To investigate the possible effects of long commuting time and extensive overtime on daytime cardiac autonomic activity, the short-term heart rate variability (HRV) both at supine rest and at standing rest of 223 male white-collar workers in the Tokyo Megalopolis was examined. Workers with a one-way commute of 90min or more exhibited decreased vagal activity at supine rest and increased sympathetic activity regardless of posture, and those doing overtime of 60h/month or more exhibited decreased vagal activity and increased sympathetic activity at standing rest. These findings suggest that chronic stress or fatigue resulting from long commuting time or extensive overtime caused these individuals to be in a sympathodominant state. Although these shifts in autonomic activities are not direct indicators of disease, it can be hypothesized that they can induce cardiovascular abnormalities or dysfunctions related to the onset of heart disease. Assessment of the daily and weekly variations in HRV as a function of daily life activities (such as working, commuting, sleeping, and exercising) among workers in Asia-Pacific urban areas might be one way of studying the possible effects of long commuting time, and extensive overtime, on health.
The aims of the present study were to identify correlates of alanine aminotransferase (ALT or GPT) and aspartate aminotransferase (AST or GOT) activities among a healthy working population aged 18-39, and to discuss liver transferase abnormalities. Subjects included 1, 009 employees of a company in Fukushima, Japan. Pregnant women, employees exposed to organic solvents, and employees with a history of liver diseases were excluded. Serum ALT and AST levels were measured by an enzymatic method. Other information including BMI, job type and lifestyles was recorded. Mean ALT and AST levels were significantly higher for males than females (P<0.001). Multiple linear regression analysis revealed that sex and BMI explained 45% and 31% of the variability in ALT and AST, respectively. The prevalence of abnormal ALT levels (>40 IU) was 16.3% for males and 0.4% for females. Sex, BMI, and shift work were independently associated with abnormal ALT levels by logistic regression analysis. It is concluded that ALT and AST levels are well-correlated with sex and BMI, and that abnormal liver transferase activity is prevalent in male employees but rare in females, suggesting that liver function tests should be introduced for male employees under 40 years of age.
A survey of solvent was conducted for 196 unit work areas in 95 plants in 1994 to 1996 in Hiroshima Prefecture, Japan. The survey had been repeated every 6 months (i.e., twice a year) during the 3-year period. Sampling and analysis of the solvent vapors were carried out after national protocols set by the regulation. Toluene was most frequently detected regardless of the type of solvent work (except for degreasing), whereas the second- and the third-most common solvents varied depending on the type of solvent works. Among chlorinated hydrocarbon solvents for degreasing, dichloromethane was most widely used. Solvent concentrations were generally low as none of the median concentrations exceeded corresponding Administrative Control Levels set by the regulation, either individually or even when the assumption of additiveness was applied. Among the 1176 cases analyzed, 80% of the unit work areas were evaluated as adequate (i.e., classified as Class I). Furthermore, about 57% stayed in Class I throughout the 3 years, suggesting that solvent exposure conditions were generally quite stable. In regulatory evaluation by classification, A-sampling was decisive in most cases, whereas the role of B-sampling was limited.
To clarify the function of Pb-binding protein and the interaction between lead and selenium in human erythrocytes, the following experiments were performed. (a) blood from a man who has not been exposed to lead occupationally, (b) blood from lead-exposed workers and (c) blood from control subjects working in the same plant were used. (a) was incubated with Pb and/or Se. Hemolysates of rinsed erythrocytes were applied onto a Bio-gel A 1.5m column and eluted by 40 mM Tris-HCl buffer (pH 7.0). As the results, (1) Pb in erythrocytes was found in ALAD fraction. When Pb was added in vitro at 1.25μM of final concentration, Pb content of ALAD fraction increased and the other Pb-containing fraction appeared at the position of a smaller molecular size than that of Hb fraction. When Pb dose added was increased to 2.5 or 10μM, Pb contents in the newly appeared fraction was larger than that in ALAD fraction. The affinity of Pb with the protein in the new fraction was weak, and Pb was released from the protein by ultrafiltration. (2) There were main and sub-peaks containing Pb in erythrocytes from Pb-workers; the former was ALAD fraction and the others were smaller molecules than ALAD. The peak of Pb observed with the blood from a worker who has worked at the same plant for more than 20 years (chronic exposure) corresponded with the new peak which appeared in vitro Pb exposure. (3) As to the interaction between Pb and Se, there was no effect of Se added in vitro on the position of Pb-containing fraction and on Pb amounts in the chromatographic profile. When Se was incubated with blood, however, coexistence of Pb made Se concentration in erythrocytes high compared with the case of Se alone.
