Xylene is a neurotoxic organic solvent widely used in industry. However, the neurochemical mechanism of its action on the central nervous system is to date relatively unknown. In this work, the effect of subacute xylene exposure on met-enkephalin like immunostaining in different brain regions is described. Acute treatment with xylene generates a reduction in immunostaining for met-enkephalin in the globus pallidus, the olfactory tubercule and the hypothalamic medial preoptic area, without changes in the parietal cortex, caudatus-putamen and the central amygdaloid nuclei. It is suggested that enkephalins could play a role in xylene neurotoxic mechanism in the brain.
With a view to developing a method of evaluating mental work stress, a paced calculating task (addition and subtraction of two two-digit figures) with eight grades of workload (20%-160% of work capacity) was assigned to 21 male and 20 female students. Using a VDT, subjects performed the task and psychological and physiological measures of mental activity (intellectual activity, feeling, arousal level) were determined. Occipital midline (Oz) β2 (20Hz-30Hz) amplitudes regressed linearly against workloads, with a marked rise observed at overload levels (above 100% workload), though the number of correct responses did not increase at such levels. Error rate, subjective task difficulties, and feelings (unpleasant, tense, excited) were proportional to workload and closely correlated to each other. Blood pressures and heart rates increased slightly in proportion to workload, with a correlation between them. Feelings were presumed to be not particularly intense even at overload levels. Regression coefficients of error rate, excitement level, and Ozβ2 amplitude were larger in females than males. Based on the results, it was inferred that females might sustain somewhat more severe work stress than males. Critical flicker frequencies decreased over time. The criteria for evaluating heavy and excessive mental work stresses were deduced from the Ozβ2 amplitudes, which best reflected intellectual activity, and from the critical flicker frequency, which is related to arousal level.
In this report we describe yearly changes in pneumoconiosis patients and pneumoconiosis progression in each industry in Japan, using statistics of Ministry of Labour based on the results of pneumoconiosis examinations performed at plants in accordance with the Pneumoconiosis Law. We found that the number of workers exposed to mineral dust decreased yearly. The number of subjects with positive findings, the number of new cases with pneumoconiosis, the ratio of positive findings, and the incidence rate of pneumoconiosis also decreased. In particular, the number of subjects with positive signs of pneumoconiosis clearly decreased. A similar tendency was seen in the number of cases including voluntary applications. Industry-wise, however, there was a large difference among the industries. The ratio of pneumoconiosis with complications, along with the progression ratio, decreased. Subjects with progressed pneumoconiosis decreased annually, exhibiting less-serious signs and symptoms. There have been reports with a different view about the general trend of pneumoconiosis. We examine and discuss the cause of discordance between the studies.
Stress has become an increasingly important occupational health matter in Japan. We found that noise exposure, 6kHz wave and its higher harmonics at the sound pressure level of 112dB, induced typical audiogenic seizures in the MRL/l mouse strain. The seizures are often fatal. Wild running preludes to seizures. Inhibition of wild running by restricting animal's activities successfully prevented the seizures, suggesting that an excessive physical load is a necessary step. The present finding indicates that MRL/l mice may be a useful model for human sudden deaths after excessive work loads.
In order to find out whether dust respirators are properly used among lead workers in small scale manufacturing companies of lead pigments and stabilizers, a questionnaire survey was carried out for 141 lead workers. The questionnaire consisting of 7 items of questions including selection, use, maintenance, storage and instruction of respirators was distributed to all 141 workers. This survey revealed that 22% of the total workers wore unauthorized dust respirators, and that 73% used a knitcover. Instruction by health supervisors of how to use and where to store the respirators was found to be effective for inspection of valve and a proper place to store dust respirator. However, the result that significantly large percentage of workers used the knitcover following the health supervisors' instruction can be taken to indicate that health supervisors should be given more precise information on deteriorated face-sealing of the respirator facepiece with the knitcover.