Industrial use of N, N-dimethylformamide (DMF) is increasing in recent years. The toxic properties of this substance are reviewed from the standpoint of industrial hygiene. Hepatotoxicity has been emphasized by many authors. Care should be taken against the skin absorption of DMF. N-methylformamide (MF) was identified as the major urinary metabolite of DMF. Measurements of MF in urine have been found effective as a means of biological monitoring of DMF exposure.

View full abstract

Cadmium has been thought to be carcinogenic for these ten years. The present author reviewed 98 papers on its carcinogenicity. Ten papers describing epidemiological studies on cadmium workers, re-evaluated by the present author, do not derive a solid conclusion that cadmium is carcinogenic. However, there still exists a certain probability that cadmium is a weak carcinogenic substance in the human, because of some data on chromosomal aberrations in cadmium workers, tumorigenesis at the site of cadmium injection in animals, and Leydig cell tumor formation in animals given subcutaneous injections of cadmium.

View full abstract

Over the years, a variety of uses has been found of organic tin compounds as fungicides, as stabilizers in plastics and for other industrial uses. The purpose of this article is to summarize and review the results so far obtained as to the analytical method for organotins in biological samples, the toxicity, metabolism, and biochemical and health effects of organotin compounds. 1) Many methods have been developed for analysis of organotin compounds by spectrophotometry, polarography, gas- or liquid-chromatography, etc. These methods, however, are mainly for analysis of organotins in standard solutions or in water, and are not suitable for organotin compounds in biological samples. Recently, we have developed several methods for analysis of various kinds of organotin compounds in biological samples. These methods are able simultaneously to separate and determine trace amounts (at nanogram order) of organotin compounds and their metabolites in the same biological samples. 2) Acute toxicity of organotin compounds which appeared on the literature are summarized. Trialkyl and triaryl compounds seem to be more toxic than the tetra-, di-, or mono-compounds of the same chain length. With an increase in the number of C atoms the toxicity of alkyl compounds decreases. Aryltin compounds are less toxic than alkyltin compounds. 3) Intestinal absorption sites for tetra-alkyltins are jejunum and duodenum, and those for trialkyltins are ileum and jejunum. A considerable amount of orally administered tetra- and trialkyltins of low molecular weights are absorbed, but only very little of the other organotin compounds seems to be absorbed from the gasterointestinal tract. Absorbed organotin compounds rapidly undergo dealkylation by the microsomal mono-oxygenase system dependent on cytochrome P-450 in the liver, brain or other organs, and the compounds and their metabolites distribute to the whole body, ultimately being excreted into urine, bile and faeces. The biological half life of organotin compounds in mammals is usually short, a half of the amount of tributyl- and triphenyl-tins deposited in the body disappearing in several days. A part of organotin compounds excreted into bile is demonstrated to have been absorbed from the intestine and to circulate in the body via enterohepatic circulation. 4) Specific effects of organotin compounds on the biological systems and health include disturbance of the structure and function of the central nervous system (interstitial edema of white matter), inhibited oxidative phosphorylation in mitochondria of cells, atrophy of the thymus and thymus dependent lymphoid tissues resulting in the dysfunction of T cells for immunity, inhibited enzyme activity, lesions in the liver and bile ducts etc., although some specificity is observed among species of animals and organotin compounds. Recently we found that a single oral administration of triphenyltin fluoride to rabbits induces transient diabetes and diabetic lipemia by inhibiting insulin secretion from morphologically normal pancreatic B-cells. Furthermore, the compound inhibits the aggregation of platelets in vivo and in vitro. 5) There are several reports on human organotin poisoning. The symptom indicates that organotin compounds affect mainly the central nervous system, producing cerebral edema. Other manifestations include irritation and inflammation of skin and mucous membrane, liver and bile duct dysfunction, keratitis, anosmia, etc. Health effects of organotin compounds are usually observed among workers exposed to the compounds and are the same as observed in experimental animals.

View full abstract

Occupational cervicobrachial disorders (OCD) among cash register operators have become an important problem since 1969. Some improvements of working conditions, such as, shortened operating time, adoption of worker rotation system and change of mechanical registers with heavy keytouches to electronic ones with light keytouches, were introduced in 1973-1974 at supermarkets at which the authors engaged in health care activities for the prevention of the disorder. Analysis was made for characteristics of 120 cash register operators of these supermarkets suffering from OCD during the period from 1972 to 1978, with special concern for differences before and after the improvement of working conditions. The subjects were divided into three groups by the year of their first consultation, A : 1972-1973, B : 1974 and C : 1975-1976. Patients of group A had engaged in cash register operation under the working conditions before improvements, and those of group C had engaged after improvements of working conditions. The authors observed that the incidence of the disorder among group C were less than that of group A, but the proportion of severe cases to all the patients were not changed. In group C more cases with chronic onset were observed than among the other two groups, and those patients with chronic onset took longer period for recovery compared with the other patients. In patients of group C compared with those of group A fewer complaints and muscle tenderness in the hands and fingers were noticed, and more cases with lowered back strength and cinesalgia of the neck were observed. The reasons for this were considered to be that the improvement of working conditions reduced the loads to the hands, but not much reduced the loads to the neck and the back.