Plasma lead (Pb-P) from workers were distributed in two main fractions: a protein bound fraction and low molecular weight fractions. Lead mobilized into plasma by CaEDTA was mainly observed in the low molecular weight fraction corresponding to lead disodium ethylenediamine tetraacetic acid (PbEDTA). The peak levels of Pb-P was attained around 1.5 and 2.5 hours after the start of CaEDTA injection. Pb-P and blood lead levels (Pb-B) at 2h after the injection were 4.26 (± 2.84) and 0.96 (±0.27) fold of the initial levels just before the injection. Pb-P concentrations at 2 hours after the start of CaEDTA injection (MPb-P) were well correlated (r=0.740) with amounts of lead excreted in urine for 24h thereafter (MPb-U). log MPb-P as well as log MPb-U were correlated with Pb-B (r=0.765 and 0.817, respectively). Correlation coefficients of lead body burden (MPb-P or MPb-U) vs the logarithms of the effect indices (delta-aminolevulinic acid (ALA) dehydratase, ALA in urine, coproporphyrin in urine, and erythrocyte zinc protoporphyrin) were higher than the correlation coefficients of exposure indices (Pb-B or Pb-U) vs the logarithms of the effect indices. Thus the biological effect monitoring is significant and reliable for evaluating the functional components of lead body burden (MPb-P or MPb-U).
Acute exposure to high doses of toluene can generate respiratory depression. However, neurotoxic mechanism of its action in the brainstem is not completely clear. In this work, acute, but not subchronic, exposure of rats to toluene increased leu-enkephalin immunostaining in several myelencephalic nuclei implicated in cardiorespiratory control. Due to the physiological role of enkephalins in the central regulation of breathing, it is suggested that the enkephalinergic system could play a role in neurotoxic respiratory depression induced by high dose acute toluene exposure.
Age-adjusted standardized mortality ratios (SMRs) and life tables in male occupational groups for all causes and major diseases such as malignant neoplasm of stomach and lung, cerebrovascular disease, ischemic heart disease, traffic accidents and suicide was compared between Japan and Great Britain. Except for traffic accidents and suicide, males in higher employment grades had lower SMRs which had also been found to be related to other social class indicators such as perinatal death rate, the frequency of work absence and current smoker's rate. Occupational differences in mortality rates for major diseases became smaller with advancing age in Great Britain but not necessarily in Japan. The present authors concluded that inequalities in socio-economical factors were more likely to be the primary factors for survival, and that selection such as occupation and occupation-related lifestyle might still be an important factor for the inequalities. These inequalities were more obvious in Japan, where a life expectancy was, however, best in the world.
Silica may act as a stimulator of pulmonary inflammation and fibrosis. The effect of silica on phospholipase D (PLD) activity assayed as accumulation of [3H] phosphatidylethanol ([3H]PtdEt) was examined in[3H]palmitic acid-labeled primary cultures of rat alveolar macrophages. Silica induced a rapid accumulation of[3H]PtdEt in a time (0, 15, 30 and 45min)-and concentration (0.5, 1.0, 2.5 and 5.0mg/ml)-dependent manner indicating PLD activation. This silica-stimulated PLD activity was attenuated by the pretreament with calcium chelator ethylene glycol-bis(β-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) or/and 1, 2-bis(2-aminophenoxy)ethane-N, N, N, N-tetraacetic acid acetoxymethyl ester (BAPTA/AM) (EGTA: 54.3±8.6%, BAPTA/AM: 67.5 ±7.8% and EGTA+BAPTA/AM: 35.8±2.9, respectively). Also, silica-induced PLD activation was partially inhibited by the pretreatment with nonspecific phospholipase C (PLC) and PLD inhibitor (neomycin; 66.4±4.8%) or specific PLC inhibitor (U73122; 70.8±4.6%). Sphingosine as a protein kinase C (PKC) inhibitor did not change silica-induced PLD activity indicating that PKC might not play a role in PLD activation by silica. Based on these results, we concluded that a silica-stimulated phospholipase D activity is present in the rat alveolar macrophages and is predominantly regulated by PLC-mediated intracellular calcium.
To investigate the relationships among the amount of job stressors, self-reported sleep quality, and daytime autonomic activities, a questionnaire survey was conducted for 223 healthy male white-collar workers, and their short-term heart rate variability (HRV) was also examined. Half of the subjects complained of nightly poor sleep quality. Self-reported poor sleep quality was associated with a qualitative aspect of job stressors characterized by high amounts of “job difficulty”, less amounts of “achievement in job”, and less amounts of “support by colleagues”, and also with high amounts of personal distress and difficulty in changing their mood. Those who complained of poor sleep quality exhibited sympathetic predominance and reduced heartbeat intervals at standing rest, although job stressors was not correlated to HRV. These results suggest that their job stress disrupts nightly sleep, and also that their insufficient sleep at night causes daytime sympathetic predominance. However, the amount of job stressors was not directly associated with HRV. Further studies should focus on the relationships among chronic job stress, the satisfaction of sleep demands, and the daily and long-term variation in cardiac autonomic activities.
