Abiko H.,Japanese National Institute for Occupational Safety and Health
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2017
Silica gel is commonly used as a sampling agent in small glass tube products for work environment measurements of organic solvent vapor, as established by the Industrial Safety and Health Act in Japan. However, to date there has been no national standard for sampling tube products, and the extraction efficiency of adsorbed organic solvent vapor from silica gel significantly affects the accuracy of measurement. Here, we have investigated the material properties of silica gel used in typical Japanese sampling tube products, and the effects on the efficiency as determined by the phase equilibrium method. This study focused particularly on specific surface area, porosity and grain diameter of silica gel specimens. © 2017 The Ceramic Society of Japan. All rights reserved.
Shibata N.,Japanese National Institute for Occupational Safety and Health
International Journal of Industrial Ergonomics | Year: 2015
The aims of this study were to propose multiply scale factors for evaluation of discomfort of standing persons and to investigate whether there exist differences between multiplying factors used for evaluation of discomfort of standing persons and those of seated persons exposed to WBV. Twelve male subjects were exposed to twenty-seven stimuli that comprise three acceleration magnitudes (0.2, 0.4, and 0.8 m/s2 r.m.s.) along fore-aft (x), lateral (y) or vertical (z) direction. The subjects with seated or standing posture on the platform of the vibration test rig rated the subjective discomfort for each stimulus that has frequency contents ranging from 1.0 Hz to 20 Hz with a constant power spectrum density. The order of presentation of the test stimuli was fully randomized and each stimulus was repeated three times. The subjective scale for discomfort was calculated by using the category judgment method. The best combinations of multiplying factors were determined by calculating correlation coefficients of regression curves in-between subjective ratings and vibration magnitudes. In all the directions, body posture significantly influenced on subjective discomfort scales. Particularly in the fore-aft and lateral direction, the upper limit of all the categories for the standing posture resulted in higher vibration acceleration magnitudes than those for the seated posture. In contrast, in the vertical direction, only the upper limit of category "1: Not uncomfortable" for standing posture was observed to be higher than that for seated posture. The best agreement for ISO-weighted vibration acceleration occurred at x factor of 1.8 and y factor of 1.8 in the standing posture and x factor of 2.8 and y factor of 1.8 in the seated posture. The results suggest that seated people respond more sensitively and severely in perception of discomfort to fore-aft and lateral vibration than standing people do while standing people respond more sensitively and severely to vertical vibration than seated people do. Thus the effects of body postures on multiplying factors should be considered in evaluation of discomfort caused by whole-body vibration. Relevance to industry: This study reports differences in subjective response of standing persons to fore-aft, lateral and vertical whole-body vibration. The results obtained in this study propose the fundamental data on the sensitivity to whole-body vibration exposed with standing posture. © 2015 Elsevier B.V..
Tomita H.,Japanese National Institute for Occupational Safety and Health
IEEJ Transactions on Fundamentals and Materials | Year: 2012
In this study, I experimentally clarified the nature of the characteristics of the electrostatic discharge (ESD) that occurs when a charged object moves toward a stationary grounded object. The spark lengths, discharge currents, and induced voltages in a magnetic probe were measured when a charged metallic spherical electrode connected to a 422 pF capacitor approached a stationary grounded object, which was the current target, for different moving speeds of the charged metallic spherical electrode in the range of 1-100 mm/s. The charge voltages of the capacitor were +6.5 kV and +10 kV. According to the result, the average gap length shortened with the moving speed of the spherical electrode. The average peak values of the discharge current and the induced voltage were likely to increase with the moving speed of the spherical electrode. The average rise times of the discharge current and the induced voltage were likely to reduce with the moving speed of the spherical electrode. The relation between the spark length and the discharge current due to ESD can be explained qualitatively by using an equation derived from the spark resistance formula proposed by Rompe and Weizel. © 2012 The Institute of Electrical Engineers of Japan.
