Relationship between uptake and elimination of toluene and debrisoquin hydroxylation polymorphism.

The toxicokinetics of toluene were studied in six healthy subjects. Three of the subjects were phenotyped as rapid hydroxylators of debrisoquin and three subjects were phenotyped as slow hydroxylators of debrisoquin. The subjects were exposed in an exposure chamber to toluene vapor (3.25 mmol/m3) for 4 hours. Solvent concentrations in blood and the metabolites, hippuric acid and o-cresol, in urine were measured during the exposure period and 3 hours after exposure. The capacity to metabolize debrisoquin was determined in three volunteers who had earlier experimentally been exposed to toluene. The uptake of toluene was about 3 mmol, or 50% of the inhaled dose in both rapid and slow hydroxylators. There were no significant differences between the two phenotypic groups with regard to concentrations of toluene in blood, apparent blood clearance of toluene, or excretion of hippuric acid and o-cresol.

Percutaneous uptake and kinetics of methyl isobutyl ketone (MIBK) in the guinea-pig.

Continuous intravenous infusion of 0.478 mumol/min methyl isobutyl ketone (MIBK) was performed for 30 min in pentobarbital-anesthetized guinea-pigs. Epicutaneous exposure for 150 min was carried out 2.5 h later after administration of MIBK to a sealed glass ring on the clipped back of the animals. Arterial blood was analyzed for MIBK by gas chromatography. Blood clearance averaged 201 ml.min-1.kg-1 body wt. A maximum percutaneous uptake of 1.1 mumol.min-1.cm-2 was reached 10-45 min after the onset of exposure and decreased to 0.56 mumol.min-1.cm-2 during the latter part of exposure.

Reproducibility of a questionnaire for assessment of physical load during work and leisure time. Stockholm MUSIC I Study Group. MUSculoskeletal Intervention Center.

A self-administered questionnaire on physical load in lifetime occupational work, in present job, and in present leisure activities was tested for reproducibility with the test-retest method in 126 male and 217 female workers from 30 occupations. The questionnaire contained 92 questions and nine different response scales. The results indicated that questions concerning physical activity retrospectively and in the present job, vibrations in the present job, working postures involving the whole body, and questions concerning specific leisure activities (eg ball games, skiing, etc) seem to offer sufficient reproducibility to be worth testing for validity, at least at a 5-point ordinal level. Questions concerning working postures involving parts of the body, including awkward postures, and questions concerning manual materials handling seem to offer too poor reproducibility to be used in studies in which the aim is to quantify duration in proportions of a typical working day and frequencies in times per hour. Questions concerning level of physical activity and exertion in domestic work seem to offer too poor reproducibility to be used at a 5-point ordinal level. Gender, age, and musculoskeletal complaints did not influence the reproducibility to any great extent.

Can cardiovascular load in ergonomic epidemiology be estimated by self-report? Stockholm MUSIC 1 Study Group.

In ergonomic epidemiology exposure to local loads as well as cardiovascular load may contribute to general and local fatigue and musculoskeletal disease. Self-reported exposure is often the only feasible method in large population studies. The aim of this study was to evaluate retrospectively self-reported physical activity and perceived exertion as estimates of cardiovascular load during occupational work. The study population consisted of 39 men, representing 25 different occupations, and 58 women, representing 28 occupations. Ratings of physical exertion (RPE scale) and physical activity (Edholm scale transferred to multiples of the basal metabolic rate, METs) at the end of a work shift were correlated with the average heart rate during the same work shift. In the male population, both RPE ratings and METs correlated significantly (P < .01) with the average heart rate. No such correlation was observed in the female population.

Self-reported physical exertion in geriatric care. A risk indicator for low back symptoms?

