Work Content and Eye Discomfort in VDT Work Gunnar Aronsson, Anneli Strömberg, 1-13 Protection Against Dust by Respirators R. C. Brown, 14-28 Dimensions of Job Control in Computerized and Traditional Office Work and Its Health Effects Maria Widerszal-Bazyl, Dorota Żołnierczyk, 29-41 Repetitive Strain in Nonrepetitive Work: A Case Study Céline Chatigny, Ana Maria Seifert, Karen Messing, 42-51 Development of Micropore Mufflers Li Peizi, Dai Genhua, Li Lu, 52-63 Predictive Models of Lumbar Loadings When Handling Boxes Gilmen Smyth, Micheline Gagnon, Roch Roy, 64-77 Musculoskeletal Symptoms in Two Plants in the Electrical Sector Marie St-Vincent, D. Chicoine, 78-90

Work Content and Eye Discomfort in VDT Work
Gunnar Aronsson, Anneli Strömberg, 1-13

A questionnaire study of Swedish public employees with frequent and different types of VDT work (n=2,025) was conducted. Eight different kinds of eye discomfort were examined, and an additive index was constructed. Eye discomfort was statistically related to aspects of work organization. The highest levels of discomfort were reported by computer-aided design (CAD), data entry, and word processing groups; groups with mixed VDT tasks displayed the lowest level of symptoms. Time spent at a VDT, low degree of work control, time pressure and high pace of work were all associated with relatively high levels of eye discomfort. There was significant interaction between experience of stress and time spent at a VDT with respect to both the eye discomfort index and three specific symptoms (itching, gritty feeling and dryness). Whereas dryness, smarting and itching of the eyes seem most strongly related to work conditions; redness and watery eyes seem most weakly related.

Protection Against Dust by Respirators
Richard C. Brown, 14-28

The article is a brief review of the mechanism of action of fibrous filters and of the performance of respirators; it neglects many of the complications discussed in longer and more detailed articles. An expression is given for the pressure drop across a filter in terms of fibre diameter and filtration velocity. The particle capture mechanisms of interception and diffusional deposition are introduced and the way in which filtration efficiency varies with particle size is discussed. Filters with fibres of small diameter are shown to be the most efficient, but their use can cause problems. Electrically charged materials are widely used in respirators because of their high efficiency and low pressure drop.
Types of material, their means of charging and their method of action are described. An account is given of respirator leakage, the protection factor, and of the way that these may vary in a period of use. The leakage of air and particles through face seal leaks and leaky valves is discussed. The frequent discrepancy in the protection given by respirators in the workplace, on the one hand, and that suggested by laboratory measurements, on the other, is reviewed, and the article ends with an account of the combined effect of aerosol penetration through a filter and through a leak.

Dimensions of Job Control in Computerized and Traditional Office Work and Its Health Effects
Maria Widerszal-Bazyl, Dorota Żołnierczyk, 29-41

This study investigates whether a consistent relationship exists between computerization and job control. It also examines the role of job control as a predictor of stress symptoms typical for data entry and word processing (VDU) work. Two groups of VDU users and two comparable non-VDU-user groups took part in this study. A special questionnaire made it possible to assess global job control and four indexes of control related to specific aspects of work (control over choice of tasks and methods, control over time frame, control related to one's skill, and control related to participation in the decision making process). Results did not show an unequivocal relation between computerization and the latitude of control. The latitude of control depends on the task performed and the aspect of control we are considering. Regression analyses showed that global control is a good predictor of job satisfaction, some mood disturbances, and visual complaints. The other aspects of control are related in a variety of ways to stress symptoms. The role of a Type A behavior pattern in the relationship between job control and stress symptoms varies depending on which aspect of control is being considered. It was concluded that because of the high functional differences between various aspects of control, it is better to avoid using the concept of global control and, when possible, apply specific indexes of control.

Repetitive Strain in Nonrepetitive Work: A Case Study
Céline Chatigny, Ana Maria Seifert, Karen Messing, 42-51

In a Québec factory, a woman in a nontraditional job suffered from epicondylitis whereas her male coworkers were unaffected. A study was undertaken in order to enumerate the operations at risk for epicondylitis. Workers were interviewed in order to identify difficult operations and systematic observations were done over 4 workdays. Although tasks were extremely varied, certain movements at risk for epicondylitis were repeated many times. Fifty-three valves were turned against resistance as part of this job, and one valve requiring a particularly difficult movement was turned 20 times in one day. There were at least 61 operations at risk for epicondylitis per day over a 4-day period. Strain on the elbow joint was particularly intense for the woman worker because the design of the workplace gave an advantage to taller workers with larger hands. Although this case study does not permit us to conclude that the worker's epicondylitis was due to her job, it enables us to suggest that it would be wise to adapt the dimensions of relevant equipment and worksites to a wider range of potential worker sizes. We also raise some questions about the definition of repetitive strain in epidemiological studies. We suggest that it may be necessary to consider not only the cycle time but also the total of forces exerted on a joint in order to study workplace injuries to the musculoskeletal system.

Development of Micropore Mufflers
Li Peizi, Dai Genhua, Li Lu, 52-63

Research on micropore mufflers was started in the middle of the 1970s. In this paper we have summarized and systematized what has been done in the past 20 years. Some expressions, derivations and calculation curves have been formally modified to make them easier to understand and apply. Some new considerations have been added. The main purpose of this article is to introduce the fundamentals, theories and calculations, that are useful for the design of a micropore muffler. Therefore, we have not included any experiments. Direct and indirect experimental proofs can be found in the given relevant references. Micropore mufflers are grouped into two classes, simple micropore mufflers and expansion micropore mufflers. The latter have additional noise reduction due to flow expansion. Noise reduction and flow are two important aspects that have been discussed in detail.

Predictive Models of Lumbar Loadings When Handling Boxes
Gilmen Smyth, Micheline Gagnon, Roch Roy, 64-77

Back problems resulting from the compression forces on the intervertebral disks during manual material-handling tasks are an important problem affecting workers in various industries. The quantification of these forces using intradiscal pressure or biomechanical modeling is complex, time-consuming, or costly, and these methods cannot be readily used in the workplace to estimate loadings on the lower back. The objective of this study was to develop a predictive model that would allow the estimation of lumbar loadings for lifting and lowering boxes using easily measured anthropometric variables and variables related to the task. A dynamic and planar segmental model and a model of internal forces at L5/S1 were used to determine the compression forces on the lower back. Two predictive models, a field model and a laboratory model, were developed to estimate the compression forces when lifting or lowering 3.3 kg to 22.0 kg boxes between heights of 15 cm and 185 cm. Both models were validated by an examination of the residuals. Their predictive performance was also compared, with the laboratory model offering a slightly better prediction than the field model. Thus, these equations represent a practical tool for a better planning of handling tasks in the working environment with the purpose of reducing the back injuries of workers.

Musculoskeletal Symptoms in Two Plants in the Electrical Sector
Marie St-Vincent, Denis Chicoine, 78-90

The study consisted of describing, using a questionnaire, the musculoskeletal symptoms in two industries in the electrical sector. The questionnaire was distributed to more than 600 workers in the two industries. The questionnaire described four types of variables: usual population data (age, gender, experience, etc.), certain work variables, the regions of the body affected in the past 12 months and in the past 7 days, and the severity of the symptoms. Ten variables were used to provide a symptom severity index. In the two plants, the women reported more frequent and more serious problems than the men and the least experienced workers were the most affected. In Plant 1, the questionnaire pinpointed two work sectors, whereas in Plant 2, the problems were found not to be concentrated in a few sectors, but distributed among different jobs throughout the entire plant.