Validation of foot plantar pressure sensor data used to estimate standing, sitting, and moving durations in one working day.

BACKGROUND: Maintaining immovable postures for long durations might be a cause of low back pain. However, the relation between low back pain and the maintenance of postures for long durations has been unclear. Therefore, the durations of several postures in one working day should be measured to evaluate the risk of low back pain, although the available measuring methods are limited. To the best of our knowledge, no study has reported the development and investigation of a foot plantar pressure sensor for measurement of standing, sitting, and moving durations in daily work routines. Thus, in this study, we aimed to develop a foot plantar pressure sensor that could withstand long-term loads in the workplace. Furthermore, we aimed to evaluate the estimated results of standing, sitting, and moving durations among factory workers using the developed foot plantar pressure sensor. METHODS: The developed foot plantar pressure sensor obtained a percentage difference within ±5% to estimate standing, sitting, and moving durations in the laboratory. We measured foot plantar pressures of 20 factory workers to estimate standing, sitting, and moving activity in one working day using data obtained by the foot plantar pressure sensor. The estimated standing, sitting, and moving durations were compared with the human estimation of photo data obtained by a wearable camera. RESULTS: The agreement rate (Cohen's kappa coefficient) was 0.75 between the evaluation using the foot plantar pressure sensor data and human estimation using a wearable camera. Cohen's kappa coefficient was 0.81 in subjects who sat for ≥30% during daily work and 0.68 in subjects who sat for <30%. CONCLUSION: Our foot plantar pressure sensor effectively measured the standing, sitting, and moving durations in daily work that requires various movements and assumption of postures.

[Design and Evaluation of Miniature Cyclones for Dust Indicators].

Dust indicators based on light scattering photometers are widely used to measure aerosol concentrations in work environments. These concentrations at workplaces in Japan are measured by these dust indicators and calibrated by mass concentration in order to control workers' exposure to dust. The mass concentration in a specific point in a workplace is measured simultaneously with a dust indicator. The mass concentration of the respirable fraction of dust particles should be determined by the gravimetric method with low volume air samplers or other devices, but some dust indicators are not equipped with a size separator for respirable fraction, and we used to get unstable results at the calibration. In this study, we designed miniature cyclones for a dust indicator and evaluated their performances of respirable fraction and PM2.5 fraction.

Assessment of exposure to voices and noise via earphones in manufacturing industry workers in Japan.

OBJECTIVES: There is concern that sound via earphones and headphones attached to headsets used in workplaces may be a risk factor for noise-induced hearing loss (NIHL). Although there are some previous studies investigating exposure to noise from headphones, almost none have assessed the risks to workers who use earphones. We assessed exposure to noise among workers who regularly wear earphones in noisy workplaces. METHODS: The subjects of this study were 21 workers who regularly wear earphones in three manufacturing companies in Japan. The sound pressure output from earphones and personal exposure to occupational noise was measured for each worker. A noise-dosimeter was used to measure individual exposure to occupational noise. The sound pressure output from the earphones was measured by recording the electric signal with a data recorder attached to the earphones, and the recording was analyzed by playing it back in the laboratory through a sound analyzer via an ear simulator. RESULTS: The mean scores for personal exposure and earphone output LAeq were 87.9 dB and 87.6 dB, respectively. Earphone output LAeq exceeded 85 dB for two-thirds of the subjects. Nearly all the subjects lacked hearing protection devices (HPDs) on their earphones. CONCLUSIONS: The results suggest that workers who use earphones in noisy workplaces are exposed to the following NIHL risk factors: (1) they are deprived of the opportunity to fit appropriate HPDs, and (2) the sound pressure output from the earphones themselves exceeds the occupational exposure limit.

Temporary threshold shifts at 1500 and 2000 Hz induced by loud voice signals communicated through earphones in the pinball industry.

