Assessing risk communication effectiveness: perspectives of agency practitioners

A study conducted by the Agency for Toxic Substances and Disease Registry (ATSDR), a US public health agency, evaluated ATSDR's risk communication process, specifically the roles and responsibilities, planning, implementation, and coordination of activities in response to illegal indoor spraying of methyl parathion, a hazardous pesticide, in Pascagoula, MS. Interviews of staff members involved in the intervention were conducted and an analysis revealed strengths and areas in need of improvement in the design and implementation of risk communication strategies. Key recommendations included developing a clear strategy for planning and conducting communication activities; determining staff roles and responsibilities for coordination; and developing clear and consistent health messages, a dissemination strategy, and training in the delivery and evaluation of messages, effects, and outcomes.

Aerosols generated during beryllium machining

Some beryllium processes, especially machining, are associated with an increased risk of beryllium sensitization and disease. Little is known about exposure characteristics contributing to risk, such as particle size. This study examined the characteristics of beryllium machining exposures under actual working conditions. Stationary samples, using eight-stage Lovelace Multijet Cascade Impactors, were taken at the process point of operation and at the closest point that the worker would routinely approach. Paired samples were collected at the operator's breathing zone by using a Marple Personal Cascade Impactor and a 35-mm closed-faced cassette. More than 50% of the beryllium machining particles in the breathing zone were less than 10 microns in aerodynamic diameter. This small particle size may result in beryllium deposition into the deepest portion of the lung and may explain elevated rates of sensitization among beryllium machinists.

Modular glovebox connector and associated good practices for control of radioactive and chemically toxic materials

Design and associated good practices are described for a modular glovebox connector to improve control of radioactive and chemically toxic materials. The connector consists of an anodized aluminum circular port with a mating spacer, gaskets, and retaining rings for joining two parallel ends of commercially available or custom-manufactured glovebox enclosures. Use of the connector allows multiple gloveboxes to be quickly assembled or reconfigured in functional units. Connector dimensions can be scaled to meet operational requirements for access between gloveboxes. Options for construction materials are discussed, along with recommendations for installation of the connector in new or retrofitted systems. Associated good practices include application of surface coatings and caulking, use of disposable glovebags, and proper selection and protection of gasket and glove materials. Use of the connector at an inhalation toxicology research facility has reduced the time and expense required to reconfigure equipment for changing operational requirements, the dispersion of contamination during reconfigurations, and the need for decommissioning and disposal of contaminated enclosures.

Chronic cigarette smoke exposure increases the pulmonary retention and radiation dose of 239Pu inhaled as 239PuO2 by F344 rats

As a portion of a study to examine how chronic cigarette smoke exposure might alter the risk of lung tumors from inhaled 239puO2 in rats, the effects of smoke exposure on alpha-particle lung dosimetry over the life-span of exposed rats were determined. Male and female rats were exposed to inhaled 239PuO2 alone or in combination with cigarette smoke. Animals exposed to filtered air alone served as controls for the smoke exposure. Whole-body exposure to mainstream smoke diluted to concentrations of either 100 or 250 mg total particulate matter m(-3)(LCS or HCS, respectively) began at 6 wk of age and continued for 6 h d(-1), 5d wk(-1), for 30 mo. A single, pernasal, acute exposure to 239PuO2 was given to all rats (control, LCS and HCS) at 12 wk of age. Exposure to cigarette smoke caused decreased body weight gains in a concentration dependent manner. Lung-to-body weight ratios were increased in smoke-exposed rats. Rats exposed to cigarette smoke before the 239PuO2 exposure deposited less 239Pu in the lung than did controls. Except for male rats exposed to LCS, exposure to smoke retarded the clearance of 239Pu from the lung compared to control rats through study termination at 870 d after 239PuO2 exposure. Radiation doses to lungs were calculated by sex and by exposure group for rats on study for at least 360 d using modeled body weight changes, lung-to-body weight ratios, and standard dosimetric calculations. For both sexes, estimated lifetime radiation doses from the time of 239PuO2 exposure to death were 3.8 Gy, 4.4 Gy, or 6.7 Gy for the control, LCS, or HCS exposure groups, respectively. Assuming an approximately linear dose-response relationship between radiation dose and lung neoplasm incidence, approximate increases of 20% or 80% in tumor incidence over controls would be expected in rats exposed to 239PuO2 and LCS or 239PuO2 and HCS, respectively.

