This paper comments on an overall problem from a viewpoint of epidemiology to promote a better understanding on ETS of the people other than medical scientists. It is included under the following items.
1. Chemical characterization of ETS.
2. Assessing exposure to ETS: Concentration of Nicotine in indoor air and concentration of surrogate in body fluids
3. Association between ETS exposure and lung cancer: Cohort study and case-control study. Meta-analysis.
4. Effects of ETS exposure on cardiovascular disease, pulmonary function, bronchitis, pregnancy and so on.
5. ETS and indoor air quality in commercial aircraft and other indoor environments.
6. Otehrs.

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The concentrations of polynuclear aromatic hydrocarbons (PAH) in the soil samples and the mutagenicity of benzene extracts from the soil samples on the roadsides in Kitakyushu City (11 samples), Kyushu Highway (21 samples) and Chugoku Highway Tunnel (13 samples) were investigated in 1986. The following results were obtained:
1. The average concentrations of tar in the soil samples in the three areas were almost the same from 24.2 to 29.8 mg/ g of soil.
2. The concentrations of the three PAH in the three areas were in the following order:
Benzo [ghi] perylene> Benzo [a] pyrene> Benzo [k] fluoranthene
The average PAH concentration in Kitakyushu City was, higher than those in the other two areas, and which were almost the same.
3. All tar material from the soil samples were mutagenis, and the mutagenicity with S-9mix was about twofold higher than that without S-9mix.
4. The contribution of Benzo [a] pyrene for the mutagenic activity of the soil samples was less than 2% and was very low at 0.06%, which is similar to that of airbone particulates, in Chugoku Highway tunnel.
5. The concentration ratio of Benzo [a] pyrene/Beuzo [ghi] perylene in the soil samples was 0.78 in Kitakyushu
City and about 0.4 in the other two areas. The causes of this ratio in Kitakyushu City is automobile exhaust and stack effluent from heavy chemical industry, but the soil samples in the other two are polluted mainly by auto mobile exhaust.

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A numerical model for environmental air flow was developed by using non-hydrostatic momentum and heat transport equations with boundary-fitted curvilinear coordinates system. which can be applied effectively to a small-scales region of complex-geometry such as urban area. For the development of the model, the methods of coordinates transformations and the schemes of discretization of advective term in heat transport equation were tested numerically for the gravity current of cold air flowing down over a steep slope of angle 45°
Performance of the boundary-fitted curvilinear coordinate transformation was compared with that of the conventional terrain-following coordinate transformation. The results showed that the boundary-fitted method can give a smoother and less-skewed grid system, and gives potentially less-erroneous flow and temperature fields, although no significant differences of computed flow and temperature between the two methods were found in the present case of the flow over the slope of angle 45°
The developed numerical model used fully-implicit time integration and the 3rd-order upwind difference for advective terms. By comparing with other numerical schemes such as the 1st-and 2nd-order upwind and central difference, the 3rd-order upwind scheme was evaluated in terms of numerical errors in the computed potential temperature and flow. For the stable numerical solution, the following conditions were necessary: the absolute values of the diagonal components in coefficient matrix of a set of linear algebraic equations, which resulted from the discretization of heat transport equation, are to be larger than the other components; and the local Peclet number is to be sufficiently small even in the case of the 3rd-order upwind. Reduction of grid size was an effective and important remedy for these conditions being satisfied. In the flow situation, in which use of large diffusivties was allowed, the reqnirement for small grig size was much relaxed.

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The histopathological changes in the respiratory organs of rats due to the combined exposure to tobacco smoke and O₃ were evaluated. Male Wistar rats were exposed to 0.5 ppm O₃ for 8 hours a day and 6 days a week and simultaneously to tobacco smoke 5 times a week for 2, 4, 8, 16, 20, 24 and 52 weeks, and killed for the histopathological study. The multi-layered epithelial hyperplasia were shown locally in the trachea, and the edema and collagen fiber hyperplasia were observed in the tracheal wall after the exposure for 4 weeks. The squamous metaplasia was noticed in the tracheal epithelium in 1 of the 7 rats, which were exposed for 24 weeks. The epithelial cell swelling and hyperplasia toward the alveoli were shown in the bronchioles by the exposure for 4 weeks or longer. The cells in the areas showing alveolar bronchiolization were composed of 2 to 3 layers, and were consisted of ciliated and non-ciliated epithelial cells. The squamous metaplasia was observed in some rats. These changes persisted until the exposure for 52 weeks. However, the number of the rats, which showed the fibrosis and the flattening of epithelial cells into a single layer, increased by the exposure for 20 weeks or longer, and no tumor generation was observed.

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An X-ray diffraction (XRD) method in combination with heavy liquid and magnetic separations was studied. After washing with carbon tetrachloride, a sample of 25-50 mg was centrifuged in a heavy liquid of the density of 3.0g/ cm³ in a specially designed tube with a narrow neck. The sediment including magnetite and hematite was transferred into a beaker, together with the heavy liquid of the lower part. Furthermore, the magnetizable matter included in the float was taken out by a magnet for complete separation of magnetite, and transferred into the same beaker to improve the recovery of magnetite. After adding silicon powder as an internal standard to the separated iron oxides, it was dispersed and filtered off by a membrane filter, then its XRD analysis was made. Magnetite or hematite of 0.1 to 0.9mg can be determined from the ratios of their integral intensity against the peak intensity of silicon. The XRD intensities from the reagent of magnetite or hematite and their pulverized ores, the effect of the composition of magnetite solid solution on the XRD intensity, and the influence of coexisting substances are also discussed. The lower limits of determination of both megnetite and hematite were estimated to be about 0.2%.

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