Kubo T.,Japanese National Institute for Occupational Safety and Health
Sangyō eiseigaku zasshi = Journal of occupational health | Year: 2013
The period of leisure is an appropriate time to recover from work-induced fatigue, though some recovery takes place during rest breaks at work. Recently, much attention has been paid to the critical role of leisure activity in recovery. However, the findings relevant to shiftwork nurses who cannot take a day-off regularly are limited. This study explored how leisure activity during days off and shift work schedule are associated with recovery from fatigue in nurses working rotating shifts. A total of 426 nurses working rotating shifts at a university hospital returned a questionnaire regarding leisure activity and fatigue (response rate: 81.5%). Nurses were eligible for this study if they were female, worked 2 or 3 shifts, and had no missing data. A total of 390 respondents satisfied the inclusion criteria. A factor analysis classified their responses on how to spend an assumed period of two consecutive days off into three activity types: outdoor-, sleep-, and indoor-oriented. Fatigue (recovery from fatigue, accumulated fatigue, burnout), work conditions (working time, overtime, nightshift napping), sleep (sleep duration before day shift or day off, sleepiness) were measured. These data were analyzed using a two-way mixed model analysis of covariance (type [outdoor, sleep, indoor], shift schedule [two or three-shift system]). Covariates included age, length of career, partner, children, and hospital ward. Multiple regression analyses were performed to examine the factors determining the level of fatigue. Outdoor-oriented nurses showed significantly faster fatigue recovery, lower accumulated fatigue and less burnout symptoms than others, regardless of the shiftwork schedule. In contrast, sleep-oriented nurses showed significantly slower recovery from fatigue. Besides, their level of fatigue deteriorated more when they worked under a 3-shift system (counter-clockwise) compared with under 2-shift system (with mainly 16-hour nightshift). Multiple regression analysis indicated that sleep-oriented type of leisure activity, workload perception of working time, work-induced insomnia and length of nightshift naps were significantly related to fatigue-related outcomes. The primary finding of this study suggests that the level of fatigue is associated with the type of leisure activity, especially sleep-oriented activity, during shiftwork nurses' days off. Also, ensuring sufficient nightshift nap time may be one of the most important nightshift-related factors for recovery from fatigue. The present findings may have implications for appropriate activities during days off as factors facilitating recovery from work, though further investigations are needed to examine the causal links.
Takaya M.,Japanese National Institute for Occupational Safety and Health
Sangyō eiseigaku zasshi = Journal of occupational health | Year: 2010
In order to assess the exposure risks of multiwall carbon nanotubes (MWCNT) for packing workers, we carried out real-time monitoring in the two types of packing facilities of MWCNT, and exposure measurements for the packing workers. In the real-time monitoring, a scanning mobility particle sizer (SMPS) and an optical particle counter (OPC) were used to measure nanoscale particles and sub-micron/micron scale particles, respectively. A personal sampler with PM 4.0 was used to measure the personal exposures in the packing facilities. One of the packing facilities is manually operated and the other is automated. The concentrations of airborne dust in both facilities were almost the same as each other at 0.24 mg/m(3) (total dust). However, the results of personal exposure measurements were quite different between the two facilities. The exposure concentrations of workers in the manually and automated operations were 2.39/0.39 (total/respirable) mg/m(3) and 0.29/0.08 (total/respirable) mg/m(3), respectively. From the time series study, submicron scale particles were released into the workplace air when the CNT products were put into temporary container bags from a hopper and manually packed into shipping bags. However, the task-related nanoscale particle release was not observed. The manual packing operation is one of the "hot spots" in MWCNT production facilities, and automation brings much improvement to reduce MWCNT exposure.
Ohsawa A.,Japanese National Institute for Occupational Safety and Health
Journal of Electrostatics | Year: 2013
This paper reports results from a computational investigation of charge neutralisation with DC, AC, and pulse-DC corona ionisers using 2-D axisymmetric electrohydrodynamic modelling with an emphasis on minimising the offset voltage. The results showed that balanced DC ionisers can effectively neutralise the charge of a conductive plate; however, balanced AC and pulse-DC ionisers give rise to a certain offset voltage with an oscillation caused by alternate mono-polar space charges created near the ionisers resulting from ions emitted from the ionisers. In addition, we suggest a modification for AC and pulse-DC ionisers to minimise the offset voltage, including its AC component. Consequently, we found that continuously balanced ions emitted from ionisers which can create a quasi-neutralised charge distribution by positive and negative ions in the entire space at a steady state are of significant importance to make the offset voltage zero. © 2012 Elsevier B.V.