To assess the risk of hearing loss among workers using earphones as communication devices at noisy worksites, we compared temporary threshold shifts (TTS) between ears on which workers wore earphones and ears on which no earphones were worn. We measured ambient noise and personal noise exposure as well as noise generated by and passed through earphones by applying frequency analysis at three pinball facilities during their hours of actual operation. We assessed hearing levels before and after a work shift (prework and postwork) of 54 workers by pure tone audiometry at six frequencies. The time-weighted averages for ambient noise and personal noise exposure exceeded 85 dB(A) and 90 dB(A), respectively. Overall sound pressure levels generated by and passing through earphones reached 109 dB(A). The one-third octave band spectrum of the earphone noise during the shift exceeded 90 dB(SPL) in the range of 315-2000 Hz. The number of ears demonstrating a TTS, defined as a shift of 10 dB or more in postwork over prework hearing thresholds, was significantly greater at 1500 and 2000 Hz among ears with earphones (P < 0.05 and P < 0.01, respectively) compared to those without. The reverse was observed at 4000 Hz for ears without earphones (P < 0.01). Workers wearing earphones or headsets as communication devices in noisy environments are exposed to high risk of hearing loss, particularly at the frequencies of 1500 and 2000 Hz. Ideally, hearing conservation programs for such workers should account for potential hearing losses at frequencies of 2000 Hz or lower frequencies induced by amplified voice signals.

Technique for continuously monitoring core body temperatures to prevent heat stress disorders in workers engaged in physical labor.

OBJECTIVES: Measuring core body temperature is crucial for preventing heat stress disorders in workers. We developed a method for measuring auditory canal temperatures based on a thermocouple inserted into a sponge-type earplug. We verified that the tip of this thermocouple is positioned safely, allowing the wearer to engage in normal physical tasks; this position averaged 6.6 mm from the tympanic membrane. METHODS: To assess this technique, we had six healthy male students repeat three cycles of exercise and rest (20 min of exercise and 15 min of rest) in a temperature-controlled chamber with temperatures set at 25, 30, or 35 degrees C, while monitoring the auditory canal, esophageal, rectal, and skin temperatures. RESULTS: We observed differences of a mere 0.30-0.45 degrees C between rectal temperatures and auditory canal temperatures measured with the thermocouple, the smallest such difference reported to date in studies involving auditory canal temperature measurement. CONCLUSIONS: We conclude that monitoring temperatures based on a technique involving an auditory canal plug can be used to estimate rectal temperatures accurately, and thereby to avoid conditions leading to heat stress disorders.

Effectiveness of a head wash cooling protocol using non-refrigerated water in reducing heat stress.

Envisioning a cooling method and aiming at maximum feasibility and simplicity, we designed an experimental intervention-control study based on non-refrigerated water usage, consisting of pouring 2 l of 23.0 degrees C water simultaneously on head and hands for one minute, after every 20 min of exertion. The subjects were 11 fit male individuals between 19 and 26 yr old. Each individual participated in one control and one intervention measurement in a climatic chamber at 35 degrees C and 60% humidity (31.5 degrees C WBGT) on different days. Heart rate, rectal, esophageal, skin and external ear canal temperatures were monitored constantly. Each experiment consisted of 10 min of basal recording followed by 3 intervals of 20 min of cycling and 15 min of rest. Stabilometry and visual reaction time tests were performed before and after each resting period. A questionnaire evaluating equilibrium, concentration, alertness and tiredness was administered at the beginning and at the end of every experiment. Paired t-test analysis revealed significant improvements in subjective parameters (all p<0.05), as well as skin (p<0.05), external ear canal (p<0.01) and esophageal (p<0.05) temperatures during the rest periods. Repeated measurement analysis of variance revealed significant cooling in all the aforementioned temperatures except the esophageal temperature (p=0.28). Other parameters were not significantly different. Our findings indicate that this method has subjective and physiologic positive effects, and thus can be used as a complementary low cost method to cool subjects safely.

Heat exposure control using non-refrigerated water in Brazilian steel factory workers.

