Night work is becoming increasingly common. Unfortunately, humans are physiologically unsuited to inverted schedules, leading to negative consequences for shift workers, employers, and society. The circadian and homeostatic processes which govern sleepiness and alertness are improperly aligned for night workers. We review a number of laboratory studies designed to treat circadian maladaptation to night work by shifting the circadian clock with light, exercise, or melatonin. There is substantial evidence that bright light treatments can successfully overcome the circadian misalignments associated with night work. The evidence for the efficacy of non-photic synchronizers such as exercise and exogenous melatonin is equivocal. Nevertheless, our expanding scientific understanding of the nature of the problem has generated a promising range of options for shift workers.
Monocrotophos a organophosphate pesticide was administered orally at doses of 1.6, 3.3, 6.6, 10 and 13mg/kg body weight/day to normal virgin Swiss albino mice for 30 days. The vaginal smear and body weight of the mice were recorded daily and mice were sacrificed on 31st day. The ovaries from each animal was serially sectioned and stained for follicular studies. Estrous cycle was affected by showing a significant decrease in the number of estrous cycle and duration of proestrus, estrus and metestrus with concomitant significant increase in the duration of diestrus in all the treated groups, except with 1.6mg/kg body weight/day monocrotophos treated group. There were significant decrease in the small, medium, large and total number of healthy follicles and increase in the medium, large and total number of atretic follicles with 6.6, 10 and 13mg/kg body weight/day monocrotophos treatment. However, there were no significant change in the number of healthy and atretic follicles with 1.6 and 3.3mg/kg/bodyweight/day monocrotophos treatment. There was no change organs weight except for a significant decrease in weight of the ovary with 3.3, 6.6, 10 and 13mg/kg body weight/day and uterus and body weight with 10 and 13mg/kg body weight/day monocrotophos treatment. Interruption in estrous cycle, decrease in healthy follicles and increase in atretic follicles may be due to harmonal imbalance or toxic effects of monocrotophos, which adversely effects reproductive function, as it has also analgesic and sedative action.
By computerized static posturography with sway frequency analysis, subclinical effects of lead on postural balance was examined in 29 female workers (lead workers) employed at a glass factory for 3-17 (mean 7.9) years in Beijing, China, in relation to brainstem function assessed by brainstem auditory evoked potential (BAEP). Their blood lead concentrations ranged from 26 to 79 (mean 55.7) μg/dl; ages were 21-30 (mean 28) years. Control subjects, aged 22-29 (mean 27.0) years, were 14 healthy female workers at a textile factory located in the same district. With eyes closed, power of the sway of high (2-4 Hz) and low (1 Hz or less) frequencies in lead workers was significantly larger than that in controls; with eyes open, their power of the sway of low frequency was significantly larger (p<0.05). The multiple regression analysis showed that the power of high frequency sway with eyes closed and of low and high frequencies with eyes open were significantly related to blood lead concentrations in lead workers (p<0.05). On the other hand, no significant differences in BAEP latencies between lead workers and controls were observed. The low frequency sway with eyes open was significantly correlated with the high frequency sway with eyes closed in the lead workers. The pattern of changes in postural balance suggested that the anterior cerebellar lobe, vestibulo-cerebellar and spinocerebellar afferent systems were affected asymptomatically in female lead workers; the sway of vestibulo-cerebellar and anterior cerebellar lobe types were simultaneously affected by lead. It appears that a computerized static posturography with sway frequency analysis is useful technique for assessment of subclinical lead neurotoxicity.