STUDY DESIGN: The study group consisted of 131 female nursing aides who took part in an intervention program with physical training or education. Assessments were performed before the intervention program and after 6 months. At follow-up evaluation, 91 nursing aides remained in the study. OBJECTIVES: To examine if perceived physical exertion was a risk indicator for low back symptoms, and to examine the relationship between perceived physical exertion, aerobic capacity, back endurance, psychological demands, and job control. SUMMARY OF BACKGROUND DATA: Perceived physical exertion frequently is assessed in epidemiologic studies concerning low back symptoms. More information about the relationship between perceived exertion, other potential risk indicators, and symptoms may provide opportunities for effective prevention of symptoms. METHODS: Assessments were obtained by questionnaires and physical capacity tests. RESULTS: The nursing aides who reported high physical exertion and were 45 years of age or older were at greater risk in the follow-up period for reporting new symptoms, continued symptoms with the same intensity, or more intense symptoms from the low back (rate ratio, 3.01; 95% confidence interval, 1.1-8.2). The exposure variable correlated most strongly (r = 0.4) with perceived physical exertion was psychological demands. CONCLUSIONS: The results indicated being aged 45 years or older, combined with high perceived physical exertion, was a risk indicator for low back symptoms. A relationship between perceived physical exertion and psychological demands was observed, but there was no influence of physical capacity on perceived physical exertion.

To what extent do current and past physical and psychosocial occupational factors explain care-seeking for low back pain in a working population? Results from the Musculoskeletal Intervention Center-Norrtälje Study.

STUDY DESIGN: A population-based case referent study. OBJECTIVES: To determine whether current and past physical and psychosocial occupational factors are associated with care-seeking for low back pain in working men and women. SUMMARY OF BACKGROUND DATA: The importance of physical and psychosocial workloads as causal factors of low back pain has mostly been investigated in special occupational groups and with a cross-sectional design, which makes generalizability and interpretations more difficult. METHODS: The study comprised 2118 working men and women 20 to 59 years old (695 cases, and 1423 referents). Cases were defined as persons seeking care by any caregiver for low back pain. The exposure assessments were made through questionnaires and interviews about current and past physical and psychosocial loads during work and leisure time. RESULTS: In a logistic regression analysis, physical load from forward bending in men (RR = 1.8) and high physical load, in general, in women (RR = 2.0) showed increased relative risks. Psychosocial factors alone seemed to be of less importance in women, but "poor job satisfaction" and "mostly routine work without possibilities of learning" increased the risk in men. Combined current and past exposures further increased the risks. A combination of high physical and psychosocial loads increased the risk substantially, but few were exposed to such loads. Adjustment for lifestyle and other loads outside work did not change the results. CONCLUSION: Current and past physical and psychosocial occupational factors, both separately and combined, seem to be gender-specific, and to have a moderate impact on care-seeking for low back pain in a general working population.

Measuring and characterizing force exposures during computer mouse use.

OBJECTIVES: The purpose of this study was to develop and validate a sampling strategy for characterizing the finger force exposures associated with computer mouse use. METHODS: Mouse forces were measured from 16 subjects (8 men, 8 women), on 3 separate days, at their actual workstations while they performed (i) their regular work, (ii) a battery of standardized tasks, and (iii) simulated mouse use. RESULTS: The forces applied to the mouse did not vary between hours or days. During regular work, the mouse was used 78.0 (SD 40.7) times per hour, accounting for 23.7 (SD 9.5)% of the worktime. The mean forces applied to the sides and button of the mouse were low, averaging 0.6 % (0.35 N) and 0.8 % (0.43 N) of the maximal voluntary contraction, respectively. The forces applied to the mouse during the standardized tasks differed from the regular work forces; however, there were moderate-to-strong correlations between the 2 measures. CONCLUSIONS: With respect to performing exposure assessment studies, the 3 major findings were (i) mouse force measurements should be made while subjects perform their actual work in order to characterize the absolute applied force accurately, (ii) the forces applied to the mouse during the performance of a short battery of standardized tasks can be used to characterize relative exposure and identify computer operators or work situations for which higher forces are applied to the mouse, and (iii) subjects cannot accurately simulate mouse forces.

HARBO, a simple computer-aided observation method for recording work postures.

