Unfavorable occurrence of a variety of communicable diseases in experimentol animals hawe long been serious problem in every laberatory. It has been also true in the field of air pollution research, in which respiratory infection has been inevitably a major interest, under the situation that the most of all test materials should usually be administered through respiratory route.
Possible difficulties arising from a contamination and/or provocation of respiratory infections, were presented and discussed. Special emphasis was made to mild or latent respiratory infections, which might easily lead to misunderstanding or even false-positive results in interpreting the obtained date from pathological, biochemical as well as respiratory-physiological examinations.
Shift of longevity and incidence of pneumonia from several experimantal series in our laboratory during 1963 to 1973 were presented and interpreted from a view point of changing quality and way of sanitation of the animals. In using conventional animals and conventional control without any air-conditioning, fifty percents survival was only 7.8 months at around 1963 with 100% occurrence of pulmonary absess, which was main cause of spontaneous death of the animals. After a new animal house with complete airconditioning was established in 1966, fifty percents survivals were raised to 23.5-26.3 months and incidence of palmonary infections were lowered to 5-20 percents, the most of which were terminal events. Under more careful sanitary conditions including desinfections of food and water and other equipments, recent results from an inhalation experiment in using a SPF rat, showed 28 months in fifty percents survivals in control exposure group with practically clean lungs.
It should be always born in mind that the quality of the experimental animals and microbiological environment of the animal facilities should be adequately matched in the sence of ecological situations. More stable and practical measure in microbiological control are urgently required for further fruitful development of experimental study in environmental research.

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The role of nitrogen dioxide (NO₂) in the developing pulmonary tumors was investigated in strain A mice given repeated injection of 4-nitroquinoline 1-oxide (4NQO) in this study.
Experimental mice (1-month-old) were divided into 4 groups. 0.25 mg of 4NQO dissolved in 0.1ml of an admixture of olive oil and cholesterol (100: 5) was injected subcutaneously into the backs of mice 5 times at weekly intervals. Mice were exposed to an average 10 ppm of NO₂ 2 hours each day, five days a week for 50 weeks.
6 of 13 mice bore lung tumors in the group I receiving 4NQO and NO₂, 9 of 13 mice in the 4NQO only group II, 3 of 26 mice in the NO₂ only group III and 4 of 50 mice in the no-4NQO-no-NO₂ group IV served as controls. Lung tumors appeared as multiple, small white nodules in the group I and II but as only one in the group III and IV grossly. In the microscope, tumor cells were disposed in either a compact or an adenoid pattern supported by delicate fibrous stroma and thin-walled blood vessels, but tumor cells in the group I and II show higher grade in cellular atypia than those in the group III and IV.
It is confirmed that the effect of combined treatment with 4NQO and NO₂ is not greater than would be expected on the basis of sequential tumorigenic effects of synergism or summation, because the difference in lung tumor incidence between the group I and II is not highly significant. On the other hand, the exposur to NO₂ caused some epithelial cells of terminal bronchiole to proliferate and led to enlargement of the alveoli and hyperplasia of lymphoid tissues in periarterial tissues.
The results of this study thus suggested that the exposure to NO₂ do not induce neoplastic changes in mice lung and may tend to reduce tumorigenic activity of 4NQO.

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The respiratory tract keep the biological balance of microbial flora and its physiological defense mechanisms. This balance changes cause to reduction of infectious protective mechanism and consequently to acceration of microbial infection. From this of the above, micro organisms, especially the change of microbial flora should be duly considered in experimental approaches on the health effects of air pollution.

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Nitrosyl-hemoglobin (NOHb) was detected by electron spin resonance spectrometry from the blood of mice and rats exposed to 7 ppm nitric oxide, but in rabbits it was detected only when the blood was added with sodium dithionite. To elucidate this species difference some comparative experiments were done using the blood of mouse and rabbit. Rabbit blood showed higher affinity to oxygen, and smaller production of NOHb after addition of nitrite than mouse blood. These results might explain the reason why NOHb was not detectable in rabbit blood during the exposure of nitric oxide.