Autonomic nervous function in response to cold was investigated in 21 patients with vibration-induced white finger (VWF) and 17 healthy controls of similar age, using power spectral analysis of heart rate variability. In a supine position, electrocardiogram and skin temperature of both index fingers were measured during immersion of right hand in cold water at 10°C for 10 minutes. Autonomic nervous activity was evaluated from the power of the low-frequency component (LF: 0.02-0.15 Hz), the high-frequency component (HF: 0.15-0.40 Hz) and the ratio of the LF to the HF power (LF/HF ratio). The LF/HF ratio, an index of sympathetic nervous activity, significantly increased during the immersion in the VWF patients, but did not significantly increase in the controls. The LF/HF ratio was then significantly greater in the patients than in the controls during the first 1-2 minutes of the immersion. The HF power related to parasympathetic nervous activity did not change significantly in either group. Finger skin temperature of the immersed right hand was significantly lower in the VWF patients than in the controls during the last five minutes of the immersion and in the recovery period. The present results indicate that sympathetic nervous response to cold is significantly enhanced in VWF patients. The exaggerated sympathetic response to cold in these patients is considered to contribute to the enhanced vasoconstriction of their extremities.
Dental technicians are exposed to various dusts in working laboratories. This study was conducted to measure level of silica in the respirable dust generated from dental fixed prosthodontics manufacturing processes using Fourier Transform Infrared Spectroscopy (FTIR), and to compare their occurrence of respiratory symptoms with that of non-dental hospital workers (control group). Respirable dusts were personally sampled from dental technicians working at dental laboratories in Seoul Korea according to NIOSH Method 0600. Fifty personal samples were obtained during porcelain or polishing process and weighed by a gravimetric method. Concentration of respirable dust was 651 ± 548 μg/m3 (Mean ± SD) with highest concentration of 2874 μg/m3 during the porcelain process and 725 ± 414 μg/m3 with highest concentration of 1764 μg/m3 during the polishing process. Concentration of silica was 6.51 ± 6.07 μg/m3 with 18.85 μg/m3 highest and 14.88 ± 11.21 μg/m3 with 50.98 μg/m3 highest for the porcelain and polishing process, respectively. Level of silica contents in the dust was 0.81% and 1.66% for the porcelain and polishing process, respectively. The level of silica contents and silica concentration were significantly different between the two processes. Comparing prevalence of respiratory symptoms between non-smoking seventeen dental technicians and thirty-five control workers, wheezing and rhinorrhea were significantly more manifested in the dental technicians than the controls. Total frequency of respiratory symptoms was also significantly higher in the dental technicians than the controls.
Related factors of low back pain (LBP) among school personnel were investigated. We designed a cross-sectional study employing questionnaires, which included a Japanese version of the Job Content Questionnaire. Subjects consisted of 3306 male and 3184 female school personnel in all public schools and kindergartens operated by Nagoya City, Japan. Prevalence of LBP in each work category was compared to that in general teachers of each gender after adjusting for age. Male teachers at schools for the handicapped and in classrooms for the handicapped showed significantly higher LBP prevalence. Among female participants, teachers at schools for the handicapped, physical education teachers, kindergarten personnel and school nurses displayed higher LBP prevalence. In work categories which demonstrated high LBP prevalence, low social support and low job satisfaction were related to LBP of school nurses despite low physical loads. High job demand and physical loads correlated to LBP in kindergarten personnel.
We assessed the association of white blood cell (WBC) count with different components of the metabolic syndrome (MS) in 5275 Japanese male office workers aged 23-59 years. There was a significantly crude correlation between WBC count and body mass index, systolic and diastolic blood pressures, total cholesterol, high-density lipoprotein cholesterol (negative), triglycerides, fasting plasma glucose, and uric acid (all P<0.001). After controlling for potential confounding factors, the adjusted means of WBC count were significantly higher in subjects with each feature of the MS (obesity, hypertension, hypercholesterolemia, low high-density lipoprotein cholesterol levels, hypertriglyceridemia, high fasting plasma glucose levels, and hyperuricemia) (all P<0.005). The adjusted WBC count increments in subjects with 1, 2, 3, 4, and ≥ 5 features of the MS were 0.28, 0.45, 0.68, 0.76, and 1.40 × 109 cells/l, respectively, compared with the subjects without features of the MS (P for trend<0.001). The adjusted means of WBC count increased significantly with the increasing number of features of the MS in both non-smokers and smokers (both P<0.001). These data indicate a strong association between WBC count and a number of disorders characterizing the MS independent of cigarette smoking among Japanese men.
