In occupational lead poisoning neurological symptoms, especially minor degrees of peripheral nerve damage, seem to be still common, although severe one such as lead palsy is now rare in clinical practice. Neurological and electrophysiological investigations were performed in 59 workers handling lead in 5 factories. The duration of the exposure was from less than one year to 43 years. Their age distribution was 18 to 64 years, with a mean of 38.4 years. Most of them had some of such complaints as joint pain, lumbago, muscle pain, dizziness, fatigue of lower limbs and so forth. Various nerve conduction measurements were done at median and tibial nerve segments of one side for every worker. Routine electromyography revealed neurogenic changes such as slight decrease in NMU, polyphasic potentials and occasional giant spikes in 39 cases. MCV reduced in 6 cases in the median nerve (*) and 2 cases in the tibial nerve. Sensory nerve conduction velocity was reduced in 8 cases in the median nerve. In 2 cases no sensory action potential could be recorded from the median nerve. Mixed nerve conduction velocity was significantly decreased in 11 cases for the median nerve segments (*) and im 9 cases for the tibial nerve segment.The results mentioned above suggested that there was an evidence of abnormality of peripheral nerve functions in the lead workers without marked clinical neurological signs. Besides, present electrophysiological examination revealed moderate disturbances not only of the sensory nerves but of the motor nerves in most cases. There did not appear any association between the electrical findings and urine lead levels or length of exposure to lead. ((*) The meam conduction velocities of both nerves were significantly lower in the group of lead workers as compared with the age-matched control group. p<0.01.)

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We have studied on the properties of ALA-D, and intended to develop a more useful test for evaluating the effect of lead-burden. The enzymes from lead workers and normal subjects show identical properties after heat treatment. The depressed activity by lead-burden could be evaluated by means of calculating the ratio of non-heated enzyme activity to heated enzyme activity, namely value for heat effect “VHE” expressed as a percentage. Determination of VHE is superior to the measurement of ALA-D activity in order to differentiate relatively law lead-burdened subjects from non-exposed subjects.

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Synthetic detergents are becoming to be consumed largely in domestic life and in working places with the development of petroleum industry in Japan. And, numbers of housewives who complained of eczema of hand and visited the hospital have recently increased. Though the relationship between the use of synthetic detergents and the prevalence of eczema of hand in housewives had studied by some doctors, it has not been made so clear yet.
Therefore, health disorders, mainly those of hand skin, in the workers using large amount of synthetic detergents were studied. Observed subjects were 93 female workers for school lunch at 33 schools in Y city, and the control were 85 female teachers, clerks and others in Y city.
The results are as follows :
1) The workers for school lunch had significantly more complaints of roughness, thinness or loss of fingerprints, stiffness and exanthema of hand skin than the control. Disorders of hand skin in the workers for school lunch were characterized mainly by non-inflammatory changes such as hyperkeratosis, crevice formation, desquamation, etc. However, erythema of hand including those around nail were also found significantly more in the workers for school lunch than in the control. The disorders of hand skin in the workers might be caused mainly by contact with synthetic detergents for a long time, but they might have been deteriorated by mechanical and other chemical stimuli at washing tablewares or other hand works.
2) Disorders of hand skin were improved in summer and became worse in winter in both groups, but this tendency was more remarkable in the school lunch workers than in the control. And percentage of the workers for school lunch who had no complaint of hand skin during all seasons was only 9.7%, while that of those in the control was 35.3%.
3) Symptoms and signs of hand skin in some workers for school lunch were improved 3 weeks after soap was used instead of synthetic detergents, and the differences between both groups became not so clear. In spite of this, this might be due to insufficient data, and a further study is desirable.
4) In order to prevent the workers from disorders of hand skin, the working conditions should be so improved that the workers would not directly contact synthetic detergents or less toxic substance should be substituted for them.
5) The workers for school lunch had significantly more complaints of stiffness or dullness of shoulder, pain of neck and pain of the back than the control as revealed by the questionnaire compiled by the Committee on Neck-Shoulder-Arm Syndrome in Japan Industrial Health Association. It is thought that operations of washing the tablewares in the school might impose a heavy burden to shoulder, neck and the back of the workers.

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It is widely known that the causative substance of “Minamata disease” was methylmercurials concentrated in the fishes and shellfishes. It has been also reported that the organs of the patients as well as those of cats, fishes and shellfishes which suffered from the same disease contained high concentrations of selenium in addition to methylmercurials.
But the investigation of the modifying effect of selenium compounds on the toxicity of methyl-mercurials is not necessarily ample and the study on the distribution of methylmercurials and selenium compounds in the body exposed to them simultaneously is almost scanty. The present paper describes the distribution of radioactive mercury (²⁰³Hg) and selenium (⁷⁵Se) in mice after the simultaneous exposure to methylmercuric chloride and sodium selenite.
In order to determine radioactive mercury and selenium, the simultaneous-discriminative determination method using a Ge (Li) solid state detector with a multi-channel pulse height analyzer was established and used.
Since the acute lethal dose of sodium selenite in mice have not yet been known, the lethal toxicity test was carried out in advance to fix the standard for the dose used in the present study. I. Lethal effective dose 50% (LD 50) of sodium selenite in mice.
Thirty five mice (ICR-JCL strain, male, 12w., mean ±SE of body weight=37.0 ±2.3g) were equally divided into five groups. To each group of mice a single respective dose of 0, 3.0, 4.8, 7.7 and 12.3mg Se/kg of sodium selenite was injected subcutaneously. Observation period was one week. As a result the approximate value of LD 50 was 6 mg Se/kg and the dose-response curve seemed to rise sharply around LD 50.
II. Simultaneous-discriminative determination method of radioactive mercury (²⁰³Hg) and selenium (⁷⁵Se).
The Ge (Li) solid state detector and the pulse height analyzer with 1024 channels were used for determining the radioactivity of ²⁰³Hg (γ : 0.279 MeV) and ⁷⁵Se (γ : 0.280 and 0.265 MeV). The calibration curve of energy vs. channels, the relationship between the sample size and the cpm, the limits of determination and the percentage of the cpm of the γ-ray (0.280 MeV) to that of the γ-ray (0.265 MeV) of ⁷⁵Se were examined. The method of calculation of the radioactivity from the record was also described.
Consequently the samples of which both the radioactivity itself and the percentage of the cpm of the γ-ray (0.280 MeV) to that of the γ-ray (0.265 MeV) of ⁷⁵Se showed the constant values with some variance and of which the sample size (cross section) was almost the same as that of the tissue used for the present experiment could be measured and gave us reasonable data. III. Distribution of ²⁰³Hg and ⁷⁵Se in the body.
Forty five mice (ICR-JCL strain, male, 11 w., mean ±SE of body weight=32.1±1.9g) were equally divided into three groups which were treated with methylmercuric chloride alone, both methylmercuric chloride and sodium selenite, and sodium selenite alone, respectively. To each group of mice labeled compounds of methylmercuric chloride (CH₃²⁰³HgCl, 125 μCi/1mg Hg/1kg of body weight) and/or sodium selenite (Na₂⁷⁵SeO3, 132 μCi/0.5mg Se/1kg of body weight) were injected subcutaneously. At the specified time mice were killed after collecting blood by heart puncture followed by removing the small intestines including their contents, brain, liver and kidneys. Radioactivity of mercury and selenium was measured according to the method described above.
The results and discussion are as follows :
1. In regard to the concentration and the elimination rate of mercurials in the liver, kidneys, small intestines and blood, no obvious difference was detected between the group treated with the two compounds and the

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