To test an economically reasonable method to reduce thermal stress, we performed an alternated intervention-control study on 2 groups of 8 male steel workers performing the same jobs, using 2 l of water at ambient temperature (23.5 degrees C +/- 1.4), poured on the head and hands. Each group participated for 2 d as control and 2 d as intervention during 4 consecutive summer days in Brazil, 5 h per shift per day. Testing was done by: 1) recording of temperature by thermistors placed on the external ear canal through earplug, skin (chest, upper arm, inner thigh, outer calf) and clothes; 2) recording of heart rate; and 3) Wet Bulb Globe Temperature recording. The intervention was held hourly, when body weight and water intake were evaluated. Symptoms and subjective sensations were evaluated in the beginning and at the end of each shift. No differences were observed in external ear canal and skin temperatures. Subjective thermal sensation (p = 0.018), sweat perception (p = 0.043), and tiredness (p = 0.028) presented positive statistically significant results when comparing intervention to control measurements. In conclusion, our results could not provide evidence that the proposed method cools the analyzed temperatures, although the subjective evaluation suggests a decrease in the head skin temperature, which could be a useful comfort measure.

[A systematic review of working hours and mental health burden].

There is growing concern over the possible increase in mental health problems among Japanese workers. This trend is generally regarded as a reflection of Japan's prolonged economic depression and changes in working environment. In fact, claims for compensation for industrial accidents related to mental health diseases have been rapidly increasing in recent years. Working hours, personal-relationships, support from supervisors/co-workers, job demand, job control, and payment are known to affect workers mental health. In 2004, the Government announced a guideline to combat overwork and mental health problems at work places. This guideline articulates that long overtime working is a major indicator, and workers who work over 100 h overtime in a month should be encouraged to see an occupational physician. This guideline takes into account the practicalities of occupational health at work places and the empiric knowledge that long working hours might associate with workers mental health status. It may be reasonable to assume that long working hours affect workers health status both psychologically and physiologically, interacting with a variety of occupational factors, particularly job stress. However, the association between working hours and workers mental health status has not been fully clarified. The present article aimed to provide a systematic review of the association between working hours and mental health problems. The authors conducted a systematic review of the published literature on the association between working hours and mental health problems using PubMed. Of 131 abstracts and citations reviewed, 17 studies met the predefined criteria. Ten of these are longitudinal studies, and the others are cross-sectional studies. Seven of the 17 studies report statistically significant associations between working hours and mental health problems, while the others report no association. In addition, comparison among these studies is difficult because a variety of measurements of working hours were used. The present review found inconsistent results in the association between working hours and mental health burden.

[Long working hours and cardiovascular diseases: a systematic review].

Three years have passed since the countermeasures against the adverse health effects of overwork started in Japan, and fruitful outcomes have been expected. In the current study, a systematic review of articles was performed regarding the association of long working hours (LWH) with cardiovascular diseases (CVD) to obtain recent evidence of their association. An electronic database search was conducted using PubMed among English-written original articles published until December, 2004. A total of twelve articles were found conforming to the study's inclusion criteria, but evidence supporting the association of LWH and CVD was not detected. However, some distinctive studies related to the prevention of CVD were found relating to the concept of sensitive psychosocial factors such as vital exhaustion, and to the statistical modeling of occupational factors and biological indicators with the interaction term of psychosocial factors. Further studies will be needed to clarify the association of LWH and CVD.

[Body cooling capacity of water circulated cooling pants during lower body exercise in a hot environment].

We investigated the body cooling capacity of water-circulated cooling pants during lower body exercise in a hot environment. Five subjects were asked to ride a bicycle ergometer and to keep a work rate of 75 W continuously for 20 minutes. They then rest on the ergometer for 15 minutes, in a climate chamber kept at WBGT = 31.5 degrees C. They repeated the same procedure three times under three different conditions; 1) wearing cooling pants with cold water supply; 2) wearing cooling pants without water supply; 3) wearing short pants instead of cooling pants. Esophageal temperature and heart rate of the subjects, when their cooling pants were supplied with cold water, were lower compared with the condition without water supply, and were almost the same as the condition wearing short pants. Water-circulated cooling pants should effectively cool the body at work where the worker has to wear pants that cover his legs to prevent injury.

