Ernst Kiesswetter

Re-entrainment of body temperature in field studies of shiftwork

SummaryOral temperature readings were taken from six groups of shift-workers (n = 133). The measurements covered a total of 387 days and included readings on a day off and on days of the 1st, 2nd, 4th, 5th and 7th nightshift. The shiftworkers were asked to record oral temperature every 2 h, at work and at leisure, using special thermometers (1°C equals 4 cm). Some of them also interrupted their sleep for additional measurements.On the first day of the night shift the normal circadian rhythm of body temperature was virtually unchanged in most of the groups. However in two groups with a higher physical load during nightwork, an increased temperature was observed during the night (“masking effect”). There were no significant differences between the temperature rhythms in experienced (≥ 15 years of shiftwork) and inexperienced shiftworkers (≤ 1 year of shiftwork) within the first nightshift. During the period of consecutive nightshifts no clear re-entrainment of body temperature was observed. Re-entrainment to nightwork appears to be slower in field studies than in experimental shiftwork studies, which might be explained by the influence of unshifted social “Zeitgebers” in real life.

Time-budget studies of policemen in weekly or swiftly rotating shift systems.

For 8 days 120 policemen kept special diaries including working time, travelling to and from work, leisure time and sleeping time. By analysing the data of leisure and sleep in relation to the time of day and the type of shift it is possible to find out critical points within a shift system. The mean duration of sleep was reduced before morning shifts, between night shifts and after a morning shift that was followed by a night shift on the same day. The leisure time was limited in connection with afternoon shifts and between the combined morning and night shift. It is recommended not to have double shifts on one day. Rapidly rotated shift systems had more advantages referring to the total amount of night sleep than weekly rotated shift systems. The backward rotation of shifts was unfavourable because of the short time off between the last afternoon shift and the first morning shift. Furthermore, short nightwork periods and a start of the morning shift which is not too early seem to be preferable.

Effects of sleep loss, time of day, and extended mental work on implicit and explicit learning of sequences

Tacit knowledge is part of many professional skills and can be studied experimentally with implicit-learning paradigms. The authors explored the effects of 2 different stressors, loss of sleep and mental fatigue, on implicit learning in a serial-response time (RT) task. In the 1st experiment, 1 night of sleep deprivation was shown to impair implicit but not explicit sequence learning. In the 2nd experiment, no impairment of both types of sequence learning was found after 1.5 hr of mental work. Serial-RT performance, in contrast, suffered from both stressors. These findings suggest that sleep deprivation induces specific risks for automatic, skill-based behavior that are not present in consciously controlled performance.

Physiological and psychological approaches to chemosensory effects of solvents

Workplace related standard settings for solvents are based in a remarkable extent on information about sensory irritations. However, data from controlled human exposure studies are seldom available. Therefore, the aim of this study was to present the association of self-reported symptoms and physiological processes leading to sensory irritations. Three series of laboratory experiments each with 24 young male subjects were performed. Ethyl benzene (EB), 2-butanone (methyl ethyl ketone or MEK), isopropyl alcohol (IPA), 1-octanol (OCT), and 2-ethylhexanol (EHEX) were investigated in low and high concentrations. Ratings for sensory irritations (eyes and nose), olfactory symptoms, and annoyance were assessed repeatedly before, during and after the 4-h-exposures. The anterior active rhinomanometry (AAR) was employed measuring the nasal flow. The nasal lavage was used for the analysis of the neuropeptide substance P as indicator of nasal chemosensory irritations. Goodness-of-fit was calculated for non-linear regression analyses by fitting the sine function on the data of the ratings given during the 4-h-exposure. In general, ratings for annoyance and odor symptoms were fitted on a higher level than those for sensory irritations. However, a high fit could be shown for nasal irritations due to EHEX. In these experiments, a significant reduction of the nasal flow and a significant increase of substance P could be proved.

