Nanoparticles have new chemical, electrical, optical and magnetic properties with different respondences to external stimuli (light, heat, voltage), compared to larger particles. Since nanoparticles will be applied in a variety of industrial fields such as chemistry, electronics, cosmetics, medicine, food, and environmental technology, the possibility of exposure to these nanoparticles in the workplace might increase. In the atmospheric environment, increase in nanoparticle concentration is reported in the roadside area during rush hour. There is a possibility of exposure to the ambient nanoparticles. Diesel engines release a large number of nanoparticles. However, little has been done on the exposure assessment and health and environmental risk assessment of both manufactured and ambient nanoparticles. In this paper, 1) results of the previous studies on the health effects of diesel particles are summarized, 2) behavior and translocation of nanoparticles in the human body are discussed using the previous toxicological and epidemiological studies on nanoparticles and the research issues on the health effect of nanoparticles in diesel exhaust are presented, 3) newly fabricated facilities for assessing health and environmental risk and our plan to investigate health risk assessment of nanoparticles using the facilities are introduced.
Nanoscience and nanotechnology are remarkably developed. However, some reports suggest that nanoparticle influence not only the cardiopulmonary system but also the cranial nerves via the olfactory bulb and are also absorbed through skin. Currently, nanoparticles are used in some sunscreen, cosmetic and catalytic products, which release nanoparticles into the environment and exposure to workers in manufactured nanoparticles. Therefore, appropriate risk assessment and risk management are required. This section describes the characteristics and health effects of fullerene and carbon nanotubes. The sphere of fullerene is similar to quartz, carbon particles or titanium dioxide, while carbon nanotubes are similar to asbestos. These nanoproducts seem to be closely related to their toxicity in the human body.
Pulmonary effects of titanium dioxide, crystalline silica, and nickel oxide were reviewed focusing on the relevance of the particle size. For titanium dioxide and nickel oxide, ultrafine particles administered to the lung causes greater inflammatory response than larger particles on the basis of unit mass. Surface properties (surface chemistry) appear to play an important role in ultrafine toxicity of titanium dioxide. There are few reports that show the submicron-sized (ultrafine) crystalline silica administered to the lung has a greater toxic potential than larger silica, however, further study is needed to confirm the cytotoxicity.
This paper presents the biological effects of rare earth elements (REEs) on respiratory organs investigated by the research groups of National Institute of Industrial Health and others. REEs are such important components of current industry that the elucidation of the biological effects and environmental effects is a matter of course. In our study, animal experiments have been carried out employing both of intratracheal administration and inhalation exposure into rats for the sample materials: Y2O3, La2O3, Nd2O3, CeO2, and Sm2O3, in which CeO2 included two kinds of samples of different particle sizes. The acute toxicity of rare earth oxides was weak, but the pulmonary effects continued for a long time. The typical changes of lung tissues were pathologically observed as pulmonary alveolar proteinosis, granuloma and pulmonary fibrosis. The rats to which were injected CeO2 of coarse particle did not show any pulmonary lesion, but those of fine particles showed lung lesion at the same level as the other rare earth oxides. As a conclusion, subchronical pulmonary effects from rare earth oxides was observed to respiratory organs although it did not cause serious acute toxicity. Therefore, countermeasures, such as wearing respiratory mask, would be basically necessary for the dust workers using REEs.
There was little information regarding the adverse health effects to humans or animals arising from exposure to indium compounds until mid 1990. However, due to the increasingly frequent industrial use of indium such as indium-tin oxide (ITO), the potential occupational or environmental exposure to indium compounds has attracted much attention. In 2001, the first case of interstitial pneumonia caused by exposure to ITO occupationally was reported. Recent animal studies have indicated the pulmonary or testicular toxicity of indium compounds. Furthermore, carcinogenicity of InP was demonstrated by the inhalation study in rats and mice and that of InAs was suspected in the intratracheal instillation study using hamsters. It appeared that indium was toxic when released from the particles, though the physical characteristics of the particles also contribute to toxic effect. It is necessary to pay much greater attention to the human exposure of indium, indium compounds or ITO.
In a cleanroom for manufacturing semiconductor, flat panel display, and hard disk drive, the contamination control of airborne molecular contaminants is of critical importance. One of the contamination control technologies for gaseous contaminants is chemical air filter. The purpose of this work is to study the monitoring of the chemical air filter life using quartz crystal microbalance (QCM) method. When a chemical air filter is in the early stages of adsorption, the QCM monitoring system used in this study could detect the differences in the concentration of total organic compounds at the inlet and outlet of the chemical air filter. The QCM monitoring system was found to be useful for evaluating the performance of chemical air filters in the prevention of surface contamination. The system could also detect the daily changes in the removal efficiency of high-boiling-point compounds by chemical air filters.
We developed a new method for detecting Kosa (Asian dust) days from the suspended particulate matter (SPM) concentrations measured at seven air-quality monitoring stations in western Japan. When the frequency curve of the horary SPM concentration monitored at each station from January to May showed a bimodal distribution, we assigned a threshold value to extract the distribution of higher concentration. When the days with high SPM concentration were in agreement over a wide area, we defined them as SPM Kosa days. There were 101 SPM Kosa days from 1993 to 2001. Through the analysis of the distribution of atmospheric pressure and the back trajectory analysis, we confirmed that the present method was able to detect 100 Kosa days out of 101, including the Kosa days which were not detected visually because of its weak event. There were 20 SPM Kosa days in 1999, which was the maximum number of Kosa days observed during 1993-2001.
A new type of plasma modulation is proposed to suppress dust particle contamination in a thin-film fabrication process using a radio frequency plasma enhanced CVD reactor. The performance of the modulation, sine-wave modulation, in reducing dust particle generation and deposition is studied experimentally for an a-Si film fabrication process using SiH4/H2. The sine-wave modulation realizes a drastic reduction of the number density and the size of dust particles suspended in plasma, as well as the previously-proposed pulse-wave modulation. However, the sine-wave modulation reduces particle deposition on the films much better than the pulse-wave modulation, owing probably to a better stability of plasma. In addition, the smoothness of the film surfaces is not affected by the plasma modulation. Therefore, the sine-wave modulation is considered to be a useful and practical method to fabricate thin-films with less particle contamination.
Welder's pneumoconiosis, which is caused by the inhalation of welding fumes, is one of the major pneumoconioses in Japan. The major component of welding fumes is iron oxide. Although welder's pneumoconiosis has been considered to be inert, recent reports revealed the possibility of developing fibrosis. In this article, we demonstrate radiological and pathological features of welder's pneumoconiosis, and also review the mechanisms of developing pulmonary fibrosis. In high-resolution CT (HRCT), typical welder's pneumoconiosis shows fine centrilobular nodules in both lung fields. In some cases, fibrotic changes may be seen in subpleural areas in both lower lung fields. Lung biopsy specimens show numerous hemosiderin-laden macrophages within alveolar spaces associated with mild to moderate interstitial fibrosis. The mechanisms of developing fibrosis can be explained by “overload phenomenon”. Namely, in cases of mild exposure to welding fumes, iron oxides and hemosiderin-laden macrophages locate within air-spaces and may be reduced in numbers by mucociliary transport system. However, in cases of massive inhalation, accumulation of iron oxides and hemosiderin-laden macrophages exceed the capacity of mucociliary transport system. As a result, they invade into the interstitium and cause interstitial inflammation or thickening and eventually pulmonary fibrosis.