Carcinogenic polycyclic aromatic hydrocarbons are widely distributed in our environments as pyrolytic products of organic matters. Analytical works of these hydrocarbons previously published were reviewed and their significance for human carcinogenesis was discussed. There is no absolute proof yet that these carcinogenic hydrocarbons are carcinogenic to man. In view of the dose-response relationship of the carcinogens and of the factors affecting it, however, it seems reasonable to consider that materials containing these hydrocarbons, even minute in amount, can be potent carcinogens for man. Thus, ordinary wisdom indicates the desirability of minimizing or eliminating all sources of carcinogenic polycylic hycrocarbons from out environment.

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From the environmental and medical records obtained by factory surveys in five staple fiber and artificial silk plants, average CS₂ concentration in the spinning room, expired CS₂ concentration of the workers during and after the day shifts, urine CS₂ level in the following morning before entering the work, and clinical signs including subjective complaint and results of laboratory tests were summarized to evaluate the occupational exposure to CS₂ with a view to industrial hygiene control.1, CS₂ level of the expired air was gradually elevated during the shift and reached equillibrium to the environmental CS₂ in about 3 hours. At the excreting stadium the expired CS₂ level fell sharply in the first 20 minutes and continued tracing an exponential or parabolic curve. The form and the level of this curve was varied by the individual difference in accordance with the serum cholesterol level. An animal experiment revealed in this connection, that the coefficient o〓foo istribution of environmental vs. blood CS₂ concentrations rose when the serum cholesterol level was elevated after four month exposure to CS₂. 2. Threshold limit of the average CS₂ concentration in the working place was estimated to be 15 ppm on 8 hour basis, when the free CS₂ concentration in the morning urine before entering the shift showed a threshold level and expired CS₂ concentration immediate after the shift was about 2 μg/dl. When values exceeds this level, various clinical signs and complaints as shown in Figure 4 began to be observed in several workers. As the indices of industrial exposure to CS₂ values obtained by analyses of expired CS₂ at the end of the shift and urine at the beginning of the following shift are extremely useful for evaluating the industrial hygiene practice and control in the viscose rayon industry.

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Pulmonary airflow resistances were calculated by measuring the alveolar pressure and the flow rate in and out the airway by interruption technique and pneumotachometry in 13 healthy male adults, and responses were compared after five minute inhalations of submicronic NaCl aerosols, SO₂ of the concentration of 1.6∼56.0 ppm, and SO₂-aerosol mixture. Monodisperse saline aerosols with CMD 0.22μ were generated from 2% sodium chloride solution through Dautrebande D₃₀ device, and SO₂ inhaled was ejected from the iron pressure tube through capillary rotameter to obtain constant concentration. While the inhalation of sodium chloride aerosols showed no irritating response in all the cases, SO₂ gas induced remarkable increase of the airway resistance; this enhanced response was 2∼50% above the pre-experimental control value. When SO₂-aerosol mixture was inhaled, the percentage response change increased synergistically, showing 20∼80% above the control valne. A hypothetic explanation on the synergism may be made by La Belle's theory which involves pulmonary penetration of particles and gas in terms of the size and the Henry's constant.

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Experimental studies were made on the curve of equal sensitivity of the human ear for vibration. In cases of vertical vibration obvious difference was observed as regards points representing equal sensitivity at low frequencies and at high frequencies. The curves were similar in cases of longitudinal vibration and of transversal vibration.

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Experimental studies were made, with the following results on the discrimination capacity of vibration frequencies in the case of vibration of the whole body. 1) The frequency difference △f (c.p.s.) the discriminated in the case of increasing was found to be smaller in the range of frequencies from 1 to 6 cycles per second and persisted down to the range from 0.79 to 0.05 c.p.s., △f of 10 cycles per second showed a sudden change of increase 10c.p.s, its value were from 1.82 to 2.80c.p.s. 2) In the case of decreasing frequencies, △f of the amount from 1 to 6 cycle per second was found to be smaller as well as the case of increasing frequencies. Above 10c.p.s., △f were from 1.17 to 2.61c.p.s.. 3) △f in the case of increasing frequencies was found to be greater than in that of decreasing. 4) △f/f at 1c.p.s. was found to be the maximum and the higher the frequency of vibration, the less △f/f. But, △f/f in the case of 10c.p.s. was larger than in the case of frequencies from 5 to 30c.p.s.. 5) In spite of the differnce of geometric components as well as of the amplitude, △f/f remained constant.

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