Concern over the effects on humans of ELF- (extremely low frequency; less than 300 Hz) electromagnetic fields has rapidly increased in recent years. The effects seem to be related to gene level aberrations such as carcinogenesis and developmental malformations, but it is difficult to obtain experimental evidences on field effects. Several safety guidelines or permissible doses have been proposed for electromagnetic wave, but they mainly cover the range of microwave frequencies. Three of the guidelines made in 1989-1990 included ELF-electromagnetic fields and two newly approved guidelines on power-frequency electromagnetic fields appeared in 1990. However, they adopted considerably different values based on different theoretical standpoints. Generally, the concept of electromagnetic fields appears to be confused with that of magnetic field and thus the ideas for protective measures conflict between the two. The author first presented the concepts of electromagnetic and magnetic fields, then briefly discussed their biological effects together with the underlying mechanism, and lastly described these drafts on safety standards or permissible doses. Since subtle and difficult problems remain to be resolved, further investigation will be required in order to put these guidelines into practice.

View full abstract

Using a Holter electrocardiograph (ECG), we recorded the heart rates of ward nurses by working hours and nursing activity. Energy expenditure was calculated from the heart rate data and nurse work lord was evaluated. The following results were obtained.
1) Average heart rates were 77 (beats/min) for day-shift nurse in surgical ward, 76 for evening-shift nurse in mixed, ward, and 74 for night-shift nurse in mixed ward.
2) The energy expenditures per day were calculated to be 3, 474 kcal for day-shift nurse in surgical ward, 3, 060 kcal for evening-shift nurse in mixed ward, and 3, 238 kcal for night-shift nurse in mixed ward.
3) The energy expenditures during working hours were 2, 110 kcal/510 min for day-shift nurse in surgical ward, 1, 805 kcal/495 min for evening shift nurse, and 2, 014 kcal/570 min for night-shift nurse in mixed ward.
4) The highest energy expenditures of nurse engaged in direct nursing care were 834 kcal (39.5%) for day-shift nurse in surgical ward, 632 kcal (34.9%) for evening-shift nurse in mixed ward, and 790 kcal (39.2%) for night-shift nurse in mixed ward.
5) The longest working hours were 174 min (34.1%) in assisting with medical examinations and treatment by day-shift nurse, 155 min (31.3%) in direct care by evening-shift nurse, and 222 min (39.0%) by night-shift nurse.
The results indicate that the energy expenditure calculated from the average heart rate of ward nurses in higher than that of other types of workers. The reason for this difference is discussed in this report. Also, this study showed that the energy expenditure determined by this method does not necessarily increase in proportion to working hours.

View full abstract

This study was conducted to evaluate the relationship between the prevalence of subjective symptoms in workers using vibrating tools and the duration of chain saw operation and to examine whether the symptoms were relevant to factors other than the usage of vibrating tools. The statistical model of multivariate analysis was adapted to analyze individual data on the subjective symptoms of 317 chain saw operators. The obtained results were as follows:
1. In analysis of covariance, age-adjusted operating year in workers with peripheral circulatory, peripheral neurological and musculoskeletal disturbances was significantly longer than that without such disturbances. For these disturbances, partial regression coefficients of operating year were significantly high in multiple regression analysis. These results show that these disturbances and age-adjusted operating year are mutually closely related.
2. Multiple regression analysis showed that the partial regression coefficients of both operating year and age were low for nine symptoms, i.e. dulling sense of touch, joint pain, headache, dizziness and/or tinnitus, profuse sweating, discomfort of stomach, palpitation and/or dyspnea, hearing disturbance and lumbago. These results suggest that such symptoms were not related to either age or chain saw operation.
3. The results of principal component analysis were visualized in three-dimensional space in order to evaluate the relationships among the symptoms. The analysis showed that peripheral circulatory and neurological disturbances appeared independently and that general symptoms such as easy fatigability, headache, forgetfulness, vertigo and/or tinnitus, easy irritability, sleep disorder, profuse sweating, discomfort of stomach, palpitation and/or dyspnea, shoulder stiffness, hearing disturbance and lumbago consisted of four independent groups. Each group has no relationship with duration of chain saw operation. This suggests other harmful factors of the groups play a role in the prevalence of the symptoms.

