To clarify measures for making clearer instructions on how to read the results of general health checkups in a workplace by surveying the views of workers on these instructions, an anonymous self-administered questionnaire survey was conducted at a Japanese manufacturing plant. The responses of 984 male workers were analyzed. The average age of the subjects was 32.1 yr (range, 19-60 yr). Regarding the instructions, 4.1% of the subjects answered "definitely sufficient," 58.9% "somewhat sufficient," 28.0% "neither sufficient nor insufficient," 8.1% "somewhat insufficient" and 0.8% "definitely insufficient." Multiple regression analysis showed that the degree of examinees' satisfaction significantly correlated with the health condition (standard partial regression coefficient =0.189, p<0.001), knowledge of health management (standard partial regression coefficient =0.095, p=0.014), and fear of lifestyle-related diseases (standard partial regression coefficient =0.095, p=0.009). The adjusted R square value of the multiple regression analysis was 0.064. It is necessary to provide more detailed information to those with poor health. Because the instructions contain many difficult medical terms, health professionals must give instructions that are easy to understand. Those feeling fear of lifestyle-related diseases may already know how to read checkup results. It is necessary to promote awareness of lifestyle-related diseases targeting people unfamiliar with such diseases.
Many workers are exposed to vibration in their industrial environment. Vibration can be transmitted through a vehicle seat or a hand-held power tool. Excessive vibration exposure may cause health problems and therefore it is important that the worker's vibration exposure is assessed, which may require measurement by the equipment manufacturer or the employer. Human exposure to vibration may be measured using accelerometers; however, weighting filters are required to correlate the physical vibration measurements to the human's response to vibration. ISO 2631, BS 6841 and ISO 5349-1 describe suitable weighting filters, but do not explain how to implement them for digitally recorded acceleration data. ISO 8041 Annex C suggests a method but does not provide a solution. By using the bilinear transform, it is possible to transform the analogue equations given in the standards into digital filters. This paper describes the implementation of the weighting filters as digital IIR (Infinite Impulse Response) filters and provides all the necessary formulae to directly calculate the filter coefficients for any sampling frequency. Thus, the filters in the standards can be implemented in any numerical software.
Sleepiness is a major risk factor for serious injury and death in accidents. Although it is important to develop countermeasures to sleepiness to reduce risks, it is equally important to determine the most effective timing for these countermeasures. To determine optimum timing for necessary countermeasures, we must be able to predict performance errors. This study examined the predictability of subjective and physiological indicators of sleepiness during a vigilance task. Thirteen healthy male volunteers (mean age, 26.9 yr; SD = 5.98 yr; range 22-43 yr) participated in the study. Participants used the Karolinska sleepiness scale (KSS) to rate their subjective sleepiness every 4 min during a 40-min Mackworth clock test. Electrophysiological and performance data were divided into 10 epochs (i.e., 1 epoch lasted for 4 min). To estimate predictability, the data from the sleepiness indicators used for the correlation analysis were preceded by one epoch to the performance data. Results showed that sleepiness indicators (KSS score and electroencephalographic [EEG] alpha activity) and standard deviation of heart rate (SDNN) were significantly correlated with succeeding performance on the vigilance test. These findings suggest that the KSS score, EEG alpha activity, and SDNN could be used to predict performance errors.
This study was performed in a climatic chamber to evaluate the combined effects of noise intensity, heat stress, workload, and exposure duration on both noise-induced temporary threshold shift (TTS) and the recovery time by adopting Taguch's method. Fourteen subjects without previous significant noise exposure and smoking history were recruited to participate in this study. All hearing threshold levels at eight different frequencies (250 to 8,000 Hz) of better ear were measured in an audiometric booth by using the ascending method in 2 dB steps before each exposure condition. The test was also carried out after exposure to evaluate TTS at various times. The TTS recovery time was assessed using an audiometric test on all subjects at post-exposure times of 2, 20, 40, 60, 80 and 120 min, respectively. It was found that TTS depended mainly on the exposed noise dose and was enhanced by workload and heat stress. The TTS recovery time is dependent upon the magnitude of the initial hearing loss. In conclusion, TTS driven by noise exposure is enhanced by heat and workload. Further studies are required to evaluate the effects of workload with extreme temperature in a workplace environment.
