fhe present status of suspended particulate matter (SPM) pollution and countermeasures against it in Japan are summarized by discussing examples mainly in Osaka and Kawasaki.
The SPM air quality standard was not met at 43.3% of general monitoring stations, most of which are located in urban areas, in 1986. The emission control for stationary sources have been found to effective in Osaka and Kawasaki. However, the contributions of diesel emission and secondary particulate formation are still large. Therefore, it is necessary to take comprehensive countermeasures to control it completely.
Research results on SPM behavior in the atmosphere, diffusion model to deal with long life time particulates and qualitative secondary formation mechanism are inevitable to the future SPM control planning.

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In order to clarify the influences of dust scraped off from road by studded tires of automobiles on human health, the investigation was carried out on mutagenicity to S. typhimurium TA98 and on concentrations of polynuclear aromatic hydrocarbons (PAHs) in airborne particulates collected at road-sides in Sendai city from November 1983 through December 1985.
Amount of airborne particulates rose with increase of the numbers of automobiles equipped with studded tires. The particulates collected during winter season coresponded for the amount of 4-5 times of those in summer. The mutagenic activities and PAHs contents per m³ of air showed logarithmic normal distribution. Those per mg of tar showed normal distribution. Good correlations were obtained between PAHs contents and mutagenic activities (±S9 mix) per mg of tar (P<0.01). Mutagenic activities and B (a) P contents per m³ of air in winter season were higher than those in summer (P<0.01). Whereas, mutagenic activities per mg of tar in summer were higher than those in winter (P<0.01). And no difference could be observed in B (a) P contents per mg of tar between in summer and winter season. Asphalt has suppressing effects on the mutagenic activities of B (a) P and B (ghi) P. These inhibitory effects of asphalt on the mutagenicity of PAHs were suggested to be one of the reasons of tar being less mutagenic in winter than in summer.

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To study airflow and transport dispersion over complex terrains, field and wind tunnel experiments have been conducted for Mt. Tsukuba. The field observations were done under nocturnal inversion condition. Vertical profiles of wind velocity and direction by pilot balloons at five points, vertical profiles of air temperature by radiosondes have been done.
The field observations show that together with nocturnal inversion, a stagnant zone upstream of a ridge and high wind on the lee slope develop.
The wind tunnel simulation has been done in the Thermally Straified Wind Tunnel of National Research Institute for Pollution and Resources. The scale of the topographic model was 1/7500 for horizontal and 1/5000 for vertical. The nocturnal inversion was produced by heating airflow to 40°C and chilling the floor of the test section at 10°C. The wind speed was set at 0.4 m/s from the Froude number similarity. The results show that the transport dispersion under noctural inversion shows drastic changehdue to the relative height of source to the dividing streamline (DS). The vertical diffusion bellow the DS is restricted by the height, ie., pollutant does not go over the peak.
On the contrally, the lateral diffusion becomes relatively large.
For pollutants released above DS, the diffusion does not show essential differnces from that of adiabatic condition.

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Effects of ozone exposure on the Sidman-type conditioned avoidance response in rats established with ten sessions of training were examined. Although a slight, but not significant, increase in number of the lever-pressing was shown at 60 min of ter the start of exposure to 0.5 or 1.0 ppm of ozone, a marked decrease in the lever-pressing and a concomitant increase in the number of shocks in rats at 90 min after the start of exposure to 1.0 ppm ozone. Such suppressions in the avoidance response in rats were shown at 45 min during the exposure to 2.0 ppm ozone. The avoidance responses in the rats exposed to 1.0 or 2.0 ppm of ozone could recover at 60 or 120 min, respectively, after the forced ventilation with air. These results suggest. that ozone impairs an operent behavior to avoid a suffering situation from electric shocks at concentrations of 1.0 ppm and more.

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