Main air pollutants in Japaneseurban area are NO₂ and diesel exhaust particles (DEP), because diesel engine powered cars has been increasing steadily. People are anxious about that the air pollutants may cause asthma. There are clinical and epidemiological studies to suggest that diesel exhausts may cause asthma. However, it is not yet confirmed by experimental study. Here, I introduce our recent experimental data that DEP produces superoxide (O₂^-) and hydroxyl radical (·OH) during in vitro autooxidation reaction and in vivo xenobiotic metabolizing reaction of quinone like compounds in DEP, and these active oxygens cause lung injury and superoxide dismutase conjugated with polyethylene glycol (PEG-SOD) inhibit the injury. Further-more, we found that essential features of asthma such as chronic inflammation with eosinophil-infiltration, mucus hypersecretion and airway hyperresponsiveness has been caused by repeated intratracheal instillation of DEP, and that the active oxygens generated from DEP may play an important role to cause asthma like symptoms, because PEG-SOD pretreatment have depressed the three essential features of asthma like symptoms.

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Snowfall and snowcover in various layers were sampled so as to analyze the main chemical constituents at the two sites of different elevation on the southeastern slope of Mt. Myoko in southwestern area in Niigata Prefecture. It was shown from the distribution of chemical constituents in various layers of snowcover that chemical constituents moved from the upper layer to the lower layer, and that their concentrations decreased in the following order: newly fallen snow, settled snow and granular snow. Each concentration of components in the new snow layer was lower than that of snowfall collected drung the same period at both sites, so that the chemical constituents were considered to elute from the snowcover. The rates of elution were different among the components. Nitrate, SO₄^2-, NH₄⁺ and Ca²⁺ were more easily eluted than Na⁺, Mg²⁺ and Cl^-, which are supposed to be originated from sea-salt. Observing the decreased amount of constituents in the same layer in the snowcover after a certain interval, the chemical components were supposed to have moved from upper to lower layer in the snowcover, and a part of them eluted from the layer.

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Comparatively long-term exposure of guinea pigs to a mixture of ozone (O₃) and nitrogen dioxide (NO₂) has been shown to cause airway hyperresponsiveness (AHR) to infused methacholine (Mch); however, the mechanism by which this occurs is not known. In this study we examined the roles of leukotrienes (LTs) and thromboxane B₂ (TXB₂) on the AHR induced by this combination of gases. Guinea pigs were continuously exposed to either filtered air or to a combination of 2 ppm NO₂ and 0.2 ppm O₃ for 8 weeks, then divided into two groups. The first group was anesthetized and intubated, then pulmonary mechanics and airway responsiveness to infused Mch were measured. The second group underwent bronchoalveolar lavage (BAL), and levels of LTs and TXB₂ were measured.
We found that exposure to O₃ and NO₂ did not alter static respiratory compliance, or baseline measures of respiratory flow resistance (R) or dynamic compliance (Cdyn). Exposure to the combined gases decreased ED₂₀₀R (the dose of Mch necessary to cause a 2-fold increase in R over baseline) significantly from 3.24±0.16μg/kg/min, which were seen in the filtered air-exposed animals, to 2.29±0.29μg/kg/min (p<0.05). The ED₅₀Cdyn (the dose of Mch necessary to reduce Cdyn to 50% of its baseline value) of this group was also significantly reduced from 3.67±0.46 to 2.39±0.19μg/kg/min (p<0.05). The level of LTB₄ recovered in the BAL fluid increased significantly from 94.7±8.7 pg/ml, in the air-exposed controls, to 139.5±8.8 pg/ml (p<0.005). Though not statistically significant, exposure to O₃ and NO₂ also resulted in an approximately 2-fold increase in TXB₂, from 87.2±33.0 pg/ml in the air-exposed animals, to 161.8±47.9 pg/ml in the O₃ and NO₂. In all of the animals, the levels of LTC₄, LTD₄ and LTE₄ were below detectable limits (<60 pg/ ml for LTC₄;<80 pg/ml for LTD₄ and LTE₄).
After 4 weeks recovery period, airway responsiveness, as well as BAL levels of LTB₄ and TXB₂ returned to normal. These data support the hypothesis that LTB₄ and TXB₂ play a role in the AHR induced by 8 weeks exposure to O₃ and NO₂.

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Acid fog and pollution have been observed on Mt. Akagi almost every fall since 1984. In this study, we considered the transportation process of air pollutants from the Kanto plain to Mt. Akagi, based on the fog and air pollution data obtained from field experiments conducted in September 20-28 in 1990. It was found that fog developed on Mt. Akagi shows very high NO₃^-/SO₄^2- ratio compared with those of ordinary deposition in Japan. The behaviour of air pollution on Mt. Akagi can not be explained only by the air pollution and wind condition near the ground surface in the Kanto plain. Therefore, a 3-dimensional wind field was estimated by the variational procedure, and the transportation process of particles released from central area of Tokyo Metropolitan was visualized.
Typical transport pattern of air pollutants from the Kanto plain to mountaneous area became clear. The transportation process of high concentration of ozone observed on Mt. Akagi in the evening became definite. Especially, it could be explained that the high ozone concentration in the evening of September 24th occured by the accumulation of air pollutants by the stagnation of air mass over the Kanto plain.

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Cucumber plants (Cucumis sativus L.: cv. Shimoshirazu-jibaikyuuri) were exposed to 0.10, 0.15 or 0.20μl·L^-1 O₃ and UV radiation (190 mW·m^-2UV-B_BE), alone and in combination, for 6 hrs. a day (9: 00-15: 00), 6 times during an exposure period of 15 days from the 7th to the 21st day after sowing. The dry weight growth of the plants was reduced by the exposure to 0.15 and 0.20μl·L^-1 O₃ or UV radiation, but was not affected by the exposure to 0.10μl·L^-1 O₃ alone. There were significant interactive effects of 0.15 or 0.20μl·L^-1 O₃ and UV radiation on the dry weight growth of root, stem and whole-plant, and the degree of growth reduction in the plants simultaneously exposed to O₃ and UV radiation was greater than that in the plants exposed to O₃ or UV radiation alone.

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Hourly and annual oxidant (O_x) concentrations measured at monitoring stations in the Kanto and Kansai areas from 1978 through 1990 were statistically analyzed to examine annual trends in photochemical air pollutant behavior. The spatial and temporal annual trends of the daily maximum O_x concentration, and of the NMHC and NO_x cencentrations and the NMHC/NO_x ratio were analyzed. The analysis shows, in relation to the daily maximum O_x concentrations during the period 1978-1990, that:(1) the time of the daily maximum O_x concentration occurs later in a day, and (2) the location of the daily maximum O_x concentration shifts inland away from the major emission areas (Tokyo in the Kanto area and Osaka in the Kansai area). In relation to the NMHC/NO_x ratio the analysis shows that the ratio has decreased over the 13-years period. This decrease may be one explanation for the above-described changes in the daily maximum O_x pattern. Numerical simulation may clarify the link between the daily maximum O_x concentration trends and the NMHC/NO_x ratio.

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