in setting the maximum permissible concentrations in air and water published in NBS Handbook 52 and subsequent reports by NCRP and ICRP. K.Z. Morgan, then director of the Health Physics Division at ORNL, participated in the tripartite conferences and subsequently established ORNL as a modeling and computational resource for development of radiation protection standards. ORNL's role expanded with participation in the work of the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine. Results of interactions with the MIRD Committee are evident in the radiation protection guidance for internal emitters in ICRP Publication 30. The annual limit on intake and derived air concentration values tabulated in Publication 30 were computed by an ORNL-based task group of ICRP Committee 2. A few years after the appearance of Publication 30, the Chernobyl nuclear reactor accident made clear the need to develop standard dosimetry models for pre-adult ages as members of the public. In the late 1980s, ICRP began an effort to extend its reference worker concept to a reference family and develop dosimetric models for application to intake of radionuclides by members of the public. However, the modeling approach underlying the ICRP Publication 30 computational framework was not amenable to age and gender considerations. With support of U.S. federal agencies, ORNL had begun efforts in the early 1980s to develop age- and gender-specific dosimetric models, including physiologically informed biokinetic models and age-specific dosimetric phantoms. ORNL's models and methods became the starting point for the ICRP's series of reports on dose coefficients for radionuclide intake by the public. Currently ICRP Committee 2 is overseeing development of a second generation of post-Chernobyl models and methods, with updates of Publications 30 and 68 soon to appear and new models for members of the public in preparation. The focus of this Lauriston S. Taylor Lecture is to chronicle advancements in the dosimetry of internal emitters with some discussion of models and methods but with due deference to decisions within scientific bodies and stimulated by radiological events.

A Proposed Multi-detector Method for Prompt 90Sr Detection in Post-accident Environmental Matrices

Strontium-90 is of relevant biological importance among fission products released during a fission reactor accident. Rapid information on its concentration in environmental matrices is extremely valuable, yet this implies chemical separations and handling with a shift in daughter equilibrium and therefore the need to wait a sufficient time for the equilibrium to be reestablished. The work concerns a feasibility study of a multi-detector system for a prompt evaluation of the 90Sr activity or, at least, a prompt determination of its order of magnitude in the presence of other pure beta and beta-gamma emitters; their interferences are examined on the basis of the Chernobyl releases and their decay properties. The technique is based on a plastic scintillator beta detector and a guard ring of BGO counters which can be logically connected in coincidence and anticoincidence. The evaluations show that a few hours are sufficient to determine a specific activity comparable with the Maximum Permissible Concentration in air by sampling 10 m3.

Permissible concentrations of chemicals in air and water derived from RTECS entries: a "rash" chemical scoring system.

Many chemicals are of concern to human health, but only a few have epidemiologically derived risk estimates. About 45,000 chemicals are listed in RTECS, most of which have had some testing in subhuman models. RTECS entries range from cellular effects through organoleptic damage to lethality, with many pathological endpoints listed, including mutagenic changes, irritation, teratogenesis, cancer, mortality, etc. However, it is difficult to extend any biological test results to human risk assessments. If the results are extended, the degree of validity is highly uncertain. This paper describes a logical basis for using the entire complex spectrum of test results to evaluate the overall toxicological potency of a chemical to be assayed (i.e., an interviewing chemical) and describes how to derive tentative, permissible concentrations in air and water for any particular chemical for which no regulatory guidance exists. This approach has been tested for 16 reference chemicals discussed in NIOSH Criteria Documents, EPA-CAG reports, etc. The evaluations are uncomplicated, but occasionally it is difficult to match RTECS entries for two different chemicals. Difficult comparisons may require some familiarity with experimental design and the toxicological literature. One important product of this novel approach is that a distribution or array of potency values is obtained for any chemical evaluated. This distribution reflects many uncertainties stemming from low statistical power, experimental design, pharmacological processes, interspecies variability, dose rate, biological effect monitored, route of treatment, etc. The array of relative values for a particular chemical reflects many different biological and physical conditions. The distribution of the array helps to index a composite toxicological profile for many different biological effects resulting from numerous treatment protocols. To minimize the effect of extreme sensitivity of certain (perhaps novel) biological test models, possible errors in the RTECS data-base, and possible human pharmacological insensitivity to a particular chemical and/or a particular route of administration, we consider the interquartile range (i.e., the central 50%) of the array of relative potency values between two chemicals being compared as a practical measure of uncertainty. Thus, the range in response derived from variability in relative potency should be useful in addressing the range of response in man as estimated from extrapolations of test data.

