From 1975, in cold regions where there is a tendency for snow to accumulate, it became clear that road particulates, which occured as a result of the use of studded tires, brought about a new environmental problem. In particular, the notable vorsening of pollution in urban areas in Hokkaido, Miyagi, Nagano, etc. called for a resolution to the urban pollution. Although it is a slightly old story, the difficulties and details encountered by Miyagi Prefecture up until the establishment of the Law on the Prevention of the Generation of Particulates from Studded Tires and outline the movement of the SPM Measures are introduced.

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In order to clarify the relationship between nutrient status of ascorbic acid and the effect of ozone, rats unable to synthesize ascorbic acid, ODS-rats, were supplemented with ascorbic acid in drinking water at concentrations 0 to 10 g/L for 3 weeks, followed by exposure to 1 ppm ozone for 4 hours and their effects were studied.
1. The protective effect of ascorbic acid against ozone toxicity was demonstrated by the observation that an increase of protein concentration in bronchoalveolar lavage fluids (BALF) by ozone exposure was inversely proportional to the dose of ascorbic acid supplementation. On the othter hand, the decreased number of macrophages in BALF by ozone exposure was unaffected by the supplementation of ascorbic acid. These differences were assumed to be related to the protective action of ascorbic acid in the alveolar lining layer.
2. By ozone exposure, the ascorbic acid level in the lungs was decreased in proportion to the supplementation of ascorbic acid. It was more decreased in BALF than in tissue, and the oxidized form of ascorbic acid was increased in BALF. It is suggested that the reduction of ozone by ascorbic acid might occur in the alveolar lining layer.
3. The ascorbic acid level was increased in liver and was decreased in adrenal by ozone exposure. These observations show that the effect of ozone on ascorbic acid is not restricted to the lungs.

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To estimate the air purification ability of foliage plants in indoor environments, the stomatal conductance of 10 foliage plants was measured using a diffusion porometer and their absorption of atmospheric formaldehyde was compared. The stomatal conductance of the studied plants ranged from 0.01 (Guiana chestnut) to 0.10 molm^-2s^-1 (Nephthytis) near a sunny window in the daytime and Nephthytis, Clevelandii, and Benjamin tree had higher abilities to absorb atmospheric formaldehyde. Individual variations in the stomatal conductance of Nephthytis, Clevelandii, and Benjamin tree were relatively low. Hourly variation patterns of stomatal conductance for these three foliage plants were similar to those of photosynthetic photon flux density in the daytime. The formaldehyde concentration in a conference room, which contained some smokers and a potted Clevelandii plant (total leaf area; 0.9m²), was estimated by the mass balance model. The mean indoor formaldehyde concentration in the presence of the potted Clevelandii was estimated to be 5% lower than that without the plant. It is concluded that foliage plants contribute to air purification in indoor environments.

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Correlations between response values of an odor sensor and the concentration of malodorous substances were invenstigated using the semi-conductor type odor sensor (XP-s2gS: for sulfur compounds). Odors were continuously measured in a stainless-steel chamber or outside near the emission source for a week. Characteristics of the odor sensor were also studies.
The results show that the response values of the odor sensor can be predicted from the odorants concentrations in the field if sensitivity check and zero-level adjustment of the odor sensor are periodically performed, and that the concentrations of malodorous substances can also be predicted from the response values of the odor sensor when the ratios of the concentrations of malodorous substances are roughly constant. During the measurement of odor in the chamber, the odor sensor was also found to be useful for detecting byproducts that were generated from a deodorant filter of an air cleaner.
After the odor sensor was used for several months, it was found that the linear regression line between response values of the odor sensor and odor concentrations shifted parallely because of insufficient zero-level adjustment, and that the sensitivity of the odor sensor in a high concentration range decreased because of the adsorption of substances by the odor sensor of the instrument.

