Barbara Griefahn

Maximal physical work performance with European standard based fire-protective clothing system and equipment in relation to individual characteristics

Every fire fighter needs to wear fire-protective clothing and a self-contained breathing apparatus (SCBA) several times a year while carrying out various fire-fighting and rescue operations in hazardous work environments. The aim of the present study was to quantify the effects of a multilayer turnout suit designed to fulfil European standard EN 469 used over standardized (Nordic) clothing and with SCBA (total mass 25.9 kg) on maximal physical work performance, and to evaluate the relationship between individual characteristics and power output with the fire-protective clothing system and SCBA. The subjects were 12 healthy firemen aged 26–46 years. The range of their body mass, body fat and maximal oxygen consumption was 69–101 kg, 10–20% and 2.70–5.86 1·min−1, respectively. The maximal tests without (control) and with the fire-protective clothing system and SCBA were carried out on a treadmill in a thermoneutral environment. When compared to the control test, the decrease in the maximal power output in terms of maximal working time and walking speed averaged 25% (P < 0.001) varying from 18% to 34% with the fire-protective clothing system and SCBA. At maximum, no significant differences were found in pulmonary ventilation, absolute oxygen consumption, the respiratory exchange ratio, heart rate, systolic blood pressure, the rate-pressure product, mechanical efficiency, and the rating of perceived exertion between the tests with and without the fire-protective clothing system and SCBA. The reduction of the power output was related to the extra mass of the fire protective clothing and SCBA. In this study, robust build and parameters associated with good anaerobic capacity were the most powerful individual characteristics contributing to the smallest drop in the power output with the fire-protective clothing system and SCBA. All possible means to decrease the mass of both the fire-protective clothing system and SCBA for maintaining the sufficient power output in physically demanding fire-fighting and rescue tasks need to be considered.

The associations between noise sensitivity, reported physical and mental health, perceived environmental quality, and noise annoyance.

One hundred and ninety residents around Frankfurt Airport (46% female; 17-80 years) were interviewed concerning noise annoyance due to transportation noise (aircraft, road traffic), perceived mental and physical health, perceived environmental quality, and noise sensitivity. The aim of the analyses was to test whether noise sensitivity reflects partly general environmental sensitivity and is associated with an elevated susceptibility for the perception of mental and physical health. In this study, the reported physical and mental health variables were not associated with noise exposure but with noise annoyance, and were interpreted to reflect nonspecific codeterminants of annoyance rather than noise effects. Noise sensitivity was found to influence total noise annoyance and aircraft noise annoyance but to a lesser degree annoyance due to road traffic noise. Noise sensitivity was associated with reported physical health, but not with reported mental health. Noise-sensitive persons reported poorer environmