Characteristics of multiwall carbon nanotubes for an intratracheal instillation study with rats.

Much concern has been raised over the health consequences of workers exposed to carbon nanotubes. In order to characterize multi-wall carbon nanotubes (MWCNT) suspended in a phosphate-buffered saline containing 0.1% Tween 80 for an intratracheal instillation study. Length and width distributions of the MWCNT fibers, dispersion of MWCNT in the suspension and in the lung tissue and the MWCNT contents of metal impurities were investigated. Arithmetic mean length and width of the MWCNT fibers as measured on scanning electron microscope (SEM) photographs were 5.0 microm and 88 nm, respectively, and fibers longer than 5.0 microm were 38.9% of all fibers measured. Dynamic light scattering size measurement revealed that 5-min ultrasonication, together with addition of Tween 80 into the suspension, decreased the hydrodynamic diameters of the agglomerated MWCNT to those of finer particles below 1.0 microm. SEM observation showed good dispersion of MWCNT in the suspension, and in the alveoli on Day 1 after instillation. Concentration of iron, chromium and nickel in the MWCNT were 4,400, 48 and 17 ppm (wt/wt), respectively, all of which were below levels that would elicit positive pulmonary toxic responses to these metals. The results suggest that well-dispersed, long and thin MWCNT fibers exhibit asbestos-like pathogenicity in the lung.

[Airborne particles in a multi-wall carbon nanotube production plant: observation of particle emission and personal exposure 1: Measurement in the packing process].

OBJECTIVES: In order to assess the exposure risks of multiwall carbon nanotubes (MWCNT) for packing workers, we carried out real-time monitoring in the two types of packing facilities of MWCNT, and exposure measurements for the packing workers. METHODS: In the real-time monitoring, a scanning mobility particle sizer (SMPS) and an optical particle counter (OPC) were used to measure nanoscale particles and sub-micron/micron scale particles, respectively. A personal sampler with PM 4.0 was used to measure the personal exposures in the packing facilities. RESULTS: One of the packing facilities is manually operated and the other is automated. The concentrations of airborne dust in both facilities were almost the same as each other at 0.24 mg/m(3) (total dust). However, the results of personal exposure measurements were quite different between the two facilities. The exposure concentrations of workers in the manually and automated operations were 2.39/0.39 (total/respirable) mg/m(3) and 0.29/0.08 (total/respirable) mg/m(3), respectively. From the time series study, submicron scale particles were released into the workplace air when the CNT products were put into temporary container bags from a hopper and manually packed into shipping bags. However, the task-related nanoscale particle release was not observed. CONCLUSIONS: The manual packing operation is one of the "hot spots" in MWCNT production facilities, and automation brings much improvement to reduce MWCNT exposure.

Pulmonary toxicity induced by intratracheal instillation of coarse and fine particles of cerium dioxide in male rats.

In order to examine the short-, medium- and long-term effects of cerium dioxide particles of different sizes on the lung, 10-wk-old male Wistar rats were administered a physiological saline solution with a suspension of coarse or fine particles of cerium dioxide at 34 mg/kg body weight by a single intratracheal instillation. Lungs were examined with cellular and biochemical analyses of the bronchoalveolar lavage (BAL) fluid and histopathology on different days after the instillation. Geometric mean and geometric standard deviation of the diameter were 3.90 microm +/- 1.93 for the coarse (Ce-C) particles, and 0.20 microm +/- 1.20 for the fine (Ce-F) particles. There were no lesions in the lung in the Ce-C-instilled group at any time point after the instillation. The instillation of Ce-F particles primarily induced inflammation, granulomas, mobilization and impairment of alveolar macrophages (AMs), and pulmonary alveolar proteinosis, together with very slight degrees of Type II epithelial cell hyperplasia and of collagen deposition. The pulmonary toxicity of Ce-F-instilled rats was found to be markedly enhanced in sharp contrast to that of Ce-C-instilled rats on the basis of equal mass concentration, suggesting clear dependence of the pulmonary toxicity on numbers and sizes of particles. Causative factors for the pulmonary alveolar proteinosis are discussed with reference to the impaired AMs.

Dissolution of functional materials and rare earth oxides into pseudo alveolar fluid.

The dissolution rates of rare earth oxides and two types of rare earth containing functional materials into water, saline solution, and Gamble's fluid were measured in order to evaluate the biological effects of rare earth-containing functional materials. The tested materials were yttrium, lanthanum, cerium and neodymium oxides, and neodymium-boron-iron magnet alloy (NdBFe) and lanthanum-mish-metal-nickel-cobalt (LmNiCo) hydrogen-containing alloy. The dissolution rates of the rare earth oxides were very low, resulting in concentrations of rare earth elements in the test solutions of the order of ppb. In the most extreme case, Gamble's fluid dissolved 1,400 times more of the rare earth oxides than pure water. Fairly high concentration of neodymium were found in the dissolving fluids, which means that trace neodymium present as an impurity in each rare earth oxide dissolved preferentially. For yttrium oxide, the ratio of neodymium to yttrium that dissolved in the saline solution was greater than 78,000 to 1, taking into account the amount of each that was originally present in the yttrium oxide.

Field evaluation of mercury vapor analytical methods: comparison of the "double amalgam method" and ISO 17733.

In this study, a gold amalgam method called the "Double amalgam method" was compared with the ISO 17733 method for mercury vapor analysis method. In terms of sensitivity and ease of operation, the amalgamation method is superior to the oxidation method. Two parallel samplings were carried out in this research at a button battery factory, where the mercury vapor level in the air was about 0.001 mg/m3 and at a fluorescent lamp factory, where the mercury vapor level was about 0.015 mg/m3. In the both cases, the measured values of the two showed good agreement with each other. As these two workplaces represent typical mercury levels in industries today, the double amalgam method is applicable to working environment measurement.

Effects of surface characteristics of potassium titanate whisker samples on acute lung injury induced by a single intratracheal administration in rats.

We compared in vivo biological effects, focusing on lung inflammatory responses after a single intratracheal administration of two types of well-characterized whiskers: potassium octatitanate and potassium hexatitanate, which have similar fiber sizes and chemical compositions, except their surface morphology. The geometrical mean of length (microm), width (microm), and geometric standard deviation (GSD) are: K(2)Ti(8)O(17) (PT1), 6.0[2.0], 0.35[1.51], having rough surface; K(2)Ti(6)O(13) (PT2), 5.0[2.18], 0.31[1.63], having smooth surface. Sixty male Wistar rats (8 wk old) under anesthesia were injected intratracheally with 2 doses of fibers (0.2 mg/0.5 ml/rat, 1.0 mg/0.5 ml/rat) or the same amount of saline solution (group C). Animals were sacrificed on days 1, 3, and 7 after fiber administration, and then the lung tissue and bronchoalveolar lavage (BAL) were collected. There were no obvious differences among the three groups in the yield of BAL fluid. Total protein concentration in BAL increased significantly from day 1; BAL fucose level increased significantly from day 3 in a dose-dependent manner, which gradually recovered by day 7 in groups PT1 and PT2. BAL total protein and fucose in group PT1 increased significantly compared with those in group PT2 at a dose level of 1.0 mg. A dose-independent increase of beta-glucuronidase activity and decrease of superoxide dismutase activity were observed in both fibers. BAL tumor necrosis factor-alpha (TNF-alpha) increased significantly in animals treated with 1.0 mg dosage of PT1 and PT2 on day 1. However, BAL IL-1beta did not show any marked change during the experimental period in animals treated with both fibers. On day 1, BAL cytokine-induced neutrophil attractants (CINC)/growth-related gene product (GRO) increased significantly in the PT1 group treated with 0.2 and 1.0 mg dosage. On day 3, the group treated with 1.0 mg PT1 showed significant increase of CINC/GRO compared with the group treated with 1.0 mg PT2, which recovered to the control level on day 7. Expression of various chemokine mRNAs (MCP-3, MIP-1alpha, RANTES, and eotaxin) increased in rats treated with PT1 or PT2 on day 1 and/or day 3. Increase of gene expression in the PT1 group was greater than that of the PT2 group at 0.2 mg dosage level. These results suggest that differences in the surface morphology of the whisker fibers of similar length and diameter, density, and chemical composition appear to be related to the facilitation of macrophage phagocytes in the macrophage-derived biological effects in acute lung injury induced by inhaled fibers.

Inflammatory responses and mucus secretion in rats with acute bronchiolitis induced by nickel chloride.

The effects of inhaled particulate matter in the workplace and outdoor environment on sensitive subpopulations are not sufficiently investigated in human and animal models. Thus, animal models for pulmonary diseases are necessary for appropriate risk assessment of toxic materials. We studied biochemical characteristics of an acute inflammatory process induced by inhalation of nickel chloride aerosols in rats. Acute bronchiolitis was induced by inhalation of nickel chloride aerosols for 5 days in Wistar rats according to the method described by Kyono et al. (1999). Deterioration and recovery from inflammatory responses were evaluated by analyzing markers of inflammation in bronchoalveolar lavage (BAL) fluid. Experimental animals were sacrificed during and after the nickel aerosol exposure period. The number of neutrophils markedly increased to approximately 0.5 x 10(3) cells/microl BAL fluid during nickel aerosol exposure, accompanied by increase of total protein, soluble L-selectin, cytokine-induced neutrophil chemoattractant/growth-regulated gene products (CINC/GRO), elastolytic activity, trypsin inhibitory capacity, beta-glucuronidase activity, fucose, and sialic acid in BAL fluid compared with those of the control group. There was correlation between number of leukocytes and soluble L-selectin concentration. The number of pulmonary macrophages in BAL fluid decreased to approximately 15% of those of the control group on the days of nickel aerosol exposure. The level of CINC/GRO recovered to that of the control group on day 3 after cessation of the nickel aerosol exposure. However, other inflammatory markers remained at the elevated levels. Changes in the markers of inflammation during and after the nickel aerosol exposure were consistent with previously reported morphological findings. The results indicated that this animal model is potentially useful as an acute bronchiolitis model.