View full abstract

We investigated the relationship between serum creatine phosphokinase (CPK) activity and energy expenditure in young adults and evaluated whether serum CPK activity is a useful index of energy expenditure. These data were obtained from 225 (men: 94, women: 131) healthy young adults.
The results of the survey were as follows:
In men, there was a statistically significant correlation between serum CPK activity and energy expenditure (r=0.370; p<0.01; y=1986.0+8.2x), energy expenditure/body weight (r=0.270; p<0.01; y=35.4+0.06x) and daily activity index (r=0.357; p<0.01; y=0.38+0.0030x)
In women, there was a statistically significant correlation between serum CPK activity and energy expenditure (r=0.207; p<0.05; y=1895.0+3.0x), and daily activity index (r=0.194; p<0.05; y=0.432+0.0017x). The higher the proportion of exercising subjects, the higher was the serum CPK activity.
These results suggest that measurement of serum CPK activity can be used to evaluate energy expenditure.

View full abstract

Recently medical services and nursing system are being reformed due to high medical costs and shortage of clinical nurses. The shortage of clinical nurses influences not only their working conditions but also their own health problems. In European countries and the United States, low back pain (LBP) has been reported to be one of the most common and costly health problems among clinical nurses.
To estimate the occupational risk factors of LBP among nurses, a questionnaire survey of LBP and occupational risk factors was carried out in 1987 on 947 clinical nurses and as well as on 300 female clerical workers of three local goverments. First, to examine the prevalence and the magnitude of the problem, we analyzed several kinds of prevalence rates of LBP and its characteristics among nurses and clerical workers. Second, a case-control study was conducted to investigate the relationship between LBP and occupational risk factors. In analyzing occupational risk factors of LBP, odds ratios, age adjusted odds ratios and 95% confidence intervals were computed. Finally, to estimate simultaneously the effect of multiple risk factors of LBP and to confirm univariate age adjusted odds ratio analyses, several multivariate analyses were performed.
Point, period (a month), and lifetime prevalence rates of LBP and prevalence rate of severe LBP among clinical nurses were significantly higher than those of clerical workers (p<0.05-0.001, respectively). Demographic and occupational items, such as being an assistant nurse (as opposed to a registered nurse), and working in certain departments (internal medicine, orthopedic surgery, neurosurgery, psychiatry, tuberculosis ward) showed significantly higher odds ratios for LBP (p<0.05-0.001, for all). Many items pertaining to working conditions connected with shift work, hospitalized conditions of patients, taking breaks and holidays, working postures, weight of patients and equipment lifting and moving, working environments and so on had significantly elevated age adjusted odds ratios (p<0.05-0.001, for all). Intensity of work loads estimated subjectively such as ‘caring for patients who are in bed’, ‘supporting patients when transporting and bathing them’, ‘preparing drugs and injections, and treating’, ‘observing and monitoring patients' conditions’, ‘instructing and explaining procedure to patients and their family’ and so on also had significantly elevated age adjusted odds ratios (p<0.05-0.001, for all). Moreover, many items on the problems connected with working life and interpersonal relationships showed significantly higher age adjusted odds ratios (p<0.05-0.001). In multivariate analyses, independent variables which made a significant contribution to the model were similar to the items which had significantly elevated age adjusted odds ratios. In summarizing these results, many independent variables were related to shift work, physical nursing work loads and mental stress in caring for patients. It is noteworthy that not only direct influences from occupational factors but also indirect influences from their effects on workers' lives were observed.
These results suggest a positive relationship between nursing work load and LBP. Therefore, it is recommended that working conditions and work loads of clinical nurses as mentioned above be improved in order to prevent LBP and promote the quality of nursing services.

View full abstract