Carcinogenic responses of transgenic heterozygous p53 knockout mice to inhaled 239PuO2 or metallic beryllium

The transgenic heterozygous p53+/- knockout mouse has been a model for assessing the tumorigenicity of selected carcinogens administered by noninhalation routes of exposure. The sensitivity of the model for predicting cancer by inhaled chemicals has not been examined. This study addresses this issue by acutely exposing p53+/- mice of both sexes by nose-only inhalation to either air (controls), or to 1 of 2 levels of 239PuO2 (500 or 100 Bq 239Pu) or beryllium (Be) metal (60 or 15 micrograms). Additional wild-type p53+/+ mice were exposed by inhalation to either 500 Bq of 239PuO2 or 60 micrograms of Be metal. These carcinogens were selected because they operate by differing mechanisms and because of their use in other pulmonary carcinogenesis studies in our laboratory. Four or 5 of the 15 mice per sex from each group were sacrificed 6 mo after exposure, and only 2 pulmonary neoplasms were observed. The remainder of the mice were held for life-span observation and euthanasia as they became moribund. Survival of the p53+/- knockout mice was reduced compared to the p53+/+ wild-type mice. No lung neoplasms were observed in p53+/- mice exposed to air alone. Eleven of the p53+/- mice inhaling 239PuO2 developed pulmonary neoplasms. Seven p53+/+ mice exposed to 239PuO2 also developed pulmonary neoplasms, but the latency period for pulmonary neoplasia was significantly shorter in the p53+/ mice. Four pulmonary neoplasms were observed in p53+/- mice exposed to the higher dose of Be, whereas none were observed in the wild-type mice or in the heterozygous mice exposed to the lower dose of Be. Thus, both p53+/- and p53+/+ mice were susceptible to 239Pu-induced carcinogenesis, whereas the p53+/- but not the p53+/+ mice were susceptible to Be-induced carcinogenesis. However, only 2 pulmonary neoplasms (1 in each of the 239PuO2 exposure groups) were observed in the 59 p53+/ mice that were sacrificed or euthanatized within 9 mo after exposure, indicating that the p53+/- knockout mouse might not be appropriate for a 6-mo model of carcinogenesis for these inhaled carcinogens.

Dose-response relationships between inhaled beryllium metal and lung toxicity in C3H mice

Inhaled beryllium (Be) can induce a range of adverse pulmonary responses in animals and humans including acute pneumonitis, chronic granulomatous lung disease, and cancer. To facilitate comparisons with our previous data describing Be toxicity in rats, we evaluated the toxic effects of inhaled Be metal in mice. Groups of 34 strain C3H/HeJ mice were acutely exposed by the nose-only route to aerosolized Be metal to achieve measured initial lung burdens of 0, 1.7, 2.6, 12, or 34 microg. All mice received aerosolized 85 Sr-labeled fused aluminosilicate particles (85 Sr-FAPs) immediately before their Be exposure so that the influence of Be on lung retention of these poorly soluble tracer particles could be externally quantitated. Groups of mice were euthanized at 8, 15, 40, 90, 210, and 350 days after exposure for evaluation of histopathological changes and for cytologic and biochemical indicators of lung damage measured in bronchoalveolar lavage fluid. Clearance of 85 Sr-FAP tracer particles through 196 days after exposure was delayed in mice receiving the 12 and 34 microg Be lung burdens, but not the 1.7 or 2.6 microg lung burdens. Increased total cell numbers, increased percentage of neutrophils, and elevated levels of total protein and the activities of beta-glucuronidase and lactate dehydrogenase in bronchoalveolar lavage fluid were observed in the two highest Be lung burden groups compared with controls. Lung lesions included particle-containing macrophages, granulomatous pneumonia, lymphocytic interstitial aggregates, and mononuclear interstitial infiltrates. These lesions were occasionally seen in mice receiving the 2.6 microg lung burden, were present in most of the mice receiving 12 or 34 microg lung burdens, and were generally increased in severity with time and lung burden. Thus, we have demonstrated that a single, acute inhalation exposure to Be metal can chronically retard particle clearance and induce lung damage in mice. The initial lung burdens used caused responses ranging from no apparent effects to significant Be-induced responses. A comparison of these data with our previous data from rats indicates that the mass of Be metal required to induce lung damage in mice is similar to that needed for rats. When expressed on a lung weight-normalized basis, mice appeared to be more resistant to the toxic effects of inhaled Be than rats.

Immunologic specificity of lymphocyte cell lines from dogs exposed to beryllium oxide

We have reported that dogs exposed twice to aerosols of beryllium oxide (BeO) developed Be-specific immune responses within the lung, along with granulomatous and fibrotic lung lesions. To evaluate the specificity of the immune response, lymphocytes from lungs and blood of BeO-exposed dogs were co-cultured over an irradiated blood monocyte layer, alternately with interleukin 2 and BeSO4. Resultant cell lines were then tested for their response to different metal cations, common canine recall antigens, and BeSO4 in an in vitro cell proliferation assay. The cell lines responded to BeSO4 in a dose-dependent fashion, with mean stimulation indices of 7, 58, 119, and 112 at concentrations of 0.01, 1.0, 10, and 100 microM BeSO4 respectively. Cells not proliferate when incubated with ZnSO4 or NiSO4, or with canine distemper, leptospira, adenovirus 2, parvovirus, or parainfluenza antigens. Lymphocytes from normal vaccinated dogs proliferated markedly when cultured with these antigens. Cells from the cultured cell lines (91%) stained with Thy-1 (a pan T-cell marker) and 96% stained with DT2 (a helper T-cell marker). Furthermore, the Be-induced proliferative response was restricted by major histocompatibility (MHC) class II antigens. These data reinforce the premise that inhalation exposure of dogs to BeO produces lung lesions and MHC class II restricted immunologic responses mediated by Be-specific, helper T-Cells. These data further confirm the hypothesis that antigen localized to the lung results in the recruitment of T-cells to the lung, followed by localized antigen-specific, cell-mediated immune responses.

