The Effects of Hearing Protectors on Auditory Localization: Evidence From Audio-Visual Target Acquisition Robert S. Bolia, Richard L. McKinley, 309-319 Application of a Fibrous Electrostatic Filter for Treatment of Diesel Exhaust Tomasz Ciach, Tomasz R. Sosnowski, 321-333 Body Heat Balance of a Man with Deficient Sweat Rate Subjected to Physical Work in a Hot Environment Krzysztof Sołtyński, Maria Konarska, 335-345 Evaluation of Low Back Pain Risks in a Beef Skinning Operation Biman Das, Arijit K. Sengupta, 347-361 Some Problems Associated With Shift Work Krzysztof Kwarecki, Jim Waterhouse, 363-364 Working and Health Conditions of Italian Air Traffic Controllers Giovanni Costa, 365-382 Circadian Rhythm of Heart Rate, Urinary Cortisol Excretion, and Sleep in Civil Air Traffic Controllers Krystyna Zużewicz, Krzysztof Kwarecki, Jim Waterhouse, 383-392 Can Nurses Be Employed in 12-Hour Shift Systems? Teresa Makowiec-Dąbrowska, Patrycja Krawczyk-Adamus, Elżbieta Sprusińska, Zbigniew W. Jóźwiak, 393-403 Internal and External Factors Influencing Time-Related Injury Risk in Continuous Shift Work Andrzej Ogiński, Halszka Ogińska, Janusz Pokorski, Wacław Kmita, Roman Goździela, 405-421

Reports on International Events, 423-426

The Effects of Hearing Protectors on Auditory Localization: Evidence From Audio-Visual Target Acquisition
Robert S. Bolia, Richard L. McKinley

Response times (RT) in an audio-visual target acquisition task were collected from 3 participants while wearing either circumaural earmuffs, foam earplugs, or no hearing protection. Analyses revealed that participants took significantly longer to locate and identify an audio-visual target in both hearing protector conditions than they did in the unoccluded condition, suggesting a disturbance of the cues used by listeners to localize sounds in space. RTs were significantly faster in both hearing protector conditions than in a non-audio control condition, indicating that auditory localization was not completely disrupted. Results are discussed in terms of safety issues involved with wearing hearing protectors in an occupational environment.

Application of a Fibrous Electrostatic Filter for Treatment of Diesel Exhaust
Tomasz Ciach, Tomasz R. Sosnowski

The paper presents results of investigations of a novel method for diesel exhaust filtration in a fibrous filter supplemented by the external electrostatic field (FEF), which may be used to eliminate the occupational hazard near sources of diesel emission. The reported research follows the preliminary basic study of soot removal in such systems (Ciach, Sosnowski, & Podgórski, 1995), and is focused on the construction and testing of a prototype technical-scale FEF device. The results suggest a strong relation between applied voltage and filtration efficiency of the system and demonstrate the influence of aerosol precharging on the efficiency, which can be more than 95%.

Body Heat Balance of a Man with Deficient Sweat Rate Subjected to Physical Work in a Hot Environment
Krzysztof Sołtyński, Maria Konarska

The dynamics of physiological stress and thermal balance were investigated in men subjected to endogenous and exogenous heat loads. The study was conducted using the thermometric method. Substantial differences in the dynamics of the tested parameters and their quantitative characteristics were observed in 1 out of 8 participants. In this article, the observed differences are rationalized in terms of the deficient sweat rate mechanism. It is pointed out that it is indispensable to address these cases in work safety regulations.

Evaluation of Low Back Pain Risks in a Beef Skinning Operation
Biman Das, Arijit K. Sengupta

The low back pain risks in a beef skinning operation at a high stand kill floor workstation was evaluated. The increases in compressive forces at lower back (L5/S1) between normal slump (back angle 25°, measured in the sagittal plane) and severe (45°) and between normal slump and very severe (70°) bent back postures were 387 N or 28% and 616 N or 45%, respectively. The high spine load coupled with high level of repetition can have a high probability of fatigue failure in the spine structural members. Non-neutral back posture for a large portion of the total work time can be a low back pain risk factor. The videotape analysis showed that the times involved during the task performance for the bent back (more than 25°) and severe bent back (more than 45°) were 48.4 and 33.5% of the total cycle time, respectively. The upper limit from OWAS (Ovako Working Posture Analysis System) for bent back posture is 30% of the total cycle time. The bent and twisted back posture (both more than 25°) time was 10.4% compared to OWAS limit of 5%. This indicated that actions are needed in the near future to alleviate the risk of low back pain. Ergonomics redesign of the workstation was recommended for the operation.

