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Magnetic fields of video display terminals and spontaneous abortion.

The aim of this study was to examine whether work with a video display terminal and exposure to the magnetic fields of video display terminals are related to spontaneous abortion. The study was conducted among women employed as bank clerks and clerical workers in three companies in Finland. The cases (191 spontaneous abortions) and controls (394 births) were identified from Finnish medical registers for the years 1975-1985. Use of video display terminals was defined using the workers' own reports and information provided by the companies. The assessment of exposure to the magnetic fields was based on measurements of the fields of video display terminals. The odds ratio for spontaneous abortion for working with video display terminals was not increased (odds ratio = 1.1, 95% confidence interval 0.7-1.6). However, the odds ratio for workers who had used a video display terminal with a high level of extremely low frequency magnetic fields (> 0.9 microT) was 3.4 (95% confidence interval 1.4-8.6) compared with workers using a terminal with a low level of these magnetic fields (< 0.4 microT). Adjustment for ergonomic factors and mental work load factors changed the odds ratio for magnetic field exposure only very slightly. The findings suggest the need for future studies with assessment of exposure to the magnetic fields in the actual working environment to confirm the possible risk.

Abortion, Spontaneous

[The morbidity characteristics of workers in an information reference service employed at video terminals].

Female telephone operators working with displays perform monotonous operations which cause marked hypodynamia. A study was performed to investigate the labour conditions, which revealed respiratory diseases as the main cause of morbidity with temporary disability. Extensive medical examinations also showed the prevalence of gynaecological disorders resulting from the working posture and hypodynamia. Laboratory tests revealed marked changes in the peripheral blood system. The questionnaire analysis performed showed the prevalence of complaints of asthenic manifestations and excessive fatigability by the end of the working shift.

Absenteeism

Human electroretinogram responses to video displays, fluorescent lighting, and other high frequency sources.

Time-averaged human electroretinogram (ERG) responses were determined for several workplace visual stimuli which are temporally modulated at rates exceeding the perceptual critical fusion frequency (CFF). A clearly identifiable synchronous response was in evidence for a video display terminal (VDT) stimulus operating with a refresh rate as high as 76 Hz. A directly viewed fluorescent luminaire with controllable driving frequency elicited a synchronous response at rates as high as 145 Hz. In addition, an intense stimulus created by modulating the light from a slide projector produced responses at least as high as 162 Hz. The implications of these high-frequency responses are representing a potential basis for visual symptoms are discussed.

Adult

[The dependence of the degree of visual fatigue on the shift duration in work with video terminals and an assessment of the efficacy of preventive measures].

Dynamic studies of visual capacity for work in individuals working with displays revealed decreased accommodation volume after the long concentration on the display. The total time of work with the display of more than 2h a day involved a decrease of the accommodation volume by 0.42-0.49 diopters and transitory myopia of 0.15-0.21 diopters, as well as increased self-appraisal of fatigue. The system of prophylactic measures including rest breaks, special exercises, massage was worked out and put into practice. Repeated study has proved the effectiveness of suggested measures.

Accommodation, Ocular

Occupational risk factors for congenital heart disease.

To investigate possible associations between cardiovascular malformations and maternal occupational exposure to various factors during the first trimester of pregnancy, 406 cases and 756 controls were studied retrospectively. The cases were taken from all infants diagnosed with cardiovascular malformations born in Finland during 1982 and 1983. The controls were randomly selected from all normal births in the country during the same period. All mothers were interviewed approximately 3 months after delivery by a midwife, using a structured questionnaire. Maternal overall exposure to chemicals at work was more prevalent among the case group (35.8%) than the control group (26.2%, P less than 0.01). Among the specific chemical groups, maternal exposure to dyes, lacquers, or paints was significantly associated with the risk of congenital heart disease. Exposure to organic solvents during the first trimester seemed to increase to risk of ventricular septal defect (P less than 0.05). Work at video display terminals was slightly more prevalent among the case group (6.3%) than among the control group (5.0%). The mothers' education level, regular exposure to passive smoking at work, or temperature at the workplace were not risk factors for congenital heart disease in the offspring, neither was maternal exposure to microwave ovens, disinfectants, pesticides, or anesthetic gases. It is concluded that many maternal exposures at work seem not to have a teratogenic effect on the fetal heart, although the limited power of this investigation needs to be borne in mind.