Chronic granulomatous pneumonia and lymphocytic responses induced by inhaled beryllium metal in A/J and C3H/HeJ mice

Inhalation of beryllium (Be) has been associated with 2 syndromes: an acute chemical pneumonitis and a granulomatous lung disease known as chronic beryllium disease (CBD). Key to the pathogenesis of CBD is a delayed-type hypersensitivity reaction, in which Be most likely functions as a hapten and acts as a Class II-restricted antigen, stimulating local proliferation and accumulation in the lung of Be-specific CD4+ T cells. The purpose of this study was to establish a mouse model of CBD using the inhalation route of exposure. A/J (H-2a haplotype) and C3H/HeJ (H-2a) mice were exposed once for 90 min in nose-only exposure tubes to aerosols of Be metal. Six mo later, lung histopathologic responses were assessed. Further analyses defined the phenotypic profile of lymphocytes in pulmonary lesions and evaluated proliferation of lymphocytes in situ and in response to Be in vitro. Responses were similar in both strains of mice. The lungs of all Be-exposed mice had interstitial compact aggregates of lymphocytes, and granulomatous pneumonia characterized by vacuolated macrophages and giant cells in alveoli, neutrophils in alveoli and alveolar septa, multifocal interstitial granulomas, and interstitial infiltrates of lymphocytes, plasma cells, monocytes, and macrophages. Most Be-exposed mice had minimal to mild interstitial fibrosis. The majority of lymphocytes in interstitial infiltrates and in microgranulomas were CD4+ T cells. Interstitial compact aggregates of lymphocytes contained B cells centrally and CD4+ cells peripherally. Lymphocyte labeling indices, used to assess proliferation in situ, were significantly greater within microgranulomas compared to compact lymphocytic aggregates. Lymphocyte stimulation indices in response to BeSO4 in vitro were not positive in blood, spleen, or tracheobronchial lymph node samples. Be-specific immune responses and nonspecific inflammatory responses to toxic and foreign-body properties of Be may have contributed to the histopathology in both strains of mice. The interstitial mononuclear cell infiltrates, presence of microgranulomas, multinucleated foreign-body and Langhans' giant cells, interstitial fibrosis, and CD4+ T-cell predominance with local proliferation are features similar to CBD in humans. The chronic lung disease induced in these mice by inhaled Be can be used to investigate the importance of variables such as dose, exposure pattern, and physicochemical form of Be in producing this disease.

Animal models of beryllium-induced lung disease

The inhalation Toxicology Research Institute (ITRI) is conducting research to improve the understanding of chronic beryllium disease (CBD) and beryllium-induced lung cancer. Initial animal studies examined beagle dogs that inhaled BeO calcined at either 500 or 1000 degrees C. At similar lung burdens, the 500 degrees C BeO induced more severe and extensive granulomatous pneumonia, lymphocytic infiltration into the lung, and positive Be-specific lymphocyte proliferative responses in vitro than the 1000 degrees C BeO. However, the progressive nature of human CBD was not duplicated. More recently, Strains A/J and C3H/Hej mice were exposed to Be metal by inhalation. This produced a marked granulomatous pneumonia, diffuse infiltrates, and multifocal aggregates of interstitial lymphocytes with a pronounced T helper component and pulmonary in situ lymphocyte proliferation. With respect to lung cancer, at a mean lung burden as low as 17 micrograms Be/g lung, inhaled Be metal induced benign and/or malignant lung tumors in over 50% of male and female F344 rats surviving > or = 1 year on study. Substantial tumor multiplicity was found, but K-ras and p53 gene mutations were virtually absent. In mice, however, a lung burden of approximately 60 micrograms (-300 micrograms Be/g lung) caused only a slight increase in crude lung tumor incidence and multiplicity over controls in strain A/J mice and no elevated incidence in strain C3H mice. Taken together, this research program constitutes a coordinated effort to understand beryllium-induced lung disease in experimental animal models.

