Showing papers by "Barbara Griefahn published in 2002"

Sleep Disturbances Related to Environmental Noise.

Abstract: The permanently open auditory channel and the ability of the brain to process incoming acoustical stimuli even while asleep and to respond adequately is the essential precondition for noise-induced sleep disturbances which are regarded as the most deleterious effects of noise. In the past, research was mainly focused on the detection and description of the various effects of noise, on the influence of personal and environmental factors, on the determination of dose ­response relations and the definition of critical noise loads, above which noise becomes intolerable. These limits are, however, as yet only tentative or applicable for a very few situations and need to be verified or revised. The present paper is focused on the priorities for future research. These are in particular 1) the causal linkage between environmental noise, primary and secondary effects on the one hand and the hypothesized contribution to multifactorial chronic diseases, to chronic annoyance, and to permanent behavioral alterations on the other hand, 2) the identification of the causes for the great discrepancies between the small effects determined in the field and the large responses recorded in the laboratory, 3) temporal aspects such as sleep at unusual times (day sleep after nightshifts), definition of night-time and day-time, 4) the significance of the shoulder hours for subsequent sleep, 5) the individual vulnerability, 6) the accumulation of data from different studies.

Assessment of the risk of heat disorders encountered during work in hot conditions

Abstract: Objective: To co-ordinate the work of the main European research teams in the field of thermal factors in order to develop and improve significantly the methods presently available for assessing the risks of heat disorders encountered during work in hot conditions. Method: Each item from the required sweat rate model was reviewed on the basis of the most recent literature. A database with 1,113 laboratory and field experiments, covering the whole range of hot working conditions, was assembled and used for the validation. Results: Influence of clothing ensemble on heat exchange: methods and formulas were developed that take into account the dynamic effects associated with forced convection and the pumping effect associated with body movements and exercise. Prediction of the average skin temperature: the model used in the required sweat rate standard ISO 7933 was extended to cover more severe conditions with high radiation and high humidity and different clothing and take into account the rectal temperature for the prediction of the skin temperature. Criteria for estimating acceptable exposure times in hot work environments: criteria were reviewed and updated concerning the maximum increase in core temperature and the acceptable water loss, for acclimatised and non-acclimatised subjects. These limits are intended to protect 95% of the population. Measuring strategy: a strategy was developed to assess the risks in any working situation with varying conditions of climate, metabolic rate or clothing. A detailed methodology was developed in three stages: an "observation" method for the recognition of the conditions that might lead to thermal stress; an "analysis" method for evaluating the problem and optimising the solutions; and an "expert" method for in-depth analysis of the working situation when needed. Validation: the different results were used to prepare a revision of the interpretation procedure proposed in the ISO standard 7933. We validated the modified approaches using the database. This involved the whole range of conditions for which the model was extended, namely conditions with high and low radiation, humidity and air velocity as well as fluctuating conditions. Based on these results, the predicted heat strain model was developed: it is presently proposed as an ISO and CEN standard.

Melatonin synthesis: a possible indicator of intolerance to shiftwork.

Abstract: Hypothesis Melatonin synthesis, which is directly controlled by the central circadian pacemaker indicates the circadian phase better than rectal temperature. Methods Thirty four men (16-32 years, 7 morning, 13 neither, 14 evening types) performed a constant routine (24-26-hr bedrest, <30 lux, 18-20degreesC, hourly isocaloric diet). Salivary melatonin level was determined hourly and rectal temperature was continuously recorded. Results The nadir of rectal temperature occurred 1.5 hr (P = 0.017), the onset of melatonin synthesis 3 hr earlier (P < 0.0001) in morning than in evening types. Morningness was not related to the quantitative but significantly to the temporal parameters, closer to those of melatonin than of rectal temperature. Conclusions The melatonin onset is a more reliable indicator of the diurnal type than the nadir of rectal temperature. As morningness has been associated with intolerance to shiftwork, melatonin profiling provides a suitable basis for the establishment of directed preventive measures. (C) 2002 Wiley-Liss, Inc.

Evaluation of draught in the workplace.

Abstract: During 826, 1-h sessions 107 participants (33 women, 74 men, 18-51 years of age) were exposed to defined draughts where air velocity (0.1 ≤ V a ≤ 0.4 m s -1), turbulence intensity ( 70%), draught direction (horizontal, vertical, diagonal), air temperature (11 ≤ t a ≤ 23°C), and metabolic rate (≈ 60 ≤ M ≤ 156 W m -2) were varied but kept constant during single sessions. Perception and evaluation (annoyance due to draught and local cold) were registered using a list of prescribed body parts. Annoyance due to draught increased with the increase in mean air velocity and in turbulence intensity, as well as with the decrease in air temperature and in metabolic rate. The direction of air flow had no influence. As these responses were neither sufficiently predicted by the draught-rating model proposed in ISO 7730 (1994), nor by its extension developed by Toftum (1994a), the latter was modified according to the data registered in this paper. Using the modified model the accordingly predicted percentage ...

