It is known that the gas-phase cigarette smoke and the gas-phase combustion smoke of polymers initiate lipid peroxidation and thus can cause oxidative biological damage via reaction of the apparently long-lived oxygencentered radicals in the smoke. In order to clarify the possible effects of the combustion smoke, any possibility that the gas-phase cigarette smoke, its model reaction gas, the mixture of olefin-NO-air, and the gas-phase combustion smoke of poly-methyl methacrylate (PMMA) may cause the oxidation of cysteine, which is an important thiol-containing amino acid, has been investigated using the Ellman method.
As the results, it is shown that all of the smokes can cause oxidation of cysteine, suggesting malignant biological effects. Although NO_x, which is contained in gas-phase cigarette smoke, can also cause the oxidation of cysteine, it is shown that the degree of oxidation caused with NO_x alone is smaller than that with the gas-phase cigarette smoke. And it is shown that the combustion smoke of PMMA not containing nitrogen compounds can cause the oxidation of cysteine.
These results suggest that oxygen-centered radicals should be involved in the oxidation of cysteine caused with the gas-phase cigarette smoke and the gas-phase combustion smoke of PMMA.

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Harmful effects of diesel exhaust particles on the lungs, especially tumorgenesis, had been reported in our previous experiments. In order to reconfirm the previous study and to determine the dose-response relationship of instilled diesel particles on rats' lungs, another instillation experiment was carried out.
Diesel exhaust particles were collected from a small sized engine (2400), and suspended particles were intratracheally instilled in the F344 (SPF), female rat's lung. 0.125 mg of diesel particles were instilled in group 1, 0.5 mg in group 2, 2 mg in group 3, and 8 mg in group 4...Group 5 was for control.
Animals were examined at 2 and 2.5 years after the instillation. No pathological changes were seen in the lungs of group 1 and 2. Mild inflammatory changes in the lung and a small number of lung tumors (3/47, 6%) were observed in group 3.
In group 4 large amount of diesel particles remained in the lungs accompanying with many foci of epithelial hyperplasia and focal fibrosis. Twenty-four among 56 rats (43%) had 40 lung tumors (12 adenomas and 28 carcinomasi). A statsitically significant number of lung tumors was found in group 4 compared with group 5 (2/ 48, 4%) and group 3 (3/47).
It is concluded that diesel particles are harmful to the lungs, and cause lung cancer in a dose-response relationship.

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Lateral eddy diffusion coefficient in the horizontal planes of scalar quantities K_y was investigated by smallscale diffusion experiments and turbulent measurements in the atmosphere. In order to obtain the lateral eddy diffusion coefficient K_y, a Lagrangian spectral function in the inertial subrange was determined based on the experimental results, then K_y was calculated by means of this function.
In stable conditions, the results indicated that the values of the lateral eddy diffusion coefficient, K_y normalized by the vertical eddy diffusion coefficient K_z in neutral conditions was found to be about 10, and the ratio was almost uniform with the stability ζ(≡z/L: L being the Monin-Obukhov length). On the other hand, K_z decreases rapidly with increasing stability in stable conditions due to the buoyancy effects. Therefore, K_y/K_z increases rapidly with increasing stability. When the ratio of K_y/K_z in stable conditions was normalized to that in neutral conditions, its stability dependence was similar to the results of laboratory experiments by Ueda et al.

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Effects of simulated acid rain on the growth of three-year-old fir seedlings (Abies firma Siebold et Zuccarini) were investigated. In this study, the simulated acid rain consisted of 1: 1 mixture of 1 M H₂SO₄ and 1 M HNO₃. The seedlings were treated with the simulated acid rain of pH 2.0, 3.0, 4.0, or deionized water (Control, pH 6.7) twice a week for 30 weeks (from May 8 through Dec. 4, 1991).
The red-brown visible foliar injury was observed in the seedlings treated with the rain of pH 2.0. At the middle sampling (July 31, 1991), the total fresh weight of seedlings treated with the rain of pH 2.0, 3.0, or 4.0 was significantly less than that of the control. The total dry weights of seedlings treated with the rains of pH 2.0 and 3.0 significantly reduced by 28% and 20% compared with the control, respectively. At the final sampling (Dec. 4, 1991), the total fresh and dry weights of seedlings treated with the rain of pH 2.0 significantly reduced by 23% and 29% compared with those of the control, respectively. The relative growth rate (RGR) and net assimilation rate (NAR) on plant dry weight basis during the growth period for 30 weeks were reduced corresponding to reduction of the rain pH. At the final sampling, transpiration rate in the dark, dark respiration rate and leaf sulfur content of seedlings treated with the rain of pH 2.0 significantly increased.
These results suggested that the fir seedlings is sensitive to acid rain of pH 3.0 and above.

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Two sampling points were set up on the both sides of expressway to investigate the influence of road traffic (expressway) on the chemical composition of rainwater. Statistical test was applied to the analytical data of two sets of samples for rainfall events with southern wind direction. It is proved that in the warmer period (May-Oct.), rainwater samples collected at the leeward point near the expressway are considerably higher in nitrate, sulfate and ammonium concentrations than those collected at windward point 3 km apart from the expressway. Inspite of the increase of nitrate and sulfate ions in the rainwater, collected near the expressway, its acidity is not so high as we expected. It is a result of neutralization of acid substances in the rainwater by ammonia exhausted from three-way catalyst cars. It is also demonstrated that at the point of near the expressway, especially in the warmer period, ammonium and nitrate concentrations in the rainwater are mutually well correlated, and furthermore, their molar ratio is close to 1: 1. This fact suggests that ammoniumion exists mainly as nitrate salt in the air of the environs of expressway.

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In this paper, the authors have described on the administrative activities for the CFCs problems, the consumptions of CFCs in Thailand and the operations with CFCs at some factories located around Bangkok. Thailand depends upon the imported CFCs. The CFC-11, CFC-12, CFC-113 and Halon-1211 consumptions in Thailand are 3, 090 ton, 4, 140 ton, 3, 270 ton and 108 ton respectively in 1991.
Main uses of CFCs in Thailand are for solvents (40%), refrigeration (20%), air-conditioning (17%) and plastic foam products (15%).
The main countermeasures in factories using CFCs are the adoption of the alternative substances such as water and methylene chloride for plastic foam products and trichloroethylene for cleaning, the recovery of CFCs and the improvement of using processes.

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