[Development of a computerized sound attenuation measurement system of hearing protectors based on Japanese Industrial Standard(JIS)].

Sound attenuation measurement of hearing protectors is done in accordance with JIS T 8161 in Japan. In the JIS T 8161 it is stated that more than three non-coherent sets which include a noise generator, one-third octave band-pass filter, amplifier, calibrated attenuator and signal interrupter are required. To realize this measurement system, various expenses and a large space are required. In our study, four channel test signals were generated by our programs, and fed to a digital/analog converter. Consequently, the hardware of a noise generator and one-third octave band-pass filter could be reduced. Moreover, a program, which automatically controlled sound pressure level by digitally controlled attenuators, was developed with the result that the sound attenuation measurement could be performed by operating the mouse. Furthermore, sound attenuation of the earplug was measured in accordance with JIS T 8161 to evaluate our system. The result showed that practical sound attenuation values were obtained by easy operation. It was considered that this system was effective in hardware reduction, and useful for sound attenuation measurement of hearing protectors.

Effect of dilution of sports drink on water balance and beverage preference of heat-exposed steel workers.

Eight skilled workers engaged in heat-exposed work in front of a blast furnace in a steel factory were asked to drink a sports drink or one of its dilutions of x 2, x 3, or x 5 during a regular daytime shift in the summer of 1999. A regular lunch was taken and the examined beverage was iced and was allowed to be consumed ad libitum. The beverage was changed each day during four days of the experiment without informing the dilution ratio. The non-diluted beverage contained 21 mEq/l of Na+, 5 mEq/l of K+, 6.7 g/dl of carbohydrate. In average, the body temperature measured in the ear canal was elevated by 0.34 degree C, the loss of body weight was 1.77 kg, total beverage intake was 1,875 g, total amount of urine was 291 g, and the total water loss was 3,732 g (1,350-5,810 g) during a single shift. Twenty out of 24 cases experienced more than 1.5% of weight reduction during morning work without noticing any subjective symptoms of dehydration. The amount of weight loss during morning work was significantly smaller when x 2 or x 3 dilution was taken compared to a non-diluted beverage. The mean value of urinary Na+ concentration was decreased after 8 hours of work; however, the difference was not significant. The urinary K+ concentration was significantly increased. When the total amount of urinary sodium excretion in stored urine was calculated, the x 3 dilution recorded the largest amount. Regarding palatability, the x 2 dilution received the best evaluation, whereas all subjects felt the original beverage as too condensed. We did not observe any adverse effect from diluting the sports drink for x 2 or x 3, when supplying them as water and electrolyte replacements for dehydrated steel workers.

[Actual situation of medical checkups carried out by Industrial Health Organizations in Japan--manpower and service].

Japanese Industrial Health Organizations (IHOs) have been taking part in medical checkups for employees in accordance with the law of industrial safety and health in Japan. We carried out a questionnaire survey for each IHO in order to learn the actual number of full-time doctors and their proportion of work time. We sent a questionnaire to 112 IHOs (members of International Federation of Industrial Health Organizations) by mail, of which 77 replied (68.8%). In addition, we carried out an interview survey in 3 IHOs. The actual number of full-time doctors was 0 to 51, about half of IHOs have less than 5 doctors/each. Regarding the proportion of work time, among full-time doctors, half of them take part in general health checkups. About 70% of nurses' work time is taken up doing health checkups. The results revealed that the number and the proportion of work time of full-time doctors depends on the characteristics of the area and the background of the organization, for instance, what kind of hygiene services they provide. Depending on the doctors' work style (e.g. full-time or part-time) and their specialities and experience, their work may be shared. Japanese employers are required to report the number of workers with abnormal findings found by medical checkups to the Labor Standards Office. Many IHOs provide service to employers in filling out their reports. Thus, we also asked each IHO about this service. Forty out of the 77 IHOs (51.9%) answered that they are providing statistical analysis and the filling-out service. They count the number of workers with abnormal findings in each company and helped the employer to fill out the report form. Twenty-nine of those 40 IHOs responded that they decided which findings were "abnormal" by using only items that are set by law. However, 7 IHOs reported the fact that they also add some optional items when making the decision. The prevalence of workers with abnormal findings in annual medical checkups, which is one of the msot important indices of the state of occupational health, should be measured by using an objective definition and by being compatible with future systems of medical checkups for all Japanese workers. Although IHOs are endeavoring to improve their level, it will be difficult, and because of diversities in the way of periodical medical checkups among IHOs, there are still many problems to be solved.