Some Problems Associated With Shift Work
Krzysztof Kwarecki, Jim Waterhouse

It is widely accepted that shift work is a necessary concomitant of a modern society, and estimates indicate that about 20% of the workforce is required to work at night and sleep during the daytime.
The fact that night work is common has not removed some of the problems that are associated with it (Waterhouse, Folkard, & Minors, 1992). On the one hand, the night workers themselves have problems, related not only to difficulties with managing to stay awake at night and to sleep during the day but also, in the longer term, with health problems, at least in a susceptible fraction of the workforce; on the other hand, the employers have concerns because the quality and quantity of work performed on the night shift can be lower than on the day shifts. Moreover, if there is a greater incidence of errors and accidents when work is done at night, then this might have repercussions that extend far beyond the workplace and its immediate environs.
The present articles cover many of these aspects of shift work.
That by Costa (page 365) deals with the health of air-traffic controllers in a large study performed in Italy. There was a higher incidence of several disorders, notably those involving the digestive, neuropsychic, and cardiovascular systems but, in general, the health of the sample seemed to be quite good in comparison with the working population as a whole. Costa attributes this to the high motivation of the participants, to the design of the shift system itself, and to the frequent medical examinations that were given to the workforce.
Zużewicz, Kwarecki, and Waterhouse (page 383) also consider air-traffic controllers, but this time the study took place in Poland and the main areas of investigation were physiological and biochemical estimates of stress, and sleep hygiene. Again, the amount of stress seemed not to be particularly high but, as in Costa's study, it appeared to be proportional to the age and experience of the participants. Moreover, the increasing use of a daytime nap in older and more experienced subjects can be interpreted as a sign of increasing stress, of the development of coping mechanisms with age and experience, or of both.
Ogiński, Ogińska, Pokorski, Kmita, and Gozdziela (page 405) concentrate on the frequency of accidents in a steel mill in Cracow, Poland, relating it to several factors including the season, climate, time of day, time on shift, and day of shift. Serious injuries appeared to be more frequent on the night shift, and injuries in general more frequent towards the end of a shift, with increasing number of days on the shift, and in the summer rather than the winter. In discussing their results, the authors stress the effect of factors that promote fatigue and the value of adequate sleep, but they also point out the importance of social factors, of the work environment, of the relationships between the individual, management, and colleagues, and of the type of shift system.
The importance of the shift system has been the subject of several recent studies, including the problem of 12- versus 8-hr shifts. The advantage of 12-hr shifts is that the individual has to go to work less frequently than if 8-hr shifts are worked; the potential problem is the possible effect of increased time on shift upon performance and stress. Several aspects of this are considered by Makowiec-Dąbrowska, Krawczyk-Adamus, Sprusińska, and Józwiak (page 393). They studied sleep, lifestyle, and physical and mental stresses in groups of nurses from several hospital departments who were working either 8- or 12-hr shifts. Many of the measurements were self-assessments, but there were also estimates made by observers. The study concluded that the 12-hr shifts were associated with a greater mental load but a lesser physical load than the 8-hr shifts. Also, those working the 12-hr shifts felt more tired at the end of their work, but they were able to get more sleep and undertake more active pursuits during the extra free days. The authors conclude that there is no reason why nurses should not work 12-hr shifts.
Putting all these results together, it seems that, if the workforce is satisfied with the shift system, the conditions at work and at home, and if there are regular medical examinations, then many of the problems associated with night work are decreased. Even so, biological factors continue to exert an effect upon performance and accidents, and it remains unknown whether a satisfied workforce will remain healthier in the longer term.
REFERENCE
Waterhouse, J., Folkard, S., & Minors, D. (1992). Shiftwork, health and safety. An overview of the scientific literature 1978-1990. [Health and Safety Executive Contract Research Report No. 31]. London, UK: Her Majesty's Stationery Office.

Working and Health Conditions of Italian Air Traffic Controllers
Giovanni Costa

The paper summarises some studies carried out in recent years on Italian air traffic controllers. Work stress appeared related mainly to mental charge, aggravated by time pressure and high responsibility. Shiftwork was not considered highly stressful, thanks to the good shift schedules adopted. The disorders most frequently complained of had a prevalent psychosomatic component, concerning the digestive, neuropsychic, and cardiovascular systems. However, their prevalence was lower than, or similar to, that recorded in general population. The controllers engaged in regional centres showed slightly worse health conditions than those engaged in airport towers; the same was found in the radar controllers compared to those working in non-radar positions.

Circadian Rhythm of Heart Rate, Urinary Cortisol Excretion, and Sleep in Civil Air Traffic Controllers
Krystyna Zużewicz, Krzysztof Kwarecki, Jim Waterhouse

The examination of Air Traffic Controllers (ATCs) from the Warsaw Airport (Poland) included 24-hr ECG monitoring. The participants were 10 civil ATCs, 9 males and 1 woman. The study was carried out on a group of 19 ATCs during their duty periods, 14 of them working 12-hr shifts and 5 performing 24-hr duties. The participants collected urine every 4 hrs, and cortisol concentration was determined. Further, the survey included the quality and duration of sleep, and subjective fatigue in the 62 participants.
In ATCs, shift work modifies natural rhythms of the circulatory system and decreases the ability for intensified mental work at night. In consequence ATCs experience frequent sleep disorders.

Can Nurses Be Employed in 12-Hour Shift Systems?
Teresa Makowiec-Dąbrowska, Patrycja Krawczyk-Adamus, Elżbieta Sprusińska, Zbigniew W. Jóźwiak

Nurses are often obliged to work in a 12-hr shift work system. We have decided to check whether such a working system constitutes an excessive load for nurses. On the basis of a questionnaire survey among nurses working in an 8-hr daytime shift system (169 nurses) and in a 12-hr shift (536 nurses), the amount of physical workload, work stress, and after-work activities were compared. Data analysis has shown that a 12-hr shift system is characterized by less significant physical workload but greater mental load. The nurses working in a 2-shift system were more tired after work, but they could spend more time on leisure activities and do housework. The data suggest that there are no significant contraindications for nurses to work in a 2-shift system.

Internal and External Factors Influencing Time-Related Injury Risk in Continuous Shift Work
Andrzej Ogiński, Halszka Ogińska, Janusz Pokorski, Wacław Kmita, Roman Goździela

Time-related accident risk in shift work may be attributed to internal factors, such as fatigue, level of performance, sleep propensity, and to some external factors, like shift system, physical and social environment. Six hundred and sixty-eight events in the metallurgical industry have been analysed in terms of time of day, time on task, consecutive day of the shift block, day of the week, and season.
The injury rate was similar on all shifts but more severe accidents happened in the nighttime. Somewhat more injuries occurred in the second half of the shift, in the second part of a shift block, and in summer compared with winter. There were fewer injuries at weekends.