Vanadium pentoxide is used as a catalyst and a ferrovanadium alloy ingredient in automotive steels and in jet engines and airframes. In addition, vanadium is found in fuel oils. Thus, occupational exposures to vanadium pentoxide and trioxide may occur during the cleaning of oil-fired ship boilers, and from oil-fired power station boilers. Occupational exposure to vanadium pentoxide induces green tongue, asthmatic symptoms and albuminuria with cast. Urinary citrate is freely filtered at the glomerulus, and its reabsorption in the proximal tubule is the major determinant of the rate of renal excretion. In this study, we exposed rat renal brush border membrane vesicles (BBMV) to vanadium pentoxide and examined their citrate uptake characteristics. The preincubation of BBMV with 1 mM V2O5 for 8 hours significantly inhibited citrate uptake compared with that of BBMV without V2O5 preincubation. These findings indicate that the preincubation of BBMV with vanadium pentoxide results in a time-dependent inhibition of citrate uptake by BBMV. These findings might contribute to nephrotoxicity in vanadium exposure.
We conducted 24-hour Holter electrocardiography (ECG) among shift workers to assess whether there were differences in the prevalence of ventricular and supraventricular premature beats between hypertensive (HT) and normotensive (NT) workers. Among the selected 24 male shift workers, 20 were fitted with 24-hour Holter ECG monitors. Nine workers were in the HT group and 11 the NT group. The prevalence of isolated supraventricular premature beats (SVPBs) and SVPB runs were higher in the HT group than in the NT group, but without statistical significance. The prevalence of ventricular premature beats (VPBs) was similar between groups. One worker in each group experienced ≥720 VPBs per 24 hours, while the worker in the HT group was detected as having a short run of VPBs. The results suggested the necessity of a larger scale study to clarify an association between hypertension and arrhythmias using 24-hour Holter electrocardiography.
During the periodic physical checkups in 1997-2000, the authors have found eleven cases of nasal septum perforation among 2, 869 welders in Ulsan, Korea. They have not suffered from diseases and conditions that could cause septum perforation such as tuberculosis, syphilis, and longterm use of topical corticosteroids. And also they did not have trauma history and surgical experiences on their nasal septum. To investigate the cause of septum perforation we reviewed the past history of pre-employment, the results of annual working environment survey and the material safety data sheets of welding rods and steels with which they have dealt. We also analyzed the concentration of several metals of welding fume and the concentration of blood and urinary chromium. In the result, we assumed that the nasal septum perforation of welders was due to chronic exposure to low-level hexavalent chromium.
In a household appliance plant, several rinse-free lubricating fluids have been used instead of neat mineral oils since 1994: mixtures of isoparaffinic hydrocarbons with 9 to 14 carbons per molecule. As such they denature keratin, irritate and defat the skin, and remove water from it. Work gloves have been worn over plastic gloves and separate, reusable, cotton inner gloves have been added to absorb sweat since skin problems were first recognized in 1994. All 74 males (mean ± SD, 38.8 ± 8.0 years) who work with the fluids were interviewed and given cutaneous examinations when indicated. While 4 cases of severe dermatitis and 31 cases of mild dermatitis were identified, 28 individuals gave a history of similar problems since the use of lubricating fluids. Their symptoms were typical of primary skin irritation. The hands were the commonly affected region (63 of 63 cases: 100%), followed by the thighs (15.9%) and trunk (11.1%). The work-related skin symptoms identified were less common in workers who immediately removed the liquid with soap and water, when it is spilled on the hands, than in those who did not, but the difference was not statistically significant (7/23 (30.4%) vs. 28/51 (54.9%), p=0.051 by chi-square test). Since skin contact with metalworking fluids (MWF) is often unavoidable, good personal hygiene is important in minimizing potential adverse health effects. Health education thus remains the most important preventive measure against irritant contact dermatitis among workers handling MWFs.