Night-time Noise Annoyance: State of the Art.

Abstract: The annoyance-reaction is one of the central variables in noise research After an introduction to different concepts and definitions of noise annoyance different scales of how noise annoyance can be measured are shown The question is discussed whether disturbance effects of noise at different times of day are given To clarify this problem, the results of a series of actual German noise studies are reported In these studies differences between day- and night­time annoyance are found depending on the sound sources For the case of road traffic noise no differences between day and night-time annoyance were found In contrast, annoyance reactions are related to the time of day for railway and air traffic noise Especially for aircraft noise, above a Leq of 50 dB(A) night-time annoyance rises faster than day-time annoyance The effects are discussed in the frame of a cognitive model of noise annoyance It is argued that annoyance judgments are based on an internal representation of the noise situation Part of this representation are the event characteristics of the sound sources and their estimated impacts for disturbances at different times of day

Experiments on effects of an intermittent 16.7-Hz magnetic field on salivary melatonin concentrations, rectal temperature, and heart rate in humans.

Abstract: Objectives: The present experiments concerned the hypothesis that an intermittent, strong and extremely low frequency magnetic field reduces salivary melatonin levels and delays consecutively the nadirs of rectal temperature and heart rate. Methods: Twelve healthy young men (18–25 years) participated in three randomly permuted sessions, which were performed as constant routines. The participants kept a strict bed rest over 26 h, air temperature was 20 °C, illumination <30 lx, and sound level <50 dBA. Salivary melatonin levels were determined hourly, rectal temperature and heart rate were registered continuously throughout. An intermittent magnetic field was administered in one session from 6 p.m. to 2 a.m. at 16.7 Hz, 0.2 mT and alternating on/off-periods of 15 s. This situation was compared with a control session without any additional stress. Another session was performed to determine the participants' ability to respond to a well-known melatonin-suppressing stress, namely bright light (1,500 lx, 10 p.m.–2 a.m.). Results: Bright light inhibited melatonin synthesis in all 12 participants and delayed the nadirs of rectal temperature and heart rate. The only significant alteration that was associated with exposure to the magnetic field was a delay in the heart rate nadir, which was not mediated by an accordingly altered melatonin profile. Conclusion: The fact that the circadian rhythm of only the heart rate was altered indicates an internal dissociation which might constitute a health risk in the long run and needs to be investigated more extensively.

Effects of electromagnetic radiation (bright light, extremely low-frequency magnetic fields, infrared radiation) on the circadian rhythm of melatonin synthesis, rectal temperature, and heart rate.

Abstract: Electromagnetic spectra reduce melatonin production and delay the nadirs of rectal temperature and heart rate. Seven healthy men (16-22 yrs) completed 4 permuted sessions. The control session consisted of a 24-hours bedrest at < 30 lux, 18 degrees C, and < 50 dBA. In the experimental sessions, either light (1500 lux), magnetic field (16.7 Hz, 0.2 mT), or infrared radiation (65 degrees C) was applied from 5 pm to 1 am. Salivary melatonin level was determined hourly, rectal temperature and heart rate were continuously recorded. Melatonin synthesis was completely suppressed by light but resumed thereafter. The nadirs of rectal temperature and heart rate were delayed. The magnetic field had no effect. Infrared radiation elevated rectal temperature and heart rate. Only bright light affected the circadian rhythms of melatonin synthesis, rectal temperature, and heart rate, however, differently thus causing a dissociation, which might enhance the adverse effects of shiftwork in the long run.

Melatonin synthesis : a possible indicator of intolerance to shiftwork

Abstract: Hypothesis Melatonin synthesis, which is directly controlled by the central circadian pacemaker indicates the circadian phase better than rectal temperature. Methods: Thirty four men (16-32 years, 7 morning, 13 neither, 14 evening types) performed a constant routine (24-26-hr bedrest, < 30 lux, 18-20°C, hourly isocaloric diet). Salivary melatonin level was determined hourly and rectal temperature was continuously recorded. Results: The nadir of rectal temperature occurred 1.5 hr (P = 0.017), the onset of melatonin synthesis 3 hr earlier (P < 0.0001) in morning than in evening types. Morningness was not related to the quantitative but significantly to the temporal parameters, closer to those of melatonin than of rectal temperature. Conclusions: The melatonin onset is a more reliable indicator of the diurnal type than the nadir of rectal temperature. As morningness has been associated with intolerance to shiftwork, melatonin profiling provides a suitable basis for the establishment of directed preventive measures.