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A test vehicle was installed with a full-flow burner regeneration type diesel particulate filter (DPF) using a SiC honeycomb to examine the application of DPF to heavy duty diesel truks, and a field test was performed. The test vehicle ran 35, 348 km for the period, and a regeneration frequency of DPF reached 903 times. Exhaust smoke was not observed during this period. In addition, the filtering efficiency of particulate matter (PM) was confirmed to continue at about 90% as a result of the regular measurement of PM. It was determined that there was no deterioration in the trap performance of the SiC filter from these results. Moreover, nothing essentially wrong with the DPF occurred during the period, and no influence on driving peformance was shown. Therefore, it is thought that the durability and reliability of DPF are fundamentally sufficient. On the other hand, an increase in the fuel consumption due to fuel regeneration became 8.4% in the suburban road course, 4.7% in the highway course, and 8.6% in the Tokyo road course. When DFP was applied to the heavy duty diesel truck, it was clarified that the fuel consumption improvement was necessary.

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A diesel particulate filter (DPF) using a SiC honeycomb with a high heat resistance was installed in a heavy duty diesel truck. During the field test of approximately 35, 000 km, exhaust gas was measured in the chassis dynamometer. The influence of the DPF installation on exhasut gas was investigated. The results were as follows.
(1) With this DPF using SiC, pressure loss by the installation was small. Therefore, a big effect was not shown on exhaust gas or fuel consumption.
(2) “White Smoke” was visually observed at regeneration. This phenomenon was confirmed as an increase of exhaust gas.
(3) The total emission mass including the increase in this exhaust gas was calculated. Then, the total emission mass increased 1.19-1.31 times for THC and 1.53-1.79 times for CO, respectively, compared to no DPF. There was no influence on the NO_x. On the other hand, the filtering efficiency of particulate matter (PM) was 83-88% by regeneration. The filtering efficiency decreased slightly compared to no regeneration. By a CO₂ conversion method, filtering efficiency of the carbon component (as Soot) and the volatile component (as SOF) of PM was examined. The cause of the above-mentioned white smoke was examined. The results were as follows.
(4) The filtering efficiency of Soot was nearly 100%. However, that SOF was about 60%.
(5) It was confirmed that the majority of the white smoke originated in SOF. Therefore, to decrease these components improved filtering efficiency by adding an oxidation catalyst to DPF should be studied.

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The properties of a semiconductor ammonia odor sensor were investigated in the laboratory and field. The laboratory results showed that the ammonia sensor was sensitive to water vapor pressure as well as ammonia concentration. In the field, ammonia concentration was calculated from the ammonia odor sensor values and the water vapor pressure. The calibrated ammonia concentration had a good relationship (R=0.80, n=57) with ammonia concentration by an acid-trap calorimetry method, where the ranges of ammonia concentration and water vapor pressure were -100 ppbv and 4-6 hpa, respectively. The ammonia odor sensor can measure concentrations of ammonia as 10 ppbv, which is the background level in agricultural fields, with an estimated error of ±9.72 ppbv.

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Concentrations of aerosol components and NO₂ in the neighborhood of Visayas Avenue were measured by a conventional high volume air sampler and passive sampler, collected during 2nd December through 7th, 1997, in Quezon City, Philippines. TSP levels at that site ranged from 150 to 256μg/m³ which were sometimes over the National Environmental Air Quality Standard (230μg/m³). Average concentration of lead was 0.43μg/m³. The concentration of lead decreased markedly compared to those of 1980-1990 due to the introduction of unleaded gasoline. But this level is in the lower vicinity of the WHO's for lead longterm guide line (0.5-1.0μg/m³). The behavior of Total Suspended Particulates (TSP) shows good correlation with lead and NO₂ concentration, threrfore the contribution of mobile sources is presumed. Concentration of iron was the highest concentration among measued components in the aerosol. Average concentrations of water-soluble ions (SO₄^2-, NO₃^- and Cl^-) were 5.10, 1.77 and 3.93μg/m³, respectively. Sulfate was the dominant chemical component followed by chloride. In spite of the long distane (12 km) between measuring the site and sea shore, the concentration of chloride was higher than Yokkaichi (Environmental Science institute, which is 3 km from the shore and located about 50 m from National Road 1.) Therefore anthropogenic sources rather than sea-salt-particles were assumed to be the cause. In contrast to the concentration of chloride, the average concentration of nitrate was 1.77μg/m³, which was one-third of the value of Yokkaichi in 1992. Due to energy sources largely dependent on crude oil in the Philippines, the concentration of vanadium was higher than Yokkaichi in 1992, and correlation coefficients with NO₃^- and SO₄^2- were high.

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