The comparative pulmonary toxicity of beryllium metal and beryllium oxide in cynomolgus monkeys

Inhalation of beryllium (Be) may result in an immune-mediated, chronic granulomatous pulmonary disorder known as chronic beryllium disease (CBD). The physicochemical form of Be may affect the incidence and severity of CBD. We exposed cynomolgus monkeys, by bronchoscopic, intrabronchiolar instillation, to either beryllium oxide (BeO; heat-treated at 500 degrees C) or Be metal at concentrations selected to achieve equimolar concentrations of available Be2+ ions dissolving from the particles. Monkeys underwent bronchoalveolar lavage of the right and left diaphragmatic lobes at 14, 30, 60, 90, and 120 days post exposure (dpe). Monkeys were sacrificed at 80 and 180 dpe for evaluation of histopathological pulmonary changes. Numbers of lymphocytes from lung lobes of Be metal-exposed, but not BeO-exposed, monkeys were increased at 14, 30 and 90 dpe. Lung lymphocytes were increased for BeO exposed monkeys only at 60 dpe. In vitro, Be-specific, lung lymphocyte proliferation occurred at 14, 60, and 90 dpe for lymphocytes from Be metal-exposed lung lobes only. At no time were values from BeO-exposed lung lobes different from values from control lobes. Lung lesions in Be metal-exposed monkeys were characterized by focally intense, interstitial fibrosis, marked Type II cell hyperplasia, and variable lymphocyte infiltration. Some Be-metal-exposed monkeys had discrete immune granulomas consisting of tightly organized lymphocytic cuffs surrounding nodular aggregates of epithelioid macrophages. Lesions were rarely present in BeO-exposed monkeys and were much less severe. These data suggest that Be metal produces more severe pulmonary lesions than does BeO and that these lesions are accompanied by Be-specific immune responses.

A microspray nozzle for local administration of liquids or suspensions to lung airways via bronchoscopy

A microspray nozzle has been developed for the localized administration of solutions or suspensions to discrete pulmonary airway regions via bronchoscopy. Toxicants or tracer particles can be administered to single or multiple, specific lung airway segments. This permits studies of local-airway, whole-lung, and systemic responses to inhaled materials. The nozzle is fabricated by ultra-precision machining, has an overall length of 1 mm, and a diameter small enough to fit in the end of a 1.1-mm inner diameter, 1.2-mm outer diameter catheter. In vitro studies demonstrated the delivery efficiency for 99mTc solutions (98 +/- 1% SD) and for suspensions of 99mTc sulfur colloid or 3-mum 85Sr-labeled microspheres (55 +/- 15%). Photographic and gamma camera images of material deposited in the airways of Beagle dogs demonstrated in vivo that the deposition patterns are compact and uniform. The technique may also have therapeutic medical applications.

Disposition of polycyclic aromatic hydrocarbons in the respiratory tract of the beagle dog. I. The alveolar region

Clearance of polycyclic aromatic hydrocarbons (PAHs) from the respiratory tract follows a biphasic pattern, with a rapid clearance of most of the PAH followed by a slow clearance of a small fraction. In previously published models, it was predicted that the rapid phase represents clearance through the thin epithelial barriers in the alveoli, the slow clearance is through the thicker epithelium of the airways, and the rate of clearance from either region will be slowed if the PAH has a high degree of lipophilicity. The objective of this first study in a series of three was to validate model predictions for rates of alveolar clearance of PAHs of different lipophilicities. A new method was developed to expose dogs to a bolus of aerosolized crystals of either benzo[a]pyrene (BaP) or phenanthrene (Phe) in a single breath. A bolus of PAH crystals was formed by condensation from a heated vapor and was injected into the pulmonary region. The bloodborne clearance of the PAHs was monitored by repeatedly sampling blood through catheters in the ascending aorta and the right atrium of the dog. Half of the Phe and the BaP cleared within 1 min and 2.4 min, respectively. The data indicated that the clearance of the highly lipophilic BaP was limited by diffusion of the PAH through the alveolar septa, while clearance of the moderately lipophilic Phe was limited mostly by the rate of perfusion of the blood. The results indicate that inhaled PAHs of sufficient lipophilicity to limit diffusion through cells have a greater potential for toxicity to the lung than less lipophilic PAHs. Because of thicker epithelia, bronchi should be at greater risk than the alveoli for PAH-induced toxicity exerted at the portal of entry.

