DDVP (dimethyl-dichlorovinyl phosphate) has been introduced into the sanitation field for mosquito and fly control. As the mass control method, its use in the form of aerosol by fogging machines has been widely adopted in Japan. Recently the fogging of DDVP indoors in window-closed buildings has become a new procedure for cockroach control in large cities. In this case, the inhalation toxicity will be the keen problem for spraying-workers as compared with that in spraying outdoors. The author tested the inhalation toxicity of DDVP aerosol for mice as reported in part I of present report and the effects of inhalation on the blood cholinesterase (ChE) in actual indoor fogging are reported in part 2. Part 1 The LC₅₀ of DDVP for mice in inhalating aerosol for four hours was found to be 310 mg/m³ in air. When the mice died during the experiment, ChE of brain was reduced to one-fourth of the normal level. Oximes such as 2-PAM or PAD were also effective for preventing poisoning. The concentration of 2-PAM necessary for reactivation in vitro of completely inhibited brain ChE was 10^-4 Mol. Rabbits were less resistant for inhalation test, at the lower concenration than mice LC₅₀ (being just equivalent to 70% of the latter) almost of all rabbits were dead. In that case the whole blood ChE was reduced to around 50% of the initial level. Part 2 Effects of fogging of DDVP oil solution were checked in four actual procedures, using 0.3 or 0.6% solution. Number of subjects were from four to eight, actual spraying hours were in the range from 8 minutes to 8 hours according to the size of buildings. Subjective complains were irritations in the conjunctiva, pharyngo-laryngeal pain, particulary in swallowing. These complains were likely to be caused by kerosene used as solvent and probably not by DDVP. Drop of ChE following the shorter work was negligible. Even in 8 hours' spraying the heaviest drop of plasma ChE was 25% to 30%, but that of red cell ChE remained within 7%, usually only 2∼3%. Among occupational sprayers engaged once or twice in a week in indoor spraying, no trend of decrease in the blood ChE was found.

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It has been found by Adams and by Begg that the catalase activity in the liver changes corresponding to the changes of the amount of sexual hormones, which was further ascertained by Hirokawa in the study of benzene poisoning. Recently, Ogura et al. have reported the mode of catalase reaction using a crystalline catalase with special reference to the inhibition of some substances such as KCN, HN₃, CH₃COOH, HCOOH and various phenols upon the catalase reaction. The results obtained by them may give a significant key to interprete the result obtained in the study of catalase activity in blood of poisoned animals benzene, toluene, butyl-tin chlorides and nitroglycol. The assay of catalase activity in blood was performed at pH 6.8 and 0°C and at the final state which is obtained by pretreating the buffered catalase solution (dilute blood with deionized water) with a small amount of H₂O₂ solution (2/2000M in final concentration) at 3 min. before the initiation of catalase reaction. 1. Catalase activity in blood of rats injected with 2.5 ml. of a mixed solution of benzene and sesame oil (4:1) daily decreased to 70% of that of control rats at the first week after the beginning of the injection, and recovered to the normal level at the 2nd week. At the 3rd week, it decreased again to 30%. Noteworthy is the fact that the values of control rats were constantly in the range of 100 ± 5%. When the enzyme solution obtained from the blood of poisoned rats was not pretreated with H₂O₂ solution, the reaction curve bended with time, whilst when the same enzyme solution was pretreated, the reaction curve became liner showing the constant inclination (Fig.2). These results may be interpreted as Ibeing due to an inhibitory effect of a certain poisonous substance accumulated in blood of poisoned rats upon the catalase reaction. This poisonous substance was extracted into a small amount of water by treating the blood of poisoned rats with acetone. 2. Catalase activity in blood of rats injected with toluene decreased as well as those injected with benzene (Fig.3). It was clarified that this decrease is caused by the inhibition of a poisonous substance accumulated in blood, which is not benzoic acid nor hippuric acid. 3. Catalase activity in blood of workers employed at a paint-spraying plant is shown in Fig.4. The mean value of workers of A-group employed after toluene was used as a main solvent instead of benzene was 80% of that of control, and that of workers of B-group employed before toluene was used was 60%. The values of control (10 examples) were in the range of 100±10%. 4. The catalase activity in blood of rabbits was more severely affected by the injection of tributyl-tin chloride than dibutyl-tin chloride (Table 3). 5. The catalase activity in blood of rabbits received 0.33g of nitroglycol per kg. of body weight decreased severely in several hours after the injection (Table 4). 6. The catalase activity in blood of workers in an explosives plant was lower than that of control (Table 5), and it did not recovered to the normal level even after two day's discontinuing of their work.

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