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Benzo (a) pyrene (Bp) hydroxylase activity in liver tissue of 6 stocks of mice were assayed by the method of Wattenberg et al. with slight modification. The Bp activity which was expressed as the units of supernatant in 15 minutes of incubation were 477±15 in male (m) and 485±27 in female (f) of C57BL/6Ha, 212±8 (m) and 234±21 (f) in C3H/StHa, 165±7 (m) and 284±4 (f) in DBA/2, 286±13 (m) and 314±24 (f) in Ha/ICR Swiss, 267±11 (m) and 265±15 (f) in A/St, and 198±12 (m) in C3B6F₁ respectively. The C57BL/ 6Ha mice had the highest activity, two to three times as high as that in the DBA/2 mice, which had the lowest enzyme activity. The very pronounced induction of Bp hydroxylase activity by i. p. injection of Bp was observed in the C57BL/6Ha and C3H/StHa strains and their F1 hybrid. Further study is in progress to determine whether there is a relationship between enzyme activity to and sensitivity polynuclear aromatic hydrocarbon carcinogens.

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Oxidant damage to morning glory (Scarlet Ohara) was studied in non-filtered air greenhouse and the correlation between the leaf damage index and the oxidant dose was obtained to make clear its validity as an indicator plant.
1) The damage was obserbed on the leaf surface of the morning glory upon its exposure to oxidant in a non-filtered air greenhouse, but not in a filtered air greenhouse. Two forms of damage, chlorosis and necrosis, were seen and the latter was induced by higher dosage of oxidant.
2) There was a strong relationship between the leaf damage index and the oxidant dose. Oxidant caused leaf damage at dosage more than 49 pphm-hr sumed up the oxidant concentration above 8 pphmhr, 44 pphm-hr above 9 pphm-hr and 43 pphm-hr above 10 pphm-hr in the last ten days of August, and 72 pphm-hr above 8 pphm-hr, 75 pphm-hr above 9 pphm-hr and 52 pphm-hr above 10 pphm-hr in mid- September.
3) The relationship between the oxidant dose and the total leaf damage area of five leaves located below the uppermost damaged leaf was similar to that of leaf damage index of all leaves investigated. Thus, one can simply the investigation of leaf damage by taking the data of upper five damaged leaves.
4) In the summer, the growth rate of morning glory was very rapid and one or two leaves developed per day. As the leaves sensitive to oxidant were formed every day, it was possible to make observation of leaf damage even under the frequent occurrence of photochemical smog in ambient air.
The morning glory is an effective indicator for oxidant, because of its ease in investigation and the high correlation between the oxidant damage and the oxidant dose in the ambient air.

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It was shown in the previous report that the oxidant damage on morning glory was observed at the specific leaf order.
The experiments were carried out in order to clarify the relationship between the leaf order and the stomatal opening, leaf expansion, the contents of chlorophyll and soluble carbohydrate. The effect of the leaf age on the order of damaged leaf was also verified.
One leaf developed per day in mid-September and the uppermost leaf damaged by oxidant was about the fifteenth leaf from the top. The leaf already ceased its expansion was susceptible to oxidant. The correlation between the stomatal opening and the sensitive leaves was seen on the upper leaf surface rather than on the lower leaf surface. The content of chlorophyll a, b and reducing sugar in the leaves reached its maximum value at the ninth leaf and maintained low value at the damaged order.
Thus, one can safely assume that the leaves sensitive to oxidant are located below the leaf having high metabolic activity.

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Epidemiological studies on the subjective symptoms of students affected with photochemical air pollution were made in the periods of Sep. 13, 21, 22, 1972 (School A), and on Oct. 3 (School B) in Osaka.
A statistical analysis following Hayashi's Quantification Theory (Pattern Classification) revealed that the symptoms were to be classified in to three types: Type A with a chief complaint of eye irritation, Type B complaining of cough and sore throat, and Type C with nausea, dizziness, and numbness of the extremities.
Those three types were either interchangeable or overlapping depending upon the time and day of examination.
Difference in type classification seems to show different quality of photochemical air pollution.

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In order to elucidate the area dependency and the correlation of the concentrations of various trace metallic elements in the atmosphere over west-Kobe (Nagata) and east-Kobe (Higashinada) districts, the airborne particulates whose diameters are smaller than 10μm were collected on a millipore filter (AAWP- 105), using a low-volume air sampler (FKS-Type) for 15 days continuously, and the analysis of 14 elements were made by the use of emission spectrophotometric method. The samplings of the airborne particulates were made in the period from December in 1972 to January in 1974.
As the analytical results, in the mean values of the elemental composition in a year, and in the seasonal variation patterns on the most elements, similar relationships were obtained in the both districts. And, the components could be classified to soil origin and artificial one. As a general tendency, the contents of the Nagata district were about 20% higher than that of the Higashinada district.

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