Air activation produced by high-energy medical accelerators.

The activity of 15O and 13N per unit volume of air produced by a 25 and a 45-MeV medical accelerator was determined by direct measurement. The accelerators were operated in such a fashion as to produce maximum activation of the treatment room air. Levels of the order of 1% or less of the maximum permissible concentration in air for 15O and 13N were found immediately after accelerator shutdown. Three different techniques for calibrations of the air detector were investigated.

Calculated MPCa Values For 239PuO2 by Comparing the Added Risk of Cancer With the Accepted Occupational Risks

The maximum permissible concentration in air (MPCa) values for 239Pu02 are calculated on the basis of the generally accepted fatality rate during occupational hours. The risk of contracting cancer is taken instead of this fatality risk. The cancer induction risk to the bone, the lungs, the liver, and the tracheobronchial lymph nodes is examined. Two deposition and distribution models are used: the lung model presented in ICRP publication 19 and a modification of this model, which corrects for the influence of particle size on the rate of removal from the lungs. Our results indicate that reduction of the ICRP publication 2 MPCMa value by a factor of 7–70 is justifiable.

Book reviewsCesium–137 from the environment to man: metabolism and dose. N.C.R.P. Report 52, pp. v+48, 1977 (N.C.R.P., Washington), $3.00.

This latest addition to the N.C.R.P. report series deals with metabolism and dosimetry of 137Cs which, because of its relatively long half-life and ready uptake into the body through food chains, is prominent in all considerations of the consequences of radioactive fall-out. The report comprises four main chapters which concern: (a) the relationships between 137Cs in the environment and in man, (b) the dosimetry of internally incorporated 137Cs in man, (c) the derivation of the dose limits and maximum permissible concentrations in air and water for occupational exposure and (d) effects observed in two experiments on dogs injected with 137Cs. The report concludes with a short summary.

Determination of airborne mercury-203

A method is described for the determination of airborne compounds of203Hg. The method is based on the sorption of Hg on hopcalite (activated copper oxide/manganese oxide) with subsequent monitoring for the gamma-radiation of203Hg. Aerosol activity in the air is separated by sucking the air through a filter prior to the absorption tube. The sensitivity of the method permits the assessment of less than one tenth of the maximum permissible concentration in air. It is shown experimentally that the separation procedure used is suitable for the determination of airborne mercuric acetate and its thermal decomposition products.

Specification of units for natural uranium and natural thorium. Statement of the national council on radiation protection and measurements (NCRP).

Feeling that the use of the “special” curie for natural uranium and thorium has led to confusion, the NCRP recommends that this unit be replaced by units of mass. Previously stated values of the maximum permissible body burden (MPBB) and maximum permissible concentration in air and water (MPC) for uranium may be converted to mass units by multiplying them by 3 × 106 γg per “special” microcurie. Since the isotopic composition of natural thorium is not constant, the NCRP recommends that established MPBB and MPC values for each individual isotope be used instead of defining a limiting concentration for all natural thorium.

A Five-year Inhalation Study with Natural Uranium Dioxide (UO2) Dust-II. Postexposure Retention and Biologic Effects in the Monkey, Dog and Rat

Inhalation studies show that dogs, monkeys, and rats can breathe a natural uranium dioxide aerosol of approximately 1 mu m mass median particle diameter at a mean concentration of 5 mg U/m/sup 3/ (25 x Threshold Limit Value or 28 x Maximum Permissible Concentration in Air) for periods as long as 5 yr with little evidence of serious injury (L. J. Leach et al., Health Phys. 18: postexposure periods during which pulmonary neoplasia developed in a high percentage of the dogs examined 2 to 6 yr after exposure. Pulmonary and tracheobronchial lymph node fibrosis, consistent with radiation effects, apparently dose dependent, and more marked in monkeys than in dogs was also noted. No evidence of uranium toxicity was found in records of body weights, mortality, various hematologic parameters, or the histologic condition of the kidneys. (auth)

The exposure of United Kingdom miners to radon.

