Interest in subclinical lead neuropathy has recently intensified. In this paper, we aim at reviewing current methods for the diagnosis of peripheral neuropathy due to lead absorption. Neurological diagnostic methods and blood lead measurement are essential for the diagnosis of clinical lead neuropathy. However, for the diagnosis of subclinical lead neuropathy, the measurement of nerve conduction velocity is considered to be most sensitive and reliable on the group basis. But, on the individual basis, the conduction study is not sensitive enough because of small changes in the velocity often ranging around the lower limit of “normal” values.

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Free silica content in airborne dust was measured with a modified procedure collecting sample dust on glass fiber filter and heating the dust together with the filter in phosphoric acid. The insoluble phosphoric acid residue of the glass fiber filter used by us was of small amount. Fifteen mg of dust was enough to determine its free silica content correctly.
On dust collected at pottery and foundries works, satisfactory coincidence was found between the values of free silica content by our procedure and by X-ray diffraction. It can be concluded that this is a reliable method for determination of free silica content of airborne dust as well as of deposited one.

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Pest control operators usually spray pesticides in small areas such as a kitchen in a restaurant and are exposed to various pesticides, especially those of the organophosphorus (OP) type. In order to evaluate their occupational exposure to OP pesticides during the work, OP pesticides in blood and alkyl phosphate metabolites in urine of these operators were analyzed and the relationship between pesticide exposure and analytical results were studied.
OP pesticides in blood were analyzed by gas chromatography with flame photometric detector (FPD-GC) after separation of phospholipid in blood with silicagel column chromatography. OP pesticides were not detected in any blood samples (the limit of detection was 1 ng/ml).
Dimethylphosphate (DMP) and dimethylthiophosphate (DMTP), being urinary metabolites of OP pesticides, were analyzed by FPD-GC after benzyl derivatization. This method eliminated interfering peaks in gas chromatograms. The ratio of two isomeric derivatives of DMTP was found to be constant. Both DMP and DMTP of the exposed group were significantly higher than those of the non-exposed group, DMP being higher than DMTP. The ratio of DMP to DMTP in the fenitrothion-dichlorvos-exposed group was significantly higher than that in the fenitrothion-exposed group. It was considered that the ratio might reflect a result of pesticide exposure. The urinary metabolites of OP pesticides tended to become lower with the lapse of time since the last exposure. However, small amounts were detected in a few samples even 5 days after the last exposure.

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There have been many studies of thermographic diagnosis of vibration disease, but few of them seem to have discussed tie-tamping machines as a cause. This study focusses on thermographic diagnosis of vibration disease in tie-tamper operators of the Japanese National Railways. In the diagnosis the subject's both hands were immersed in water at 10 degrees C for 3 minutes before being examined. Variables such as season, age, type of vibration tool used and total operating time were considered. These were selected as outside variables and thermographic results as dependent variables, in Quantification Method II. Season and confirmation of vibration disease were found to have a relationship to thermographic scaling, but no such relationship was found for age, type of vibration tool used, or total operating time.
A cross-analysis of variables confirmed the relationship with season, and revealed that there were fewer confirmed cases of vibration disease in spring and summer than in fall and winter. It was finally concluded that thermographic analysis is more reliable in colder weather.

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In the process of “tatami” mat production, from cultivating to weaving, rush farmers are exposed to “sendo” (dyer's earth) dust using it to prevent fading of the “tatami” mat color. It has been found that the workers tend to develop a relatively early stage of pneumoconiosis after about 20 years of this work.
In 1980, 51 male (58.6 years old) and 37 female (54.4 years old) rush farmers, some of whom were previously examined in 1970, were re-examined for lung disorders.
Chest X rays in the 1980 showed, 49.0% of males and 62.2% of females over 1/0 according to the 12 point profusion scale with irregular small opacities being dominant, a significant increase in the prevalence rates of pneumoconiosis compared with 1970 values (p<0.01 for both males and females). A relatively high prevalence of respiratory complaints and/or lung function impairment was also found. However, there were no severe cases and no significant changes were seen to have occurred during the seventies by those tests. It was also observed that increases in lung disorders during the decade were more common in the female workers.
These findings suggest that the pathogenesis of rush farmer's pneumoconiosis might be in the histological changes of bronchial and/or alveolar walls by the deposition of “sendo” dust.
The present study revealed that the lung disorders in the rush farmers may be associated with longterm inhalation of “sendo” dust, and the introduction of more suitable dust control measures in that processing must be actively pursued in the near future.

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In order to clarify the long-term effect of tunnel work on the health of its workers, we examined its cause-specific mortality pattern.
The subjects were 418 males who died after the age of 30 in 1977 in the southern part of Oita Prefecture, where many men come and work away from home as tunnel workers. Death certificates, 418 in number, presented to the health center were used to examine the causes of death. Occupational careers and life histories of the subjects were obtained by interviewing their families or relatives in 1980. The interviews were successfully carried out with 356 subjects (85.2%).
The subjects were divided into two groups. One group was consisted of 73 males who had engaged in the tunnel work (tunnel workers) and the other was of 283 males without experience of tunnel work (others). Proportional mortality ratio (PMR) and proportional mortality classified by age were compared between the two groups. The mean ages at death were also compared among these two groups and all Japanese males over 30 years of age.
The results were as follows.
1) The proportion of the deaths of “tunnel workers” among the total deaths in the area surveyed was correlated to the regional rate of tunnel workers and the distribution of pneumoconiosis due to tunnel work. These results show that many tunnel workers suffering from pneumoconiosis had returned to their home area before they died.
2) Excess deaths from the ICD category I; infective and parasitic diseases (000-136), tuberculosis (010-019) and silicotuberculosis (010) were found among the “tunnel workers.” These excess deaths covered a wide range of age. No excess was observed among the “others.”
3) The mean age at death of the “tunnel workers” was lower than that of the “others” and also that of all Japanese males.
4) A dose-response relationship was observed between the PMR for silicotuberculosis (010) of the “tunnel workers” and the duration of the tunnel work.

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Forty-one dust-and-ozone-exposed and 37 nonexposed workers, belonging to the Research and Development Division of a photo-copier manufacturing industry, were examined to assess the effect of the exposure to carbon, iron and resin dust and ozone in the air of the work environment by means of questionnaires on their physical condition, smoking habits and exposure history by interview, chest X-rays, testing of ventilatory functions, transcutaneous Po₂(tcPo₂) test and H₂O₂-induced hemolysis test. The following results were obtained.
1) Respirable dust concentrations in the air of the work place were 0.1-1.0 mg/m³, total dust concentrations 0.2-2.0 mg/m³, and ozone concentrations 0.004-0.06 ppm (0.008-0.12 mg/m³).
2) According to the Japanese Classification of Radiographs of Pneumoconioses, the exposed workers showed a higher rate of profusion 0/1 and over, and category 1 and over (1/0 and over) than the nonexposed workers.
3) Ventilatory function testing revealed no difference between exposed workers and nonexposed workers, but small airway narrowing was suspected in smoking workers in comparison with nonsmoking workers.
4) Transcutaneous Po₂ showed no difference between exposed and nonexposed workers, between smoking and nonsmoking workers, and between any of the paired six combinations out of the four groups of workers, i.e., nonsmoking and nonexposed, nonsmoking and exposed, smoking and nonexposed, and smoking and exposed.
5) It was estimated by H₂O₂-induced hemolysis test that smoking and/or dust exposure, especially long-term exposure, gave rise to aggraviation of fragility of the erythrocyte membrane by lipid peroxidation with ozone or active oxygen produced by the reaction of dust and alveolar macrophages.
6) The questionnaire was considered indispensable to ascertain the workers' exposure history.
7) No worker in this work environment showed clinical signs indicating a need for medical care or home repose.
There results may indicate that in resolving the pathogenesis of pneumoconiosis further studies will be required on the prevalence rate of profusion 0/1 and over (or category 1 and over) under low concentrations of dust exposure and on the intrapulmonary reactions induced by low doses of dust exposure.

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