Case-Control Studies

The Video Display Terminal Eye Clinic: clinical report.

The Video Display Terminal Eye Clinic was designed to relieve the symptoms of video display terminal users by diagnosing and treating visual problems and by analyzing the patients' work station environment through an in-office simulation and making suggestions for improvements. The Clinic was open to the public and patients were therefore self-selected. The symptoms, diagnoses, and treatments were compiled retrospectively and reported for 153 patients. Vision problems were diagnosed in most patients. The most frequent diagnoses included: presbyopia, improper spectacle design for presbyopia, accomodative deficiencies, esophoria, exophoria, and hyperopia. The results suggest that proper visual care and work station arrangement can improve comfort.

Accommodation, Ocular

The three most common occupational exposures reported by pregnant women: an update.

Many uncertainties exist in regard to counseling women with occupational exposures during pregnancy. This is due to limited knowledge of the reproductive toxicologic effects of industrial agents, lack of safety standards aimed at protecting the fetus, and limitations in assessing the extent of exposure. The approach to this subject taken by the Motherisk Program and a review of the three most common occupational exposures are presented. Epidemiologic studies and measurements of radiation do not suggest a reproductive hazard for video display terminals. Exposure to organic solvents is hard to quantitate, and information is sparse and sometimes contradictory, and therapeutic decisions are difficult to reach. To date there is no convincing evidence that working with organic solvents within safety regulations would harm a fetus, in contradistinction to detrimental fetal effects of solvent abuse. The reproductive risks of lead are well documented, fetal exposure can be assessed, and effective treatment exists, but its effects on the pregnancy have not been fully established. However, new evidence suggests that maternal levels that are much lower than the accepted adult limits may be damaging to the fetus.

Computer Terminals

The effects of VDT data entry work on operators.

The before/after study of physiological and biochemical parameters was used to delineate the effects of VDT data entry work on operators. Twenty-nine healthy Chinese students were chosen and divided at random into the simple and the complicated data entry group. The subjects were instructed to work as quickly and correctly as possible according to the 'Data Entry Work Programme' for 150 min. Work performance (correct entry) was automatically recorded once every 10 min. The before/after parameters were tested respectively. The results showed that performance fluctuated over time. It decreased obviously after 50-60 min of work, followed by a rebound, and there was a terminal motivation phenomenon at the end of the test, which was associated with the auto-arousal and cerebral compensatory effort. Changes in physiological parameters revealed that operators were fatigued after data entry work. The adrenaline excretion in urine showed a tendency to increase after simple data entry work. The noradrenaline excretion showed a tendency to decrease after complicated data entry work. The differences in performance, diastolic blood pressure in a standing position and neurobehaviour between two groups indicated that much stress was experienced when performing complicated data entry work.

Adult

Musculoskeletal disorders among visual display terminal users in a telecommunications company.

The relationship between workplace factors and work-related upper extremity musculoskeletal disorders (UE disorders) was assessed in a cross-sectional study of 533 telecommunication employees utilizing video display terminals (VDTs). Cases of UE disorders were defined using symptom questionnaires and physical examinations. Data on demographics, individual factors (medical conditions and recreational activities), work organization and practices, and psychosocial aspects of work, including electronic performance monitoring (EPM), were obtained by questionnaire. Associations between workplace factors and UE disorders were assessed by multiple logistic models generated for each of the four UE areas (neck, shoulder, elbow, hand/wrists). One-hundred and eleven (22%) participants met our case definition for UE disorders. Probable tendon-related disorders were the most common (15% of participants). Probable nerve entrapment syndromes were found in 4% of participants. The hand/wrist was the area most affected, 12% of participants. The following variables had associations in the final models (p < 0.05) with at least one of the four UE disorders, although the strength of these associations were modest. Non-white race, a diagnosis of a thyroid condition (self-reported) use of bifocals at work, and seven psychosocial variables (fear of being replaced by computers, increasing work pressure, surges in workload, routine work lacking decision-making opportunities, high information processing demands, jobs which required a variety of tasks and lack of a production standard) were associated with UE disorders. This study indicates that work-related UE musculoskeletal disorders are relatively common among telecommunication workers who use VDTs, and adds to the evidence that the psychosocial work environment is related to the occurrence of these disorders.