View full abstract

Complaints, clinical findings and working conditions of the patients suffering from occupational cervicobrachial disorders (OCD) were discussed, with special reference to the prognosis of the patients. Subjects were 120 cash register operators with OCD engaged in supermarkets at which the authors participated in the health care activities for the prevention of the disorder. Thirtythree of them suffered from the disorder after getting well from the first onset. The authors discussed on the relationship between complaints and clinical findings of the patients and duration needed for recovery, the relationship between clinical finding and complaints of "the upper extremities" by the questionnaire of "complaints in daily life" and the relations of appearance of lowered grip strength to complaints and clinical findings. Case studies were also examined as to the influence of working conditions on the prognosis of the patients. Results were summerized as follows. 1. The severer the grade of OCD, the longer the duration needed to recover. 2. There were more complaints of arms, "the upper extremities" and "the legs", increased appearance of lowered back strength, cinesalgia of the shoulder, neck, and wrist joints, paresthesia, positiveness of Morley's test and muscle tenderness in the extensor muscles in the fingers, neck, back and so on among the patients with delayed recovery than among those recovered within 3 months. 3. Lowered back strength, muscle tenderness in the neck and in various sites of the body were observed more among the patients with many complaints of "the upper extremities" than among those without. 4. Lowered grip strength was not considered to be useful for early diagnosis of the patients. 5. Such working conditions, as carrying heavy goods and keeping upper extremities raised for a long time were considered to hamper the recovery of the disorder.

View full abstract

We previously reported that the working and health conditions of vibrating tool operators in an iron foundry were investigated in 1975 and vibration hazards were observed to occur frequently in workers operating chipping-hammers powered by compressed air. After that, we instituted medical treatment for the afflicted workers and improvement of working conditions in the foundry, and have performed annual medical examinations for four years. In this paper, the course of hygienic control and the change in the medical findings of twenty-four chipping-hammer operators are reported. 1. The following measures were taken to improve the working conditions of chipping-hammer operators and therapy for patients (Table 1) : (1) The operating time of vibrating tools, including chipping-hammer, was limited to two hours per day. The casting process was improved to diminish the flashes that are the objects of chipping-hammer operation. For the purpose of reducing the vibration transmitted to the operator, a servo-arm that has a servomechanism for the chipping-hammer was developed and introduced. (2) Infrared lamps in the foundry and air curtains at the doorway were installed for keeping the chipping-hammer operating area warm. A warm room was set up in the foundry for providing warmth during rest periods and protective clothing against the cold was provided. (3) Workers who displayed health disturbances by medical examinations were treated during the cold season from November to April by periodic visits to the clinic or extended hospitalization, or transferred to job without vibration exposure, according to their stage of disease. Preventive treatment with vasodilator and bubble bath was performed in winter for the chipping-hammer operators. 2. In order to estimate the effect of these countermeasures, annual medical examinations were conducted in March 1975, March 1976, April 1977 and March 1978. Such subjective symptoms as Raynaud's phenomenon, finger numbness, finger listlessness, heavy-headedness, forgetfulness, irritability and hearing disorder showed a tendency for improvement, but other complaints did not (Tables 2-4). The improvement of Raynaud's phenomenon is considered to be due not merely to the countermeasures but also to reducing the chance of provocation and therefore the countermeasures should not be overestimated as a factor of recovery of vibration hazards. Of the functional tests, a tendency for improvement was recognized in sensory functions and peripheral circulatory functions, but not in motor functions (Tables 5, 6). However, the course of recovery was not fast and some advanced cases, especially those using chipping-hammers for more than ten years, showed less improvement after hospital treatment (Table 7, Fig. 1). This indicates the importance of hygienic control which enables vibration hazards patients to have early diagnosis and treatment. Furthermore, in order to eradicate the vibration hazards in the cast metal industry, a drastic reform of the finishing process is considered to be necessary.

View full abstract

Male Japanese white rabbits were injected subcutaneously with methyl iodide (57 mg/kg body weight/day) on two successive days and their lipid metabolism was investigated 48 hr after the last injection, The plasma triglyceride levels increased from the preinjection average of 56.1 mg/dl to 246.0 mg/dl on an average, the individual values being greatly variable. Analysis of lipoprotein profile of plasma showed a significant increase of very low density lipoproteins (VLDL). Lypolytic activities in postheparin plasma did not change. However, rates of triglyceride secretion into plasma, measured by Triton WR 1339 injection method, were significantly higher in the animals treated with methyl iodide than in the controls. Histological investigation of the liver showed diffuse fat deposits in the hepatocytes without any destructive and inflammatory changes. The results indicate that hyperlipidemia and fatty liver of rabbits induced by methyl iodide is related to the elevation of triglyceride synthesis and its secretion in the liver.

View full abstract