As the determination of the maximum allowable concentration of organic solvents requires investigations of the physical responses of man to specified gas concentrations, a gas chamber for that purpose was constructed. The chamber is 2.23 m wide, 3.55 m long, and 2.80 m high, the cubic space being about 23 m³, and it is large enough for two or three men to work to a certain extent at a time. All the walls are shielded with wire netting for undisturbed electrophysiological experiments. The inside of the chamber is furnished like an ordinary living room lest the subject should be strained unnecessarily. Gas generators, concentration measuring apparatus, and electro-physiological apparatus are all equipped outside so that the experimenter may easily operate them observing the inside through the window. To produce a constant gas concentration a method is adopted in which a constant fresh air flow is kept through the air duct in which the solvent vapour is being shot with a spray gun; the quantity of the vapour is adjustable with a screw. An experiment on the function of the chamber under conditions, that tow men were working moderately within and 3.5 m³/min acetone gas was kept sending in, obtained a satisfactory result in which no liability of CO₂ accumulation was noticed and the concentration of the solvent kept its stability throughout 6 hours' operation after the first 40 minutes of variation. The range of the concentration to be adjusted with comparative ease was 100∼2000 p.p.m. Though the result of the experiment was pretty satisfactory, the points required for further improvement are: 1) that the noises caused by a fan and by the spray- gun be abated, 2) that a climate adjuster be installed, 3) that the adjustment for concentrations lower than 100 p.p.m.or higher than 2000 p.p.m. be further contrived, 4) that an anemometer for gauging the quantity of the air flow be equipped, and 5) that a gas-chromatograph for the measurement of solvent concetrations be equipped.

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One of the important points in investigating the physical responses of animals to organic solvents, in view of their maximum allowble concentrations, is to expose the animals to various concentrations of solvent gases for a long time. In this case, the longer the exposure, the more desirable are some pertinent devices to spare the operator unnecessary burdens in the control and operation of the exposure apparatus and in the care of the animals. Thus, eight samples of experimental gas chambers for longterm exposure were made. In these chambers the following points were devised. 1) A time swich was equipped to start and to stop daily exposures automatically. 2) A vaporizer and a flow stabilizer especially for the high-concentration solvent gas were newly deviced to keep constant the concentration in the chamber. 3) The principle of the present device is to obtain the aimed gas concentration in the chamber by leading into the chamber the solvent gas diluted with fresh air. To control the concentration with ease, a deliberate care for flow of the solvent gas and of fresh air is required. For that purpose a float meter (or an orifice tube) was used in the case of the former, and a dynamic pressure-type flow meter in the latter. 4) Contrivances made of the structure of the chamber are as follows. i) In order to made easier the care of animals breeding, it is desirable that the animals are kept in the chamber without a break and exposed to the solvent gas daily for certain hours. For that purpose special regards were paid to the capacity and structure of the chamber ready for observation of animals and for cleaning. ii) To get an even distribution of the solvent concentration, the top was made to the shape of a pyramid, and four exhaust ports were provided at the corners from which animal cages were kept apart. The experimental results of the exposure to toluene gas at a desirable concentration of 2000, 1000 or 200 p.p.m. 8 hours a day, for 7 months, proved that, except only a preparatory inspection of the apparatus before the exposure and necessary ajustment every four days, the exposure can successfully be continued with deviations within 20% of the desired concentrations. Practically, the more frequent adjustments will make the smaller deviations in the gas concentration. The distribution of the gas concentration in the chamber was pretty satisfactory, other noxious factors than the solvent gas being negligible.

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From the viewpoint of occupational health, investigations on the salmon-trout fishery in the North Pacific Ocean were carried out during April to August in 1964, examinees being 22 members of the crew of the A-maru, an independent sail fishing boat operating from a home port. Many of them were found to have a cardiac hypertrophy and, at the end of the fishing period, they showed decrease in the body-weight, tendency to anaemia, hearing loss, increase in CPT (cold pressure test) swing degree, lowering in TAF (target aiming function), increase in the incidence of occupational diseases as contact dermatitis (so-called Shio-kabure) and tendovaginitis, and noticeable increase in hyperacidity. It is considered that these symptoms came from, on the one hand, the increase of the mental and physical stresses due to over-time and over-load work of fishing, confined mode of life in a rather abnormal environment of a boat, continued psychological strain under international control of the salmon-trout fishery in the North Pacific Ocean, and, on the other hand, they were caused by the unbalanced nourishment unavoidable in a long-term sailing. Fishermen of older ages tended to be worse in health status. This fact may be discussed with regard to the recommended age for fishing work or the premature aging in fishermen. It was an indication of the level of their knowledge about the prevention of veneral diseases that 23% of the crew were positive in the Wassermann reaction. Almost all members of the crew were married, so the conjugal infection of the diseases and consequently, the influences on the next generation should be a matter of concern.

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