Adult

Task variables and visual discomfort associated with the use of VDT's.

We investigated task variables that may influence the incidence of visual discomfort amongst subjects who routinely spent a proportion of their day working with visual display terminals (VDT's). A diary was kept by subjects over five consecutive working days, in which they recorded visual symptoms, the visual tasks undertaken, the amount of time spent on workbreaks, work pressure, work interest, and personal moderating factors which may have influenced the symptoms recorded. The symptoms recorded by subjects were then treated as dependent variables in multiple regression analyses with the diary findings (task-related factors) as independent variables. The incidence of some types of symptoms was significantly associated with specific categories of work tasks, personal moderating influences, work pressure, work interest, time of day, and day of week.

Adult

Visual performance at video display terminals--effects of screen color and illuminant type.

A limited set of illuminants and phosphor colors are commonly used in video display terminal (VDT) working environments. This study attempts to identify any combinations of such conditions that influence performance on a visually demanding counting task. Experiments were performed to test whether the phosphor color, ambient lighting spectrum, or temporal frequency characteristics of the display and ambient lighting could alter performance. Under conditions where potentially contaminating variables such as reflectance level and screen glare patterns were equalized, no significant differences in performance were produced by the particular sets of stimulus conditions tested. The results suggest that displays and illuminant types that are in common use allow substantially equivalent visual performance.

Adult

Distinguishability of the video display terminal (VDT) as a source of magnetic field exposure.

Magnetic field strength or its surrogate has been used as the measurement of exposure in all studies involving field exposure. Video display terminals (VDTs) are considered a minor source on this scale because its field strengths lie in the low range of magnetic fields. Several experiments show, however, that field strength may not be the only relevant variable in determining exposure. This paper explores the use of a method based on "effects functions" to determine the extent to which the VDT can be distinguished from other sources. It is shown that VDT exposure may be of consequence if exposure depends on certain types of time variation of the field. Because of the incompleteness of science in this area, this is a demonstration of a method rather than an actual demonstration of VDT as a significant source of exposure.

Computer Simulation

ELF magnetic field exposures in an office environment.

Potential exposures to extremely low frequency (ELF) magnetic fields were investigated in response to worker concerns about an apparent increased spontaneous abortion risk in a payroll office environment. Concern in this office centered on the use of video display terminals (VDTs), which have been investigated as a potential cause of adverse reproductive outcomes among women. In this investigation, magnetic field sources were evaluated using a hand-held survey meter. Emdex datalogging dosimeters were also used to determine full shift personal exposures for 15 women working in the payroll area. On average, the exposures of workers to ELF magnetic fields in the payroll office area ranged from 1.0 to 6.5 mG with a mean of 3.2 +/- 1.5 mG. The results of this study indicate that many sources of ELF magnetic fields, including printers, photocopiers, and the electrical distribution system, can contribute to a worker's exposure in an office environment.

Computer Terminals

[Effects of goal setting and real-time feedback on performance and time estimation during VDT operation].