OBJECTIVES: The aim of the study was to present an observation method focusing on the positions of the hands relative to the body and to evaluate whether this simple observation technique gives a reliable estimate of the total time spent in each of five work postures during one workday. METHODS: In the first part of the study the interobserver reliability of the observation method was tested with eight blue-collar workers. In the second part the observed time spent with work above the shoulder level was tested in relation to an upper-arm position analyzer, and observed time spent in work below knuckle level was tested in relation to a trunk flexion analyzer, both with 72 blue-collar workers. RESULTS: The interobserver reliability for full-day registrations was high. The intraclass correlation coefficients ranged from 0.99 to 1.00. The observed duration of work with hands above shoulder level correlated well with the measured duration of pronounced arm elevation (> 75 degrees). The product moment correlation coefficient was 0.97. The observed duration of work with hands below knuckle level correlated well with the measured duration of pronounced trunk flexion angles (> 40 degrees). The product moment correlation coefficient was 0.98. CONCLUSION: The present observation method, designed to make postural observations continuously for several hours, is easy to learn and seems reliable.

The accident process preceding overexertion back injuries in nursing personnel. PROSA study group.

OBJECTIVES: This prospective dynamic-population-based study investigated factors involved in the accident process preceding overexertion back injuries among nursing personnel. METHODS: The study covered all reported occupational overexertion back injuries due to accidents among of the approximately 24 500 nurses in the Stockholm County hospitals during 1 year. It was assumed that several factors interact in the accident process. Detailed information was obtained for each injury by interviews with the injured nurse and head nurse. Risks in the physical environment were identified using an ergonomic checklist. RESULTS: During the study 136 overexertion back injuries were reported. Of the 130 nurses participating in the study, 125 had been injured in connection with patient work. Cluster analysis yielded 6 clusters and their pattern of contributing factors. The most frequent injury occurred during patient transfer in the bed or to or from the bed, without the use of transfer devices, when the patient suddenly lost his or her balance or resisted during the transfer and the nurse had to make a sudden movement. However, there were physical conditions, such as shortcomings in the physical work environment or a lack of a transfer device, that compelled the nurses to perform the tasks under unsafe conditions. CONCLUSIONS: The clusters showed a complexity of different kinds of accidents and indicated that the measures for preventing accidents, or for blocking an accident process once started, have to be of different kinds and placed at several different levels in the organization of a workplace.

The prevention of back injuries in Swedish health care--a comparison between two models for action-oriented feedback. PROSA Study Group.

This paper considers two different models for action-oriented feedback designed to prevent back injuries in Swedish health care. Feedback was provided by physiotherapists/ergonomists from Occupational Health Services. The models tested were feedback to work groups, and feedback solely to supervisors. Both generated a considerable number of accident-prevention proposals. Proposals of supervisors were implemented to a greater extent. Supervisors tended to advocate training, while work groups were more concerned with improved technical aids. Otherwise, only minor differences were detected between the models in application. The active involvement promoted by feedback, in particular to work groups, was considerable.

Validity of self-reported duration of work postures obtained by interview. MUSIC-Norrtälje Study Group.

The aim of the study was to validate interview data concerning the duration of four work postures (1) sitting, (2) standing/walking with hands above shoulder level, (3) standing/walking with hands between shoulder and knuckle level, and (4) standing/walking with hands below knuckle level. The self-reported time spent in each posture was tested in relation to observations and technical measurements in 20 subjects during two full working days. The linear relationships between self-reports and observations were strong for the three postures; sitting (r2 = 0.55), hands above shoulder level (r2 = 0.58) and hands below knuckle level (r2 = 0.69). Thus, using this interview technique, self-reports concerning time spent in (1) sitting, (2) standing/walking with hands above shoulder level and, (3) standing/walking with hands below knuckle level may be accurate enough for studying these work postures in epidemiological studies.

Influence of cigarette smoking on the toxicokinetics of toluene in humans.