A change from weekly to quicker shift rotations: a field study of discontinuous three-shift workers

Abstract 52 male employees in the food processing industry, who were working on a weekly, backward rotating, and discontinuous shift system, were studied. An experimental group (n= 31) consisting of four subgroups changed their shift systems while a control group (n= 21) consisting of two subgroups did not. The new shift systems were rapidly rotating mainly in the forward direction. Before, and half a year after the change, two questionnaire studies were conducted. In the experimental group, sleep difficulties during days with night shifts, and difficulties with continuation training in connection with afternoon shifts, were reduced on the new shift systems. Sleep durations, as well as gastrointestinal and neurovegetative symptoms, were not affected by the change of shift systems. Although 18 of 31 subjects earned less money on the new shift system (because of a reduction in overtime), 83.9% of the experimental group voted in favour of the new shift systems.

Eye blinks as indicator for sensory irritation during constant and peak exposures to 2-ethylhexanol.

Two experiments were performed to re-evaluate the sensory irritating properties of 2-ethylhexanol in relation to dose and time and to examine the usability of electromyographic eye blink recordings as indicator of sensory irritation. Mean exposure levels of 1.5, 10 and 20ppm were realized in experimental models simulating either constant or variable 4h exposure. Each study was carried out with two subject samples, healthy young men with self-reported multiple chemical sensitivity (sMCS) and age matched controls. Although 2-ethylhexanol exposure was below the occupational threshold limit value of 50ppm, the study revealed strong dose-response relationships between airborne solvent concentrations and blink rates. During 40ppm peak exposures the blink rate increased threefold. In the course of 4h, exposure blink rates increased significantly showing no adaptation. Subjects with sMCS revealed, with one exception at start of exposure, no significantly higher blink rates than controls. The results indicate that the irritative potential of 2-ethylhexanol is higher than commonly expected. In both exposure scenarios with either constant or peak exposures, electromyographic eye blink recordings were an appropriate method for the examination of acute sensory irritations in time.

An integrative approach considering acute symptoms and intensity ratings of chemosensory sensations during experimental exposures.

Even at low concentrations airborne chemicals can excite olfactory and trigeminal receptors and inform the organism about the presence of airborne chemicals. Acutely, malodors or sensory irritations might trigger symptoms (e.g., bad air quality, eye irritations) and in the long-run functional impairment of chemoreception might occur. In humans, knowledge about short-term adaptational processes and effects of exposure peaks on these systems is limited. Therefore, two different experiments with human volunteers were conducted. In experiment A exposures (4h) with fluctuating concentrations of 2-ethylhexanol (1.5, 10, 20ppm C(TWA)) were investigated, experiment B used similar but constant vapor concentrations. Olfactory- and trigeminal-mediated symptoms and intensities of odor, eye, and nasal irritations were recorded. All measures showed a dose-dependent response and peak exposure effects. In the course of the 4h exposures solely olfactory symptoms decreased. Nasal irritations remained nearly unchanged across the 4h, eye irritations slightly increased. Inter-individual differences related to the personality trait of self-reported chemical sensitivity had only minor effects on chemosensory symptoms in experiment B and no effect on intensity ratings in both experiments. Chemosensory effects seem to be amplified by exposure peaks and less adaptive than assumed.

Sensory and pulmonary effects of acute exposure to sulfur dioxide (SO2)

BACKGROUND Exposure to sulfur dioxide (SO(2)) affects large populations worldwide. Pulmonary effects have been reported at concentrations relevant in the general (<0.5 ppm) and working environment (>0.5 ppm). SO(2) is an irritant but the existing studies often emphasize only pulmonary effects and no clear dose-response relationship has yet been described. OBJECTIVES Using a multi-level, multi-method approach, odor annoyance, sensory irritation and pulmonary effects of SO(2) were to be investigated in an experimental exposure study. METHODS Eye blink frequency, rhinomanometry, spirometry and symptom ratings of acute health effects were assessed before, during, and after the exposures. Each session lasted 4h and concentrations of 0.5, 1, and 2 ppm were investigated and compared to a control condition using clean air. Sixteen human volunteers (8 females/8 males) participated and during exposure light physical exercise was simulated with bicycle ergometry. RESULTS Eye blink frequency, nasal airflow, and lung function were not affected by the acute SO(2) exposure investigated. These physiological responses to moderate SO(2) exposures were not significantly affected by gender. Regarding subjectively measured chemosensory sensations, only odor annoyance ratings increased in a dose-dependent manner, but the average magnitudes were labeled weak to moderate. CONCLUSIONS In healthy volunteers, without hyperresponsiveness to SO(2), no dose-dependent effects of acute SO(2) exposures up to 2 ppm could be measured. Due to olfactory perceptions subjects were aware of the different SO(2) exposures but the associated annoyance was relatively low.