<b>Duggan, M.J., Soilleux, P.J., Strong, J.C., and Howell, D.M. (1970).</b><i>Brit. J. industr. Med.,</i><b>27,</b> 106-109. <b>The exposure of United Kingdom miners to radon.</b> Airborne radon has been recognized as a probable cause of lung cancer since the epidemiological studies made in the mining communities of Schneeberg and Jachymov during the 1920s and 1930s. Uranium miners are generally exposed to high concentrations of radon, and the growth of the uranium mining industry in the past 20 years has therefore stimulated a great amount of work on the risk from inhalation of radon and its daughters. However, there is still no general agreement on either the physical measurements in which the maximum permissible concentration in air should be expressed or the numerical value of this concentration. There are no uranium mines being worked in the United Kingdom but there are considerable numbers of coal and other mines. It was therefore decided to make some radon measurements in a selection of mines in the UK to see if there was any prospect of obtaining useful dose-risk data. Measurements were made in 22 mines in all - 12 coal mines and 10 other mines - and the highest concentrations were found in three haematite mines in West Cumberland and in the two tin mines which were visited. The concentrations in these five mines were, in general, greater than 0·3 of a working level (WL) and in many locations were greater than 1 WL. Because of these findings and also because an excess incidence of lung cancer among West Cumberland haematite miners has been previously reported, a further study of the mortality experience of West Cumberland miners has been carried out by Boyd, Doll, Faulds, and Leiper (1970). Their findings are reported in this Journal (p. 97).

A Case of Accidental Inhalation of Irradiated Uranium

A case of accidental inhalation of irradiated uranium was studied by body radioactivity measurement for 850 days. The whole-body retentions of 137Cs, 95Zr/95Nb, 103Ru and 141Ce + 144Ce were all measured; the biological half-lives were 113 days, 250 days, ≮ 230 days and ≮ 2,800 days for these radionuclides respectively. The results suggested that after the first week there were no major changes in the distribution of the radioactivity in vivo, although there may have been some translocation of the cerium from lung to lymph nodes. The 137Cs content was used to estimate a lower limit for the amount of uranium deposited initially in the lung, while the 95Zr content six days after inhalation was used to estimate the amount of uranium retained. The latter was probably not more than 6 per cent of the former. The fate of the uranium was unknown. The implications of the findings to the calculation of maximum permissible concentrations in air of insoluble radioactive material are discussed. Some recommendations are...

A CASE OF ACCIDENTAL INHALATION OF IRRADIATED URANIUM.

A case of accidental inhalation of irradiated uranium was studied by body radioactivity measurement for 850 days. The whole-body retentions of 137Cs, 95Zr/95Nb, 103Ru and 141Ce + 144Ce were all measured; the biological half-lives were 113 days, 250 days, ≮ 230 days and ≮ 2,800 days for these radionuclides respectively. The results suggested that after the first week there were no major changes in the distribution of the radioactivity in vivo, although there may have been some translocation of the cerium from lung to lymph nodes. The 137Cs content was used to estimate a lower limit for the amount of uranium deposited initially in the lung, while the 95Zr content six days after inhalation was used to estimate the amount of uranium retained. The latter was probably not more than 6 per cent of the former. The fate of the uranium was unknown. The implications of the findings to the calculation of maximum permissible concentrations in air of insoluble radioactive material are discussed. Some recommendations are made for the investigations of possible future cases, to eliminate some of the speculation involved in the present discussion.

BIOLOGICAL HALF-LIFE OF CAESIUM IN MAN IN ACUTE AND CHRONIC EXPOSURE.

THE biological half-life of an element in man is needed for the calculation of maximun permissible concentrations in air and water of radioisotopes of the element1. An important assumption in making such calculations is that the body content during chronic exposure may be predicted by mathematical integration with respect to time of the equation describing the retention following a single acute intake. This hypothesis has never been tested in man. The results of recent investigations here demonstrate the essential correctness of the assumption for radioisotopes of caesium.

原子炉より放出される放射性アルゴン

The conditions necessary and sufficient for the radiation monitoring are investigated, when a considerable amount of radioactive argon is continuously released from reactors. According to the present regulation the maximum permissible concentration in air of 41A is 5×10-7μc/ml occupationally, and it is expected to be reduced before long. In any case, it is commonly regarded as necessary to detect the concentration of 41A upto about 10-8μc/ml in the case of the monitoring for the public living in the neigborhood of a reactor site. And such a detector necessarily costs much and is troublesome for the practical use, even if it is technically feasible. In this paper, it is shown on the analysis of the effect of 41A that there is the possibility to practice the monitoring for the public, only with the devices detectable for the local concentration about 10-65×10-7μc/ml and γ detectors of the standard type. It is also mentioned that the contribution of 41A to the genetic dose of the population might be detectable.