In this study, we evaluated the effects of leaning posture on the kitchen counter, which was observed during dishwashing in a kitchen, on subjective discomfort and muscle activity in the low back and legs. Twelve female volunteers were asked to wash plates for 30 min in each of three working postures: (a) without support (No support), (b) supported by the kitchen counter (Counter), and (c) supported by a standing aid which was a stand equipment to support the shins and the counter (Aid and counter). In the "Aid and counter" posture, the angle of the bent trunk and the muscle activity in the low back were less than that in the "Counter" posture, which was less than that in the "No support" posture. Also, the muscle activities in the legs were greater in the "Counter" and "No support" postures than in the "Aid and counter" posture. We concluded that the effects of leaning posture on the kitchen counter were not enough to decrease the workload on the low back and legs. To improve the comfort of the dishwashing task, new measures, such as the standing aid, are needed.
In order to investigate the effects of Zn on Pb toxicities. Proportion of abnormal sperm, percentage of micronucleated polychromatic erythrocyte (MPCE), serum thyroid hormones (T3, T4) and cortisol were measured. Rats received intraperitoneal injection of 25 mg/kg Pb acetate, 4 mg/kg Zn acetate, both Pb acetate and Zn acetate, or normal saline as controls, once every two days, 7 times in total. No significant differences in whole blood Pb were detected between groups received Pb alone or both Pb and Zn. On the contrary, the concentration of whole blood Zn in the group given Zn alone was significantly higher than that in the group that received both Pb and Zn. In the groups given Pb alone or both Pb and Zn, proportion of abnormal sperm, frequency of MPCE and serum cortisol were significantly higher than those in controls, whereas serum T3 and T4 were significantly lower than in controls. In the group given both Pb and Zn, T4 was decreased most obviously among the four groups. While the proportion of abnormal sperm was less in the group given both Pb and Zn than in the group given Pb alone. These findings suggest that Zn coadministration might alleviate toxic effects of Pb on the male reproductive system, whereas it could enhance the toxicity on thyroid function. Zn did not affect the toxicities of Pb on cytogenetic systems as indicated by MPCE percentage, and on serum cortisol levels under the dose of the present study. Our results suggested the double-edged effects of Zn on Pb toxicities in different organs. Therefore, the effects of Zn on Pb toxicities should be evaluated systematically.
The study examined how nap length, nap timing and sleep quality affect early morning performance (6:00 to 8:00). Twelve students participated in a simulated nightshift schedule (22:00 to 8:00) where the length and timing of nocturnal naps were manipulated (0:00-1:00, 0:00-2:00, 4:00-5:00 and 4:00-6:00). A performance test battery was administered consisting of a psychomotor vigilance test, a logical reasoning test, and a visual analogue scale for subjective fatigue and sleepiness. The results showed that a 120-min nap sustained early morning performance better than a 60-min nap. Taking a nap earlier or later did not affect the neurobehavioral performance tests, although participants slept more efficiently during naps later in the night shift. A negative effect of a nocturnal nap during the night shift on subsequent daytime and nocturnal sleep was not observed in the sleep architecture. It still remains unclear whether slow wave sleep plays an important role in sustaining early morning performance. In terms of work safety and sleep health, the results suggest that a longer and later nap is beneficial during night shifts.
This study was initiated to investigate the effects of health counseling under Total Health Promotion Plan (THP). The study populations consisted of 1,655 working men who had an initial THP-based counseling and a follow-up 3 yr later (the THP group; the counseling was given on a once-three year basis), and 1,655 age- and body mass index (BMI)-matched controls (working men who had no health counseling; the control group). In the THP group, systolic blood pressure (SBP) and the prevalence of excessive alcohol drinking were decreased, and nutritional score was improved, although BMI was increased. In contrast, SBP, BMI and the ratio of excessive drinkers were all increased in the controls. Multiple regression analysis of the THP group showed that the reduction in SBP was positively associated with the increase in maximal oxygen consumption (VO2max) and physical activity scores, as well as the decrease in BMI. In sub-group analyses of the THP group, VO2max and physical activity scores were increased, and BMI did not change in the sub-group with marked BP decrease. In the sub-group with marked BP increase, however, BMI was increased, and VO2max was decreased. The ratio of excessive drinkers was reduced only in the sub-group with marked BP decrease. The obese-hypertensive subjects in the THP group showed decreases in BMI and BP, and increases in VO2max. Thus, these results appeared to suggest that health counseling given even at a low frequency of once in three years prevented the age-associated increase in BP through improvement of physical endurance, decrease in alcohol intake and reduction in body weight.