Neurobehavioral effects during exposures to propionic acid--an indicator of chemosensory distraction?

The chemosensory effects of propionic acid (PA) in humans have not been conclusively studied and there is no established occupational exposure limit (OEL) in Germany. In addition to sensory irritation caused by PA, it was hypothesized that the annoying odor of PA might interfere with the performance results. There were 23 consenting healthy participants (12 female, 11 male) in the group studied. They were exposed for 4 h to PA in concentrations of 0.3, 5 and 10 ppm in a cross-over design. During these exposures, performance was recorded with four cognitive tests measuring response-inhibition, working memory, set-shifting, and divided attention. Odor annoyance, other chemosensory sensations, and acute symptoms were assessed before, during, and after exposure with standardized rating scales. Moderate odor annoyance and weak sensory irritation were reported during 5 and 10 ppm exposure conditions. The different levels of exposure to PA had no impact upon the results of three out of the four behavioral tests. The difficulties of the task were reflected in the results. However in the fourth, which was the response-inhibition task, there was significant increase in the error rates which corresponded to the exposure levels. Results from previous experiments suggested high odor annoyance at the investigated concentrations. Our findings showed that odor annoyance and reported sensory irritations were low. In conclusion, the hypothesis of a distractive effect due to the malodor of PA could not be confirmed. Only in concentrations as high as 10 ppm acute PA exposure affected the response accuracy of one of the four neurobehavioral task. For other more annoying substances, a neurobehavioral effect influenced by an indirect mechanism of resources competition is still conceivable.

Breathing and Heart Rate during Experimental Solvent Exposure of Young Adults with Self-Reported Multiple Chemical Sensitivity (sMCS)

This paper deals with the assumption that young adults with self-reported multiple chemical sensitivity (sMCS) show a heightened sensitivity of autonomic functions during experimental solvent exposure. Male sMCS-subjects were selected (out of n=274) on the base of a German questionnaire on chemical and environmental sensitivity (CGES). Two independent experiments were carried out, each with 12 sMCS-subjects and 12 age-matched control-subjects. In experiment I two concentrations of the solvents ethyl benzene (10 and 98 ppm) and 2-butanone (10 and 189 ppm) were used. Experiment II investigated 2-propanol (35 and 190 ppm) and 1-octanol (0.1 and 6.4 ppm). The low concentrations correspond nearly to the olfactory thresholds while the high concentrations correspond to the German occupational threshold limit values (MAC). The exposure duration under each condition was 4h. The sequence of the four exposure conditions was random including intervals of at least 2 days without exposure. During the exposure physiological changes of breathing rate and heart rate were recorded. Two 30 min intervals with a sedentary position of the subjects at the beginning and end of exposure were chosen for analyses. Neither in experiment I nor in experiment II significant specific reactions to the type or level of the exposures were found. The autonomic functions in both experiments revealed alterations within the exposure sessions. The heart rate in experiment II and the breathing rate in both experiments decreased significantly during the analyzed 30 min intervals. Furthermore, in both experiments the heart rates decreased significantly from beginning to end of exposure. Only in experiment I the mean breathing rate of sMCS-subjects was generally higher compared to the control-subjects. Regarding the assumption of a heightened sensitivity of sMCS-subjects the two experiments yielded controversial results. Thus, the hypothesis of stronger responses of autonomic functions of sMCS-subjects provoked by various exposure scenarios remains open.