Correlations of lethal doses of industrial chemicals between oral or intraperitoneal administration and inhalation exposure in rats and mice were investigated. LC50 values for inhalation exposure and LD50 values for oral and intraperitoneal administration were obtained from the Registry of Toxic Effects of Chemical Substances. LC50 and LD50 values were plotted on ordinate and abscissa, respectively, using logarithmic scales. A correlation coefficient of r=0.624 (n=146, p<0.001) was obtained for LC50 (ppm) and LD50 (mg/kg) values with oral administration (oral LD50) in rats. This correlation was improved by converting the units of LC50 from ppm to ppm h (cumulative dose), and by converting the units of LD50 from mg/kg to mmol/kg. The correlation coefficient was r=0.742 when ppm*hr and mmol/kg were adopted for LC50 and LD50, respectively. A similar improvement in correlation coefficients by the same unit conversion was also observed between LC50 and LD50 with intraperitoneal (i.p.) administration (i.p. LD50) in rats. Correlations between LC50 and oral LD50 in mice were also improved by the same unit conversion. The correlations between LC50 and i.p. LD50 were higher than those between LC50 and oral LD50 both in rats and mice. In these correlations, coefficients obtained in rats were greater than corresponding coefficients in mice. We calculated equations to estimate LC50 values accompanied by confidence limits from oral or i.p. LD50 values.
The advent of compact and lightweight portable personal computers has offered its users mobility. Various sizes of PC-FPDs can now be seen in the occupational setting as an alternative to the desktop computers. However, the increasing popularity of this relatively new technology may not be without any accompanying problems. The present study was designed to evaluate the use of PC-FPDs in terms of postural changes, muscle load, subjective complaints and performance of the subjects. Ten subjects, 5 males and 5 females, were asked to perform a text-entry task for 5 minutes using each of the 5 types of personal computers-1 desktop and 4 PC-FPDs of various sizes. Results showed that the posture assumed by the subjects while using the PC-FPDs was significantly more constrained than that assumed during work with the desktop computer. Viewing and neck angles progressively lowered and the trunk became more forward inclined. The EMG results also revealed that the activities of the neck extensor in PC-FPDs were significantly higher than in the desktop computers. Trends of increasing discomfort and difficulty of keying with the use of smaller PC-FPDs were noted. Performance was significantly lower for smaller PC-FPDs. This study shows that PC-FPDs have ergonomic attributes different from the desktop computer. An ergonomic guideline specific for PC-FPDs users is needed to prevent the surge in health disorders previously seen among desktop computer users.
A severe earthquake of magnitude 7.2 hit the west part of Japan on January 17, 1995. A part of the Shinkansen railway, which is one of the most popular high-speed mass transportation systems in Japan, was seriously damaged by the earthquake. About 80 days later, the Shinkansen service was resumed but complaints about vibration due to the passing Shinkansen increased rapidly among residents near the tracks. This paper reports the results of two investigations that were carried out in both stricken and non-stricken areas to determine the cause of complaint. In the first investigation, the ground vibration propagation induced by passing trains was measured. In the second investigation, questionnaires were distributed to the people living near the Shinkansen tracks. As a result, it was found out that the vibration levels before and after the earthquake were almost the same at most measured points in the stricken area. It was also found that the vibration levels in the stricken area and a non-stricken area were almost the same within 50m from the Shinkansen tracks. However the results of the questionnaire survey showed that people's nuisance due to the vibration in the stricken area was clearly greater than that in the non-stricken area. This inconsistency was explained using the “category judgment method”, which is generally used to determine the relationship between a physical stimulus and psychological reaction. According to the results of this analysis, the vibration level, at which 50% of the inhabitants complained about Shinkansen vibration, was approximately 54dB in the non-stricken area and 50dB in the stricken area. This result suggests that the people who experienced the severe earthquake became 4dB more sensitive to the Shinkansen vibration than the people living in a non-stricken area despite the fact that this investigation was carried out 10 months after the earthquake struck.
The influence of 2-bromopropane, an alternative to freon, on ovulation was examined using superovulation induced by pregnant mare's serum gonadotropin and human chorionic gonadotropin (PMSG-hCG) treatment. Three groups of mice were injected intraperitoneally 8 times with 2-bromopropane (2-BP) at 500, 1, 000 or 2, 000mg/kg and were induced to ovulate by PMSG-hCG treatment. Injection of 2-BP caused the number of ovulated ova in the 1, 000mg/kg and 2, 000mg/kg groups to decrease remarkably. Uterus weight was also decreased in the 2, 000mg/kg group on the terminal day of the experiment. This result was consistent with cases of human intoxication in which reproductive toxicity was observed.
A male worker who handled thallium-containing raw material for glass manufacturing over a period of four years complained of alopecia, abdominal pain, diarrhea and tingling in the four extremities. Neurological examination of this patient revealed signs of mild glove-stocking-type polyneuropathy. Lower sensory nerve conduction velocity of the median nerve in the right hand than in the left hand suggested that conduction function in the dominant hand was reduced. The thallium content of the hair, as determined by an ICP-MS method, was 20ng/g for the patient and 576ng/g for his successor in the time of 32 months and 13 months, respectively, after they had ceased their glass production work. Those levels of thallium exposure were considered high, compared with the control levels so far reported. The clinical course of signs and symptoms, neurophysiological findings and thallium content of hair suggested that the patient suffered from chronic poisoning due to occupational exposure to thallium-containing dust.