Ethylene glycol monoethyl ether (EGEE) can cause damage to testes and sperm, and its metabolites are believed to play an important role in its toxicity. Aldehyde dehydrogenase 2 (ALDH2) is involved in the metabolism of this chemical. To investigate whether and how the enzyme affects the toxicity of EGEE, we conducted experiments comparing Aldh2 knockout mice with wild-type mice. Administration of EGEE at 100 and 600 mg/kg/day for one week did not induce any significant change in the weight and body weight ratios of testes, prostate and epididymides in either Aldh2 knockout or wild-type mice. However, motion of sperm from the spermaduct, as analyzed with a Hamilton-Thorne Sperm analyzer, was slightly decreased in the low dose group, and significantly lower in the high dose group; and the percentage of progressive sperm was also reduced in the two EGEE groups. This effect of EGEE treatment was observed in the wild-type, but not in the Aldh2 knockout mice. Sperm motion from the cauda epididymides was not affected. On the other hand, the concentration of ethoxyacetic acid, a metabolite of EGEE, in 24 h pooled urine of EGEE-treated Aldh2 knockout mice was not significantly lower than that of the wild-type mice on most days of urine sampling. These results suggest that inactivation of the ALDH2 enzyme due to gene mutation may be linked to differences in the susceptibility to EGEE-induced sperm toxicity.
A study was conducted with staff at a fly-in/fly-out mine camp to determine the: hydration knowledge, perceptions and behaviours; hydration status and needs; and perceived taste of potable water. A structured questionnaire was used to survey the self-reported hydration behaviour, knowledge and perception of. The study of the hydration status and needs of day shift staff while at the residential camp comprised measurements at 1800 h and 0600 h of weight, urine specific gravity and fluid intake. Staff rated the perceived taste of bottled, filtered potable and unfiltered potable waters on a seven point visual analogue scale. The mean correct responses to the knowledge items surveyed (n=78) was 9.2 out of 12. Three-quarters (n=15) of the 20 responses to an open-ended question suggested improved water taste to increase water consumption. In the hydration status study (n=46), the mean urine specific gravities at 1800 h and 0600 h were both 1.022, and the median fluid intake and loss rates were both 2.1 ml.kg-1.h-1. Staff (n=105) rated unfiltered water (median 4.0) as tasting significantly worse than bottled (median 6.0) or filtered (median 6.0) waters (Friedman test, p<0.001). While dehydration knowledge appears adequate, the observed fluid intakes and specific gravities demonstrate that external factors such as perceived taste of water influence hydration behaviour.
This study aims to evaluate blood lead level (PbB) and blood pressure of bus drivers in Bangkok, Thailand, after the phasing out of lead in gasoline. The subjects comprised of 439 male bus drivers whose age ranged between 23 and 59 yr with the mean age of 42 ± 8 yr. Average working experience was 10 ± 7 yr. The mean of the systolic and diastolic blood pressure were 131 ± 17 and 81 ± 11 mmHg, respectively. PbB ranged from 2.5 to 16.2 μg/dl with the mean PbB of 6.3 μg/dl. Prevalence rate of systolic and diastolic hypertension among bus drivers were 23.0% and 18.2%, respectively. There were significant correlations between PbB and blood pressure both in systolic and diastolic blood pressure after controlling for age, BMI, alcohol consumption, smoking and physical exercise. However, the data on psycho-social factors which may affect on blood pressure of bus drivers were not available. Therefore, further study is needed to clarify the relationship between blood pressure and psycho-social stress among bus drivers in Bangkok. These findings suggested lead exposure at low PbB is related to increases in blood pressure.