Durham method has been adopted widely in Japan as the measurement method for counting the number of pollens. However, it is a tedious method for researchers because they have to count the exact number of pollens on plates using a microscope. Therefore the number of pollens has been reported only once a day from most of the observatories. In order to obtain the hourly number of pollens for further researches, automatic pollen counters have been developed.
We evaluated the performance of the pollen counter KP-1000 (Kowa Co. Ltd.), which had been developed by the project of Ministry of Education, Culture, Sports, Science and Technology. In order to evaluate the capability for counting Cedar and Cypress pollen particles, we compared the number of pollens measured by KP-1000 with the number of pollens obtained by Durham method and the number of pollens caught on the outlet filter of KP-1000. Furthermore we compared the number of pollens measured by KP-1000 with the number of pollens counted by another pollen counter KH-3000 (Yamato Mfg. Co. Ltd.). The result of the comparison showed that KP-1000 could distinguish Cedar and Cypress pollens accurately.
We found the high concentration of pollens in early mornings through the hourly observation of Cedar and Cypress pollens during the spring of 2005. By using the Backward Trajectory Method, we found that the high concentration phenomena of pollens were brought by the long distance transportation of pollens from Shizuoka area via Izu Peninsula and Kanagawa to Tokyo.

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In order to estimate the long-term behavior of volcanic gases from Miyake Island and the effect to deposition of sulfate, a numerical simulation for sulfur dioxides by a chemical transport model coupled with a mesoscale meteorological model was conducted for four years. The results of simulation were verified through the comparison with the observed data. The simulation well described the behavior of SO₂ and sulfate, and wet deposition of sulfate reasonably. The simulation indicated that the predominant wind system such as winter and summer monsoon played an important role in the transport of volcanic gases. The volcanic gases from Miyake Island increased the concentrations and depositions of sulfur dioxides in Honshu, the main island of Japan, and the Northwest Pacific. The effect of the eruption of Miyake Island was significant in sulfur dioxide concentration and deposition on the sea where the emissions of pollutants do not exist.

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We describe the development of a global mineral dust transport model and its application to the forecast of Kosa phenomena by Meteorological Research Institute and Japan Meteorological Agency. The model incorporates the dust emission by wind erosion, the advective transport by large-scale circulation, the vertical eddy diffusion by turbulence, the vertical transport by cumulus convection, and the removal by dry and wet deposition processes. Simulations of large-scale Kosa phenomena in March and November 2002 show that the model well reproduced the characteristics of the phenomena. The forecast experiment of Kosa phenomenon on 12 November 2002 demonstrates that the model can forecast the arrival of dust to Japan from 111 hours before, which is even before the occurrence of dust storm in China. Future subjects of Kosa forecast include the consideration of other aerosol species, the incorporation of the present conditions of the dust source regions, the data assimilation of dust distribution, and the refinement in the resolution of the model.

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In order to investigate the characteristics on natural radioactivity of loess, desert sand and eolian dust origin soil distributed in East Asia, analyses for ²³⁸U, ²³²Th and ⁴⁰K concentrations by ICP-MS and ICP-AES, and for major chemical composition, SiO₂, Al₂O₃, K₂O, etc., by XRF have been performed on 48 samples collected from the wide area of China and three prefectures of Japan. The results for loess samples indicated that the concentrations of natural radioactive elements and major chemical composition are almost homogeneous over Chinese Loess Plateau. Also the results suggested that the basic material of the red soils developed on Quaternary limestone in Okinawa prefecture, southwestern part of Japan, is not weathering residual from the base rock, but the eolian dust from the high background radiation area in the southeastern part of China. These observations could give important keys to understand the origin place of the eolian dust in East Asia during the Quaternary.

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Pollution mechanism by Suspended Particulate Matter (SPM, atmospheric aerosols with diameter less than 10 μm) in rainy season in Japan was analyzed in the view of meteorology. A case study of a 1997 July event suggested the pollution mechanisms that when Baiu front (synoptic-scale stationary front which causes rainy season in East Asia) is located just south (within ∼ 200 km) of urban areas and stays for several days, air pollutants emitted from the ground sources are accumulated in the calm and thin (several hundreds of meters) layer of cold air mass which lies north of Baiu front. This mechanism was confirmed by the Lidar observation data at Tsukuba and SPM concentration data at elevated monitoring stations on Tokyo tower. Another possible mechanism is the formation of a stagnant-layer in the central-northern part of Kanto Plain when Baiu front is located far north (e.g. on the Japan Sea). This pattern occurs when the south coast of the mainland Japan is dominated by the relatively strong westerly wind that flows along the periphery of the north edge of North Pacific anticyclone where pressure gradient is relatively steep. Under this condition, high mountainous area, west of the plain, obstructs the westerly wind to form stagnant (calm) layer downwind. This is a topography-dependent phenomenon and resembles those of the stagnant layer accompanying the “Boso local front” in the Kanto Plain which causes severe air pollution in early-winter.