[Occupational physician's role regarding return to work of workers with acquired disability].

Occupational physicians are expected to play important roles in helping workers with an acquired disability return to work. However, the key elements to develop a successful program to help these workers return to work are still unclear. In this study, we searched the literature referring to occupational physicians' role in the return-to-work process of the workers with acquired disability. Many of these studies mentioned the following; occupational physicians should start co-operating with the treating physician right after the appearance of the disability and exchange medical and occupational health information with each other. When a disabled worker wishes to return to work, the occupational physician in charge should carefully evaluate his/her work ability, and fitness for the work. We also performed a hearing survey at 15 diverse institutions and organizations that are generally aimed at promoting employment, social welfare and medical service for disabled persons located in at least a 5 million population prefecture in Japan. Among them, the Local Occupational Center for the Disabled functions as the practical gateway for employment, and the Health and Welfare Center is the principal window for the social welfare of the disabled. However, their services are sometimes limited to only those who have become jobless and not for those returning to their original work. We considered that occupational physicians should also communicate positively with the organizations to promote successful returning of the workers with acquired disability to their former work.

[Occupational safety and health at small scale enterprises co-operating with a medical university].

This descriptive study reports the results of a systematic survey on occupational safety and health hazards and risks to exposed workers at companies co-operating with a medical university, and investigates the effective methods for their management. Varieties of works at all these co-operating companies have been categorized into 14 types of businesses. The survey was performed in two-fold; an individual interview of managers and a comprehensive inspection of workshops, and a questionnaire to all workers (response rate 95.9%). All of the co-operating companies were small-scale enterprises with less than 50 employees. The occupational safety and health risks to be controlled were accidental contact with biomedical wastes, heat in the kitchen, laundry and boiler room, unfavorable ventilation at workplace close to medical facility, and physical fatigue of guards and janitors. A higher number of occupational health physicians and a higher rate of health examinations were observed compared to other small-scale enterprises in Japan. About 80% of all workers were conscious of working on the premises of medical facilities. To improve the occupational safety and health activities of co-operating companies, we propose the use of professionals at the medical university, the promotion of joint activities among the co-operating companies, and the strengthening of mutual connection and coordination between the co-operating companies and the medical university.

Noise attenuation characteristics of a foam type earplug measured using a dummy head.

The attenuation characteristics of the earplug using a dummy head (KEMAR; Knowles Electronics Manikin for Acoustic Research) were measured, when it was exposed to pure tones or broadband noises at three different sound pressure levels (SPLs) of 70, 80 and 90 dB SPL in the 'wide frequency range from 250 to 20 k Hz. We ascertained the satisfactory capacity of noise attenuation except for from 10 k to 14 k Hz. The noise attenuation level increased with frequency until 2 k Hz, became almost constant until 8 k Hz, then decreased at around 10 k to 14 k Hz, and recovered in the range from 16 k to 20 k Hz. The frequency characteristics were identical among three different sound pressure levels and almost identical between pure tones and broadband noises. The change of frequency characteristics affected by the depth of the earplug that was inserted into the artificial ear canal of the KEMAR was also investigated. Measured sound pressure level by the builetin microphone in the KEMAR revealed a region in which the measured sound pressure levels were relatively higher around 10 k Hz. The frequency of the region moved higher when the earplug was inserted more deeply. Therefore it was considered that this phenomenon was related to the resonance frequency of the cylinder-like cavity made between the end section of the earplug and the diaphragm of the built-in microphone.