The problem of serious occupational fatigue of software operators has come up for discussion. Along with the outcome of a survey showing that their working hours are longer than those of other types of workers, with the former reporting for duty unconsciously early in the morning, it is pointed out that their time estimation and crookedness of time cognition are reduced. As a result of the survey, it was also found that in visual display terminal task, the work is carried on while receiving real-time feedback, and those engaged in development work, set their goal to complete a specific amount of work within a specific time-limit. Thus, in order to examine the effects of these two factors on these workers' performance and their subjective time estimation, 76 subjects (undergraduate students) were asked to engage in task of six terms. The results indicated that the group with its goal set and real-time feedback given had higher performance and motivation for task, and showed more time reduction than did other groups to a significant extent. It is noteworthy that it was proved that the subjects were not conscious of this time reduction.

Adult

Musculoskeletal disorders among visual display terminal workers: individual, ergonomic, and work organizational factors.

A number of individual, ergonomic, and organizational factors of presumed importance for the occurrence of musculoskeletal disorders were investigated in a group of 260 visual display terminal (VDT) workers. The cross-sectional study utilized medical and workplace investigations as well as questionnaires. The results were subjected to a multivariate analysis in order to find the major factors associated with various upper-body muscular problems. Several such factors were identified for each investigated type of musculoskeletal problem. Some were related to the individual: age, gender, woman with children at home, use of spectacles, smoking, stomach-related stress reactions, and negative affectivity. Organizational variables of importance were opportunities for flexible rest breaks, extreme peer contacts, task flexibility, and overtime. Identified ergonomic variables were static work posture, hand position, use of lower arm support, repeated work movements, and keyboard or VDT vertical position.

Adult

Epidemiological studies of work with video display terminals and adverse pregnancy outcomes (1984-1992).

Many epidemiological studies have investigated the claim that work with video display terminals (VDT) is a risk factor during pregnancy. Results have been inconsistent, although in the majority of cases the hypothesis was not supported. Exposure assessment has been very poor and the statistical power of the studies generally low. Overall, the studies indicate that VDT operators are not at greater risk than the general population, because very low frequency (VLF) magnetic fields do not appear to be a risk factor and extremely low frequency (ELF) magnetic field exposure is not significantly greater than that experienced in other occupational and residential environments. However, since some studies lend support to the hypothesis that ELF magnetic fields may be a risk factor for pregnancy outcome, studies of subjects exposed to higher than average ELF fields are justified.

Abortion, Spontaneous

Spontaneous abortion among women using video display terminals.

This case-base study with a source population of 214 108 commercial and clerical workers investigated the risk of adverse pregnancy outcome among women working with a video display terminal (VDT) in Denmark. A subpopulation was obtained by register linkage between a trade union membership file, the Medical Birth Register, and the National Register of In-Patients. In two years 24,352 pregnancy outcomes were registered, 2248 spontaneous abortions were recorded, and a base sample of 2252 pregnancies was randomly selected. Data on VDT use, job stress, ergonomic factors, and life-style factors were collected with questionnaires sent to 6212 women and 426 employers. There was no increased risk of medically verified spontaneous abortion among women with VDT use. The relative risk for women exposed to any degree of use was 0.94 (95% confidence interval 0.77-1.14). Ergonomic work load and job stress were not confounders.

Abortion, Spontaneous

[Mean-term variations of visual function of video display terminal operators: observations on 70 cases].

The aim of the study was to evaluate medium-term variations of visual functions in VDT operators and their possible relationship to VDT exposure. The clinical records of 70 VDT operators attending our outpatient service for periodical ergophthalmological evaluation were reviewed in order to evaluate the variation of some visual parameters after a two-years follow-up. These included refraction, phorias, fusional convergence and divergence, stereopsis. The group did not include subjects affected by hyperopia, large ametropias, or binocular vision disturbances and was divided into two subgroups: low exposure group (n = 20; < 4 hours/day) and high exposure group (n = 50; exposure > 4 hours/day). Asthenopia was frequent in both groups. Variation of refraction and binocular vision parameters were absent or rather limited in both exposure groups. This seems to indicate that in subjects without significant ophthalmological problems the risk of permanent functional damage is very low at medium-term.

Adult