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In order to investigate the characteristics of episodically yellow rain in Asian dust storm event, the size-resolved samples of raindrops were collected on a ground level in Kyoto. The soluble and insoluble fractions in size-resolved raindrops were analyzed by PIXE. Model calculations were performed to determine the elemental mass concentration as a function of raindrop size. It was found that the elemental concentrations in both soluble and insoluble fractions have a strong raindrop size dependence. S and Cl exhibit the predominantly higher mass loading in soluble fraction. Relatively good agreement was obtained between measured and calculated results for Si, S, and K. Furthermore, the chemical properties of the individual solid particles retained in raindrops were determined by the XRF microbeam system equipped at SPring-8, BL-37XU.

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We examined the annual budget and source-receptor relationships for sulfur in East Asia using a regional chemical transport model (HYPACT) coupled with the Regional Atmospheric Modeling System (RAMS). Model results are compared with the annual observation data, which are the daily concentrations of particulate SO₄^2- at Osaka and the annual SO₄^2- deposition measured by several organizations in Japanese Islands. HYPACT can reproduce the day-to-day variations of SO₄^2- concentration and the annual amount of SO₄^2- wet deposition. The annual spatial distributions of the concentration and deposition for SO₂ and SO₄^2- were estimated in 1995. The general features of distribution for SO₂ concentrations are similar to those for SO₄^2-. Both SO₂ and SO₄^2- concentrations are highest in the eastern part of China and is moderately high over the East China Sea and the western part of Japan. In contrast, the sulfur deposition distribution is completely different from the concentration distributions, because the wet deposition is strongly influenced by rainfall amount. Annual sulfur deposition in Japan is 49% from China, 21% from Japan, 13% from volcano and 12% from North and South Korea.

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Spatial distribution of mean particle diameter of cigarette main-stream cigarette smoke was measured immediately downstream of tobacco filters or tobacco column using an in-situ two-dimensional polarization-sensitive laser light scattering method. It was found that the mean particle diameter was about 0.2 μm and the spatial distribution was narrow. The mean particle diameter varied with the filter types and, therefore, the filters had different filtration efficiencies depending on the mean particle diameter. When main-stream smoke passed through a tobacco column of 5 mm to 40 mm in length from the char line, the number concentration decreased from 3 × 10¹⁰ to 1 × 10¹⁰ particles/cm³ and the mean particle diameter increased from 0.17 to 0.21 μm. Furthermore, we measured the filtration efficiency of a tobacco column using non-hygroscopic polystyrene latex particles with a low concentration, and found that the decrease in number concentration of main-stream smoke particles is similar to that measured for the test particles. Therefore, the major cause for the increase in main-stream smoke particles diameter with the length of tobacco column is not coagulation but condensation.

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Chemical compositions of atmospheric aerosols over the Northern and Southern East China Sea were measured using Aerodyne aerosol mass spectrometer. The results showed that the organic concentration was in the same level as the sulfate concentration at Fukue in Nagasaki, while the sulfate concentration was higher than the organics at Cape Hedo in Okinawa. The same tendency was observed by satellite observation. It is inferred that the organic substances influence the cloud formation much stronger in the northern part than in the southern part of East China Sea since the organics were extensively oxidized.

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Lung cancer is one of the most common causes of cancer death in Japan. Cigarette smoking is the major cause of lung cancer. Asbestos exposure is also known to cause lung cancer and malignant mesothelioma, which is a tumor derived from mesothelial cells lining on a serosal cavity. Pleural mesothelioma is the most frequent type of mesothelioma. The annual number of deaths from mesothelioma has been increasing rapidly, reflecting the past asbestos exposure in Japan. In this paper, we describe the mechanisms of carcinogenicity of cigarette smoke and asbestos, and review the etiology, clinical and pathological features of lung cancer and mesothelioma.

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