Disposition of polycyclic aromatic hydrocarbons in the respiratory tract of the beagle dog. II. The conducting airways

Physiological models have predicted that the lipophilicity of solutes such as polycyclic aromatic hydrocarbons (PAHs) will delay clearance from the respiratory tract. This clearance consists of a delayed penetration of the mucous lining layer (MLL), allowing mucociliary clearance, followed by a slow penetration of PAHs through walls of the conducting airways. To test this prediction, mucociliary clearance and retention in the mucosa of PAHs deposited in the conducting airways of the Beagle dog were measured. Mucociliary clearance of particles and dissolved PAHs was measured by instilling onto the MLL in a main stem bronchus or the distal trachea small volume of saline containing either dissolved benzo(a)pyrene (BaP) or phenanthrene (Phe), or a suspension of particulate solvent green (SG) or macroaggregated albumin (MAA). Sequential lavage of the mucous-retained materials followed the instillations. Retention of BaP in the airway walls of the bronchial tree was studied by instilling the hydrocarbon in an ethanol/saline solution at precise locations of the upper bronchial tree, and measuring the concentration of BaP and its major metabolites in the tissues. Results indicated that mucociliary clearance of SG and MAA particles in the trachea of the Beagle dog occurred at average rates of 27-30 mm/min. Of the two solutes, only the highly lipophilic BaP was sufficiently retained within the MLL to be transported with the mucociliary escalator. In addition, a fraction of the lipophilic materials cleared at a very rapid rate, in excess of 90 mm/min. This may indicate that one monolayer of pulmonary surfactant at the air interface is spreading out of the lungs on top of the MLL ata faster rate than mucociliary clearance. However, despite the protective properties of the MLL, fractions of BaP penetrating to the bronchial epithelium had a clearance half-time in the range of 1.4 hr, a period during which considerable metabolism of the PAH occurred. This long retention indicates a diffusion-limited uptake of BaP by the airways, and underscores the potential for local toxicity of highly lipophilic toxicants in the bronchial epithelium.

Sequential analysis of the pathogenesis of plutonium-induced pulmonary neoplasms in the rat: morphology, morphometry, and cytokinetics

Light microscopy, morphometry, and cytokinetic techniques were used to examine the dynamics of plutonium-induced pulmonary proliferative lesions and neoplasms in rats at several intervals to 450 days after inhalation exposure to aerosols of 239PuO2. Maximal increases in alveolar and bronchiolar epithelial cell labeling were seen at 30 days; decreasing subsequently, the levels remained elevated above control indices. Focal proliferative epithelial lesions developed in the lung by 180 days and before the onset of pulmonary neoplasms. Pulmonary neoplasms, predominantly adenocarcinomas and squamous cell carcinomas, were initially observed at 308 days. The proliferative lesions progressed through a succession of morphological changes leading to the development of neoplasms. The volume density (fraction) and epithelial surface area of foci of alveolar epithelial hyperplasia increased progressively between 180 and 450 days after exposure, in contrast to the other proliferative lesions. We conclude that plutonium-induced pulmonary neoplasms develop through a succession of focal proliferative lesions that represent developmental preneoplastic lesions. Progressive increases in volume and epithelial surface area of the alveolar epithelial hyperplasias suggest that they may be more at risk for neoplastic transformation than the other histological types of proliferative foci.

Species differences in urinary butadiene metabolites; identification of 1,2-dihydroxy-4-(N-acetylcysteinyl)butane, a novel metabolite of butadiene

1,3-Butadiene (BD) is used in the manufacture of styrene-BD and polybutadiene rubber. Differences seen in chronic toxicity studies in the susceptibility of B6C3F1 mice and Sprague-Dawley rats to BD raise the question of how to use the rodent toxicology data to predict the health risk of BD in humans. The purpose of this study was to determine if there are species differences in the metabolism of BD to urinary metabolites that might help to explain the differences in the toxicity of BD. The major urinary metabolites of BD in F344/N rats, Sprague-Dawley rats, B6C3F1 mice, Syrian hamsters, and cynomolgus monkeys were identified as 1,2-dihydroxy-4-(N-acetylcysteinyl)-butane (I) and the N-acetylcysteine conjugate of BD monoxide [1-hydroxy-2-(N-acetylcysteinyl)-3-butene] (II). These mercapturic acids are formed by addition of glutathione at either the double bond (I) or the epoxide (II) respectively. When exposed to approximately 8000 p.p.m. of BD for 2 h, the mice excreted 3-4 times as much metabolite II as I, the hamster and the rats produced approximately 1.5 times as much metabolite II as I, while the monkeys produced primarily metabolite I. The ratio of formation of metabolite I to the total formation of the two mercapturic acids correlated well with the known hepatic epoxide hydrolase activity in the different species. These data suggest that (i) the availability of the monoepoxide for conjugation with glutathione is highest in the mouse, followed by the hamster and the rat, and is lowest in the monkey; and (ii) the epoxide availability is inversely related to the hepatic activity of epoxide hydrolase, the enzyme that removes the epoxide by hydrolysis. The ratio of the two mercapturic acids in human urine following BD exposure may indicate the pathways of BD metabolism in humans and may aid in the determination of the most appropriate animal model for BD toxicity.