Takahashi M.,Japanese National Institute for Occupational Safety and Health
Journal of Physiological Anthropology | Year: 2012
Good sleep is advantageous to the quality of life. Sleep-related benefits are particularly helpful for the working class, since poor or inadequate amounts of sleep degrade work productivity and overall health. This review paper explores the essential role of sleep in healthy work schedules and primarily focuses on the timing of sleep in relation to the work period (that is, before, during and after work). Data from laboratory, field and modeling studies indicate that consistent amounts of sleep prior to work are fundamental to improved performance and alertness in the workplace. In addition, planned naps taken during work maintain appropriate levels of waking function for both daytime and night-time work. Clearly, sufficient sleep after work is vital in promoting recovery from fatigue. Recent data also suggest that the time interval between shifts should be adjusted according to the biological timing of sleep. Although sleep is more likely to be replaced by job and other activities in the real life, research shows that it is worthwhile to revise the work schedules in order to optimize sleep before, sometime during and after the work period. Therefore, we suggest establishing work-sleep balance, similar to work-life balance, as a principle for designing and improving work schedules. © 2012 Takahashi.
Shimada Y.,Japanese National Institute for Occupational Safety and Health
Journal of Chemical Engineering of Japan | Year: 2012
The safety of a chemical process plant can be achieved through plant-lifecycle engineering (Plant-LCE), which is performed from research and development to plant safety design, construction, and manufacturing (production and maintenance) stages, as well as at each engineering stage. To expressly provide a framework that can perform coherent decision making through the plant-lifecycle and at each stage, it is effective to develop a business process model that systematizes the activities related to engineering, production, etc. and represents the ideal and consistent business flow for each company. The safety division of the Society of Chemical Engineers Japan (SCEJ) has advanced the development of a business process model of Plant-LCE which consists of the business process models for process safety design, production management, plant maintenance, and process safety management (PSM). The original business flow for each company can be developed by referring to these business process models as reference models. This business flow can clarify what kind of activities should be performed at each stage, what kind of information on an activity should be collected, how it should be conveyed to other engineering activities, etc. In this paper, we review the challenges in developing business process models to realize a PSM environment logically. © 2012 The Society of Chemical Engineers, Japan.
Takahashi M.,Japanese National Institute for Occupational Safety and Health
Sleep and Biological Rhythms | Year: 2014
Shift work poses a significant threat to multiple aspects of working life. The present review addresses the health, safety/performance, and psychosocial issues associated with shift work. Recent studies have revealed that health disorders due to working in shifts are closely related to dysfunction of sleep and the circadian timing system. Safety and performance problems such as occupational injuries and poor work performance that occur during abnormal working hours can be explained by impaired neurobehavioral function. An increased level of understanding regarding shift work problems as well as sleep and circadian biology should be translated into evidence-based strategies to assist shift workers. Although some promising countermeasures including sleep and circadian approaches have been proposed, many questions regarding better shift schedules and fatigue risk management remain unsolved. In particular, shift work has been defined differently in previous studies, leading to confusion and errors when estimating the associations between shift work and outcomes. Additionally, there are no validated, reliable indicators to represent the adaptability of shift work. Such indicators, if available, could be used for health evaluations of current shift workers and the early detection and treatment of poor adaptation to a given shift schedule. Clearly, modern society exists with individuals who work in shifts. Therefore, effective countermeasures must be developed to reduce the risks arising from shift work. Sleep and circadian biology are expected to direct these processes. © 2014 Japanese Society of Sleep Research.
Miura N.,Japanese National Institute for Occupational Safety and Health
The Journal of toxicological sciences | Year: 2013
Biological defense factors show diurnal variations in their expression levels or activities. These variations can induce the different sensitivity to external toxicants of a day. We reported earlier that mice showed clear diurnal variation of cadmium (Cd)-induced toxicity, i.e., chronotoxicity. In this report, we investigated additional new evidences for the cadmium (Cd)-induced chronotoxicity, and considered the mechanisms contributed to this chronotoxicity. Male C57BL/6J mice were injected with CdCl2 (6.4 mg/kg, one shot) intraperitoneally at 6 different time points of a day (zeitgeber time (ZT); ZT2, ZT6, ZT10, ZT14, ZT18 or ZT22) followed by monitoring the mortality until 14 days after the injection. We observed extreme difference in survival numbers: surprisingly, all mice died at ZT2 injection while all mice survived at ZT18 injection. Moreover, in non-lethal dose of Cd (4.5 mg/kg), the values of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) used as indexes of hepatotoxicity markedly increased at ZT6 injection while mostly unchanged at ZT18 injection. To consider the mechanisms of this extreme diurnal variation, we examined biochemical studies and concluded that the diurnal variation was not caused by the differences in hepatic Cd level, basal hepatic metallothionein (MT) level, and induction level or induction speed of hepatic MT. We suggested that one of the candidate determination factors was glutathione. We believe that the "chronotoxicology" for metal toxicity may be classic, yet new viewpoint in modern toxicology field.