To study the influence of cigarette smoking on the toxicokinetics of toluene, 10 habitual smokers who intended to stop smoking were exposed to toluene vapor (3.2 mmol/m3, 4 h) at three different exposure occasions: (I) while the smoking habit was still ongoing, and (II and III) 1 and 3-4 wk, respectively, after the day at which the smoking habit was discontinued. Solvent concentrations in the exhaled air and in the blood as well as hippuric acid concentrations in the urine were measured during the exposure period and for 3 h after the exposure period. The apparent clearance of toluene decreased significantly (p less than 0.05) 3-4 wk after the smoking habit was discontinued. This decrease was not a consequence of the increased body weight noticed in the subjects. No statistically significant differences between the three exposure occasions in the elimination rate of hippuric acid could be demonstrated. Thus, cigarette smoking seems to enhance the elimination rate of toluene from the body, since the apparent clearance was decreased after smoking was stopped.

Exposure to methyl isobutyl ketone: toxicokinetics and occurrence of irritative and CNS symptoms in man.

The toxicokinetics as well as irritative effects and CNS symptoms of methyl isobutyl ketone (MIBK) were studied in human volunteers during inhalation exposure. The volunteers were exposed (2h, 50 W) in an exposure chamber on four different occasions to about 10, 100 and 200 mg/m3 MIBK and to a combination of about 100 mg/m3 MIBK and 150 mg/m3 toluene. The relative pulmonary uptake of MIBK was about 60% and the total uptake increased linearly with increasing exposure concentration. The concentration of MIBK in blood rose rapidly after the onset of exposure and no plateau level was reached during exposure. No tendency for saturation kinetics could be observed within the dose interval and the apparent blood clearance was 1.61/h/kg at all exposure levels. The concentration of unchanged MIBK in the urine after exposure was proportional with the total uptake. Only 0.04% of the total MIBK dose was eliminated unchanged via the kidneys within 3 h post exposure. The concentrations of the metabolites 4-hydroxy-4-methyl-2-pentanone and 4-methyl-2-pentanol were below the detection limit (5 nmol/l). Irritative and CNS symptoms occurred during exposure. The degree of both irritative and CNS symptoms increased during exposure to 100 and 200 mg/m3 compared with 10 mg/m3, but combination exposure with toluene exhibited the most pronounced effect. There were no significant effects from exposure on the performance of a simple reaction time task or a test of mental arithmetic.

Gender differences in musculoskeletal health of computer and mouse users in the Swedish workforce.

The objectives of the study were to explore the musculoskeletal health of computer users in the Swedish workforce with regard to gender and psychosocial factors, and to describe gender differences between the occupational groups. A subset was chosen from a large survey of 12,462 individuals representing the workforce of Sweden, performed by Statistics Sweden. Included in the subset were 2044 subjects who worked for at least half their working hours with personal computers, or an equivalent device, and also used a computer mouse. All occupational groups had prevalence ratios (women/men) > 1. When using regression models, the variables 'learn and develop' and 'involved in planning your work' were health factors, and 'too much to do' was a risk factor for upper body symptoms for both women and men. For women 'PC duration 100' was a risk factor and 'support from superiors' was a health factor. Age seemed to be a stronger risk factor for men than for women.

Occupational and individual factors related to musculoskeletal symptoms in five body regions among Swedish nursing personnel.

The relationship between individual factors, physical and psychosocial exposure at work, and musculoskeletal symptoms in the neck, shoulders, low back, hands, and knees was studied among female nursing personnel working at a Swedish hospital. The personnel had participated in a course in work technique (patient transfer and handling principles). Prior to the course, the subjects had filled in a questionnaire (n = 688). The aim of this cross-sectional study was to elucidate whether different individual and work factors are related to musculoskeletal symptoms in a specific body region. Due to the cross-sectional design, however, causality cannot be discussed. Univariate analyses and multiple logistic regression analyses were performed and yielded similar results. The latter analyses showed that in the present hospital setting, individual factors together with physical and psychosocial work factors were related to symptoms in the neck, low back, and hands; individual factors and psychosocial work factors were related to symptoms in the shoulders; while only individual factors were related to symptoms in the knees. The results of the present study showed that various individual factors and physical and psychosocial work factors were related to musculoskeletal symptoms in the different body regions. Thus, the identification of risk factors might have far-reaching implications for the way in which effective health programs for prevention should be designed in the hospital setting.

