In this paper, we review epidemiological studies on the relationship between neighborhood asbestos exposure and risk of asbestos-related diseases. In other countries, several studies found that the risk of developing mesothelioma increased among the residents who lived near asbestos manufacturing plants in the U.K., U.S.A. and Italy and an asbestos mine in Australia. In Japan, some studies suggest that the risk of developing mesothelioma increased among the residents who lived near plants of two major asbestos companies. We also report the researches on the residents who lived near many small-scale asbestos plants.
It has been established that asbestos is associated with asbestosis (pneumoconiosis) , lung cancer and mesothelioma. These health effects are characterized by the following factors: (1) because of the long latency period between exposure and onset of extrinsic malignant neoplasms, the need for earlier preventative measures were left unrecognized; (2) malignant mesothelioma can be developed following exposure at environmental levels; (3) lung cancer is a major malignant neoplasm in which other factors are involved and there is evidence to suggest that the two factors of asbestos exposure and cigarette smoking are synergistic. Japan has been criticized for being slow to take action, however, it is true, in general, that the status quo of each country is taken into consideration in the application of scientific findings. In retrospect it can be said that there was no validity of the continued use of asbestos in the late 1980s in Japan in terms of its economic status and technological level at that time. It was also a lesson in creating a mechanism to apply scientific findings to society and determining how the human factor is to be dealt with. The Japan Association of Aerosol Science and Technology will bear responsibility in promoting the spread of information to society when hazardous health effects of new particulate matter are discussed. The following principles included in EU policy are thought to follow: (1) precautionary principle; (2) prevention principle; (3) ratification at source principle; and (4) polluter pays indemnity principle.
It is well known that asbestos induced pulmonary inflammation result in fibrosis. Oxidative stress is thought to be one of the pathogenesis of pulmonary fibrosis, and Heme Oxygenase-1 (HO-1) has been linked to process of protecting lung tissue against oxidative stress. Heme Oxygenase-1 (HO-1) inducible enzyme that catalyzes heme to generate bilirubin, ferritin, and carbon monoxide (CO) and these resolved products immediately protect lung tissue against oxidative stress. To determine whether or not HO-1 can act as a biomarker of lung injury induced by materials, we made serial measurements of HO-1 expression in rat lungs following the intratracheal instillation of several materials (crocidolite, chrysotile, amosite, crystalline silica) . Male Wistar rats were administered 1 mg or 2 mg of materials suspended in saline by a single intratrachally and were sacrificed at 3 days, 1 week, 1 month, 3 months and 6 months of recovery time. The expression of HO-1 in the rat lung was observed by western blot or ELISA analysis. In case of crocidolite, amosite, chrysotile and crystalline silica which cause sever injury, protein levels of HO-1 in the rat lung constantly increased during the recovery time. The pattern of HO-1 expression is different from materials with severe lung injury and mild or moderate lung injury. It suggests that HO-1 can act as a biomarker of lung injury exposed to particles and fibrous materials.
The Ministry of Health, Labour and Welfare issued the “Ordinance on Prevention of Hazards Due to Asbestos” on July 1, 2005, under Industrial Safety and Health Law. This was regulated by the outlook that demolition of buildings sprayed or using asbestos would increase until the middle of the 21 century in Japan and to prevent asbestos exposure of the demolition workers. About the same time, an ex-asbestos company in Amagasaki, Japan disclosed that some residents who lived near the asbestos factory contracted mesothelioma. Consequently the asbestos problem, which had been considered as only workers' problem until then, quickly became a social problem in Japan. The ex-asbestos factory had produced cement water pipes using crocidolite for 20 years from 1955 to 1975. In those days there were no severe regulations to control asbestos use, therefore, it is conceivable that the working environment was very poor. After 30 to 50 years, asbestos-related diseases such as mesothelioma and lung cancer appeared. The counter-measures for this asbestos disaster has taken action in every government and organization. The use of asbestos was totally banned in September, 2005, except a few materials which could not be replaced by other materials at the present. The definition of asbestos products is also regulated as “the materials including 0.1 weight % or more of asbestos”. This was applied to natural minerals including asbestos as well. Accordingly measurement method is required to quantify asbestos in products or minerals at the level of 0.1 weight % . At the present X-ray diffraction (XRD) method and phase contrast microscopy using dispersion staining method are used as the certification method for constructing materials and other industrial products. For natural minerals XRD method is effective. This paper introduces some measurement methods of asbestos in air and in bulk materials.
Inertial impactors classify particles according to their aerodynamic diameter for the measurement of particle size distribution. When using inertial impactors, bounce-off, re-entrainment, and break up of particles upon the particle collision onto the impaction plate are inevitable problems. In this study, we investigated the effectiveness of rubber sheets to suppress particles bounce-off. We measured the adhesion efficiency of various rubbers by changing the particle diameter, impaction velocity and the temperature of rubber sheet. The adhesion efficiency of particles increases with impaction velocity when a rubber with a lower glass transition temperature was used as the impaction substrate. Furthermore, the particle bounce-off can be controlled for various kinds of rubber sheets by adjusting the temperature of rubber sheets.
Generation and deposition of dust particles in plasma processes for thin film preparation often causes serious problems leading to yield reduction. A device capable of conveniently measuring the properties of particles suspended in plasma has therefore been needed. In the present work, a compact particle monitoring device based on light scattering is developed, and its performance is examined. This device irradiates suspended particles with laser light consisting of two different wavelengths, and determines the particle diameter from the intensity of scattered light. Preliminary experiments using monodisperse latex particles dispersed in water indicated that the relationship between the scattered light intensity and particle diameter was consistent with that predicted by the light scattering theory. The device was then applied to a plasma enhanced CVD chamber in which SiH4/H2 plasma is formed to fabricate Si thin film. As a result, particles generated and suspended in the plasma could be detected when the amount of particles were sufficient depending on particle size. The particle size determined by the monitoring device was in the range between 0.2 and 0.3 μm. This size was in satisfactory agreement with the size of the particles deposited on the film.
In the ocean, iron in a soluble form acts as a micronutrient for oceanic phytoplankton. Mineral dust deposition to the ocean may be a significant source of iron that is typically insoluble. It is required to understand the atmospheric processes that convert insoluble iron to soluble forms. We focused attention on Fe-leaching from hematite particles when they come into direct contact with sulfuric acid aerosols, and performed laboratory experiments to determine their dissolved fraction to ferric ion and the temperature dependence of the dissolution rate. Hematite particles ranging from 2.1 to 3.3 μm in aerodynamic diameter were prepared using a nebulizer combined with classification by a cascade impactor, and sulfuric aerosols (0.5 μm, pH 0) were generated with an ultrasonic nebulizer. Reactions between the hematite particles and the sulfuric acid mists were conducted at 40 % R.H. under 15-25 °C over a range of reaction time from 24 hr to 72 hr. Hematite dissolution was accelerated with an increase of reaction temperature and the dissolved fraction was 0.82 % at 15 °C after 72 hr reaction, which was comparable to the previous theoretical estimates. We also determined the temperature dependence of the dissolution rate, and derived the Arrhenius rate equations.