In vitro activity of silicon carbide whiskers in comparison to other industrial fibers using four cell culture systems

Silicon carbide whiskers (SiCW) and continuous glass filaments are important components of composite materials having potentially widespread use in the automotive, aerospace, and power generation industries. We determined the in vitro activity of three well-characterized samples of silicon carbide whiskers and a continuous glass filament sample in four different cellular assays and compared this to the activities of UICC crocidolite, JM Code 100 glass microfiber, and erionite in the same assay systems. The SiCW had a diameter range of 0.32-0.75 microns and a length range of 4.5-20.1 microns. The SiCW was significantly toxic; on a mass basis, one SiCW sample was more toxic than crocidolite; however, JM Code 100 glass microfiber, which is not toxic in vivo (i.e., it does not cause fibrogenesis or carcinogenesis when inhaled), was also more toxic than crocidolite. The glass filament sample was the least cytotoxic of all the samples tested. On a fiber number basis, all three SiCW samples were more toxic than crocidolite. The results of our study showed that SiCW exhibits significant in vitro biological reactivity. Thus, despite the caution that must be exercised in extrpolating the results of in vitro studies to conclusions about in vivo health effects, SiCW should be considered toxic until further toxicological data are available.

Dosimetry of beryllium in cultured canine pulmonary alveolar macrophages

This study was designed to determine the dosimetry within macrophages of beryllium compounds administered at sublethal doses. Information on the dosimetry of beryllium within macrophages is required to guide further efforts to isolate and characterize beryllium-containing haptens. Inhalation of beryllium aerosols can cause chronic berylliosis, a progressive, granulomatous fibrosis of the lung. Studies in laboratory animals indicate that alveolar macrophages take up beryllium compounds and participate in a hypersensitivity immune response to beryllium-containing antigen. Beagle dog macrophage cultures were incubated with 7BeSO4 in solution or with suspensions of 7BeO particles that had been calcined at 500 or 1000 degrees C. Beryllium-7 was measured in fractions collected from cultures after successive centrifugation and filtration steps at 2, 6, 20, and 48 h after addition. An insignificant percentage of BeSO4 was taken up by the cells and did not cause cytotoxicity. Maximum BeO uptake occurred within 6 h, was 60 +/- 6% of added BeO, and was independent of BeO calcination temperature or specific surface area. Approximately 22% of 500 degrees C BeO dissolved within 48 h after addition to cell culture, concurrent with 39% cell killing. Dissolved beryllium remained associated with cells until a cytotoxic concentration was reached (2.2 x 10(-5) M, 15 nmol Be/10(6) cells), when the beryllium was released into the medium. There was no significant dissolution of the 1000 degrees C BeO within 48 h, and no significant cell killing. The results indicate that beryllium dissolved from phagocytized BeO was more cytotoxic than soluble beryllium added extracellularly. The data support an interactive mechanism in which phagocytized BeO particles were dissolved, and dissolved beryllium remained associated with the macrophage until a cytotoxic concentration accumulated, whereupon the beryllium was released to the medium and not appreciably taken up by viable cells.

Effects of beryllium metal particles on the viability and function of cultured rat alveolar macrophages

The physicochemical properties of particles influence their in vivo toxicity following deposition in the respiratory tract. To evaluate the relative contributions of mass and surface area to particle-induced toxicity, rat pulmonary alveolar macrophages (PAM) were exposed to four types of particles in vitro. We used three beryllium metal samples: relatively large (Be-II) and relatively small (Be-V) sized fractions of beryllium metal obtained from an aerosol cyclone, and a beryllium metal aerosol generated by laser vaporization of bulk beryllium metal in an argon atmosphere (Be-L). We also used glass beads (GB) as a negative control particle. End points examined included cell viability, determined by trypan blue dye exclusion, and changes in phagocytic ability, measured by counting the number of sheep red blood cells internalized by the PAM. Phagocytic ability was inhibited by exposure to beryllium particles at concentrations that did not cause appreciable cell death. Results describing effects based on the mass concentration of particles in culture medium were transformed by the amount of specific surface area of the particles to permit the expression of toxicity relative to the amount of particle surface per unit volume of culture medium. On a mass basis, the order of particle-related cytotoxicity was Be-L greater than Be-V greater than Be-II greater than GB, and for inhibition of phagocytosis, the order was Be-L approximately Be-V greater than Be-II greater than GB. When analyzed on a specific surface area basis, the cytotoxicity of the different materials became more similar in a fashion that was largely predicted by the amount of surface of the particles administered. However, because differences in specific surface area among the beryllium particle samples did not entirely predict cytotoxicity, we concluded that factors in addition to specific surface area influenced the expression of toxic effects in cultures of PAM exposed to beryllium metal.

The acute toxicity of inhaled beryllium metal in rats

We exposed rats once by nose only for 50 min to a mean concentration of 800 micrograms/m3 of beryllium metal (initial lung burden, 625 micrograms) to characterize the acute toxic effects within the lung. Histological changes within the lung and enzyme changes within bronchoalveolar lavage (BAL) fluid were evaluated at 3, 7, 10, 14, 31, 59, 115, and 171 days postexposure (dpe). Beryllium metal-exposed rats developed acute, necrotizing, hemorrhagic, exudative pneumonitis and intraalveolar fibrosis that peaked at 14 dpe. By 31 dpe, inflammatory lesions were replaced by minimal interstitial and intraalveolar fibrosis. Necrotizing inflammation was observed again at 59 dpe which progressed to chronic-active inflammation by 115 dpe. This inflammation worsened progressively, as did alveolar macrophage and epithelial hyperplasia, becoming severe at 171 dpe. Low numbers of diffusely distributed lymphocytes were also present but they were not associated with granulomas as is observed in beryllium-induced disease in man. Throughout the experiment, total numbers of cells were elevated within the BAL samples due primarily to increased numbers of neutrophils. Lymphocytes were not elevated in BAL samples collected from beryllium-exposed rats at any time after exposure. Lactate dehydrogenase (LDH), beta-glucuronidase, and protein levels were elevated in BAL fluid from 3 through 14 dpe but returned to near normal levels by 31 dpe. LDH increased once again at 59 dpe and remained elevated at 171 dpe. beta-Glucuronidase and protein levels were slightly, but not significantly, elevated from 31 through 171 dpe. Results indicate that inhalation of beryllium metal by rats results in severe, acute chemical pneumonitis that is followed by a quiescent period of minimal inflammation and mild fibrosis. Progressive, chronic-active, fibrosing pneumonitis is observed later. Chronic beryllium lung disease of man is an immunologically mediated granulomatous lung disease, whereas beryllium-induced lung lesions in rats appear to be due to direct chemical toxicity and foreign-body-type reactions.

Relative efficacy of long-acting stimulants on children with attention deficit-hyperactivity disorder: a comparison of standard methylphenidate, sustained-release methylphenidate, sustained-release dextroamphetamine, and pemoline

Twenty-two children with attention deficit-hyperactivity disorder underwent a double-blind, placebo-controlled, crossover evaluation of the efficacy of standard methylphenidate twice a day and comparable doses every morning of a sustained-release preparation of methylphenidate (SR-20 Ritalin), a sustained-release form of dextroamphetamine (Dexedrine Spansule), and pemoline. The children were participating in a summer treatment program in which they engaged in recreational and classroom activities. Dependent measures include evaluations of social behavior during group recreational activities, classroom performance, and performance on a continuous performance task. Results revealed generally equivalent and beneficial effects of all four medications. Dexedrine Spansule and pemoline tended to produce the most consistent effects and were recommended for 10 of the 15 children who were responders to medication. The continuous performance task results showed that all four medications had an effect within 2 hours of ingestion, and the effects lasted for 9 hours. The implications of these results for the use of long-acting stimulant medication in children with attention deficit-hyperactivity disorder are discussed.

Clearance, translocation, and excretion of beryllium following acute inhalation of beryllium oxide by beagle dogs

Beagle dogs inhaled radiolabeled beryllium oxide (7BeO) particles that were calcined at either 500 or 1000 degrees C, resulting in either high (mean of 50 micrograms/kg body wt) or low (mean of 17 micrograms/kg body wt) initial lung burdens (ILBs) of both preparations of BeO. Levels of beryllium in whole body, tissue, and excreta were measured by external gamma-ray counting. Dogs were euthanized in pairs at 8, 32, 64, and 180 days after exposure to determine beryllium distribution in tissues. Beryllium oxide calcined at 1000 degrees C was retained more tenaciously in the lungs (62% of the ILB retained at 180 days after exposure) than BeO calcined at 500 degrees C (14% of the ILB retained at 180 days after exposure). Most of the beryllium that was cleared from the lungs and not excreted was translocated to the tracheobronchial lymph nodes, skeleton, liver, and blood. More beryllium was translocated to the skeleton and liver at 180 days after inhalation of BeO prepared at 500 degrees C than at 1000 degrees C. The predominant mode of excretion at early times after exposure was through the feces, with urinary excretion assuming predominance at later times. These data are important for interpreting the toxic effects of beryllium in the exposed dogs. Furthermore, because little is known concerning the retention and clearance of inhaled beryllium in man, these results provide information that may be used to understand the disposition of beryllium in accidentally exposed humans.