Dietary and ethanol induced alterations of the toxikokinetics of toluene in humans.

This study was undertaken to evaluate the influence of a carbohydrate restricted diet, a subacute ethanol intake, and their combined effect on the kinetics of toluene in humans. Eight healthy male volunteers were exposed by inhalation at four different occasions to 200 mg/m3 2H8-toluene for two hours at a work load of 50 W after a one week low (30%) carbohydrate (CH) diet or high (60%) CH diet with (+EtOH) or without (-EtOH) ethanol consumption (47 g ethanol) on the evening before exposure. Deuterium labelled toleune was used to measure the excretion of hippuric acid originating from toluene separately from hippuric acid from other sources. The results indicated that subacute ethanol consumption combined with a carbohydrate restricted diet, may enhance the metabolism of toluene in humans at an exposure concentration of 200 mg/m3. The cumulative amount of hippuric acid excreted in the urine up to 20 hours after the end of exposure in % of the net uptake of toluene was enhanced by 22% (p = 0.05) in the low CH + EtOH compared with the low CH-EtOH experiment. The apparent blood clearance of toluene was 37% higher in the low CH + EtOH than in the low CH-EtOH experiment, but this effect was not statistically significant (p = 0.1). There were no significant changes in the kinetics of toluene as a result of a low carbohydrate diet alone. Neither did subacute ethanol intake without the combination with a carbohydrate restricted diet influence the kinetics of toluene.

Risk indicators for reported over-exertion back injuries among female nursing personnel.

We conducted a case-referent study to identify and quantify work-related and non-work-related risk indicators for reported over-exertion back injuries among nursing personnel. The source population was all nursing personnel employed in the Stockholm County hospitals during a 32-month period. The 240 cases and 614 referents completed questionnaires about occupation, type of clinic, working hours, shift work, patient transfers, perceived exertion, back pain, prior back injury, job strain, body mass index (BMI), smoking, immigrant status, physical training, and self-rated fitness. The highest relative risks (RR) were observed for work-related factors: working at an orthopedic clinic (RR = 5.2; 95% CI = 2.7-10.2), > or =1 patient transfer/shift (RR = 2.7; 95% CI = 1.6-4.5), and working full-time (RR = 2.4; 95% CI = 1.6-3.6). Training in the use of transfer devices, and regular use of transfer devices, reduced the relative risk from patient transfer. Among the non-work-related factors, only body mass index > or =25 kg/m2 and immigrant status was associated with a slight increase in relative risk.

Rehabilitation of neck-shoulder pain in women industrial workers: a randomized trial comparing isometric shoulder endurance training with isometric shoulder strength training.

OBJECTIVES: To study whether isometric shoulder endurance was more advantageous than isometric shoulder strength training in reducing pain and perceived exertion and to increase shoulder function through improved muscle endurance and strength. DESIGN: Randomized trial. SETTING: Three occupational health care centers. PARTICIPANTS: Women industrial workers with nonspecific neck-shoulder pain. The International Classification of Diseases, 10th Revision (ICD-10) diagnosis was "cervicobrachial syndrome" (M53.1). Thirty-eight patients completed the isometric shoulder endurance training and 31 patients completed the isometric shoulder strength training. INTERVENTION: Twelve weeks of training. MAIN OUTCOME MEASURES: Self-reported pain and rating of perceived exertion (RPE), arm motion performance test, shoulder muscle strength, shoulder muscle endurance, and shoulder functional tests, as well as follow-up after supervised training had ended. RESULTS: The isometric shoulder strength training resulted in an almost one-scale step decrease in RPE at work and a 5% to 15% improvement of arm motion performance compared with the endurance training. The isometric shoulder strength training more effectively improved left side shoulder abduction strength (p < .026), but no major differences were found for the other strength measurements. The isometric shoulder endurance training was not more successful than the strength training in the endurance test (p .51 to .81). CONCLUSIONS: Physical training programs for neck-shoulder pain may include isometric shoulder muscular strength exercise in addition to isometric shoulder endurance training, rather than endurance training only.