Compartmental modeling of the long-term retention of insoluble particles deposited in the alveolar region of the lung

The state of the art for modeling the retention of inhaled insoluble particles deposited in the alveolar region of the lung is briefly reviewed, and a new compartmental model of long-term retention is proposed. Wherever possible, this new model favors the replacement of simple first-order kinetics of particle transport processes in the lung by quantified mechanisms derived from or suggested by experimental data of published studies in lung physiology and histopathology. In particular, all macrophage-mediated transport processes, including classical alveolar clearance onto the mucociliary escalator, are modeled as dependent on actual macrophage mobility and are assumed to be influenced by the finite macrophage life time. The mobility is predicted to decrease with increasing particle burden of the macrophage, and there is a limit to the macrophage capacity for accumulating burdens of insoluble particles by phagocytosis. Furthermore, at high particle burdens, macrophages will be progressivity sequestered by irreversible aggregation and immobilization. Using published data on Fischer 344 rats for a quantitative demonstration of the patterns of the new model under chronic exposures, a basic set of model parameters predicts that, at moderate particle deposition rates, retention is limiting itself by establishing a steady state, and the alveolar burden is almost completely eliminated during the postexposure period. However, at high particle deposition rates, the alveolar particle burden increases continuously during the exposure period, and only a small fraction of the deposit is subject to clearance after termination of exposure. In qualitative terms, these are typical features of the "overload" effect which has been observed in a number of recent chronic aerosol inhalation exposure studies with animals.

Determination of the oxide layer thickness on beryllium metal particles

The hypothesis was tested that beryllium metal particles have a uniformly thick surface coating of beryllium oxide and that smaller particles should have a higher oxide fraction by mass because they have a higher surface to volume ratio. The mass fraction of oxygen, physical density, and specific surface area were determined for size-fractionated samples of respirable beryllium metal particles. The largest particles analyzed (count median diameter 4.6 microns with geometric standard deviation 1.6) contained 7% +/- 1% beryllium oxide by mass; had a physical density of 1.90 +/- 0.02 g/cm3; and had a specific surface area of 4.0 +/- 0.3 m2/g. The smallest particles analyzed (count median diameter 0.4 micron with geometric standard deviation 1.8) contained 31% +/- 3% beryllium oxide by mass; had a physical density of 2.00 +/- 0.17 g/cm3; and had a specific surface area of 20.8 +/- 2.1 m2/g. These shifts in density and oxide content with size and surface area are consistent with a beryllium metal core of density 1.84 +/- 0.02 g/cm3 (1.848 g/cm3 is theoretical); a beryllium oxide layer of density of 2.53 +/- 0.16 g/cm3 (3.025 g/cm3 is the perfect crystalline density); and an oxide layer thickness of 49 +/- 4 A for all particle sizes. These results indicate that the inhalation toxicity of beryllium metal particles may be similar to that of beryllium oxide formed at low temperatures.

A canine model of beryllium-induced granulomatous lung disease

Groups of beagle dogs were exposed by inhalation to attain either low or high initial lung burdens (ILB) of BeO calcined at 500 degrees or 1000 degrees C. Dogs were killed at 8, 32, 64, 180, and 365 days after exposure for evaluation of beryllium tissue burdens and histopathologic examination. Histologic lesions were characterized by perivascular and peribronchiolar infiltrates of lymphocytes and macrophages 8 days after exposure. These lesions progressed to distinct microgranulomas accompanied by patchy granulomatous pneumonia. Lesions were more severe in dogs exposed to 500 degrees C BeO. Additional dogs were sampled by bronchoalveolar lavage at 3, 6, 7, 11, 15, 18, and 22 months after exposure for characterization of lung cytology and lung immune responses. Lymphocyte percentages and numbers were increased in lavage samples 3 months after exposure in dogs with both the high and low ILB of 500 degrees C. Values for both parameters decreased rapidly thereafter. Dogs with either low or high ILB of 1000 degrees C-treated BeO displayed negligible to low and variable changes in both lymphocyte percentages and numbers. In vitro lymphocyte stimulation by beryllium was increased 180 and 210 days after exposure in dogs with the high ILB 500 degrees C BeO only. A marked degree of individual variation in both histologic lesions and lymphocyte responses among dogs was noted. Less soluble 1000 degrees C-treated BeO was retained in the lung longer than the more soluble 500 degrees C-treated material that was cleared almost entirely by 1 year after exposure. Because these changes are similar to those reported in humans with chronic beryllium disease, these data suggest that the beagle represents a good model to study histologic and immunologic aspects of this disease syndrome.

The effect of beryllium compound solubility on in vitro canine alveolar macrophage cytotoxicity

Pulmonary alveolar macrophage cells (PAM), obtained by bronchopulmonary lavage of Beagle dogs, were exposed in vitro to beryllium oxide (BeO) particles calcined at either 500 or 1000 degrees C or to beryllium sulfate (BeSO4). Cell viability was determined by trypan blue dye exclusion after 20 h in culture. The most toxic material tested was BeSO4, followed by BeO calcined at 500 degrees C, then BeO calcined at 1000 degrees C. An in vitro dissolution technique was used to measure the relative solubility of the BeO particles. The BeO prepared at 500 degrees C exhibited greater solubility compared with BeO prepared at 1000 degrees C. This study extends previous work by examining the effects of beryllium compounds on canine PAM, and by relating PAM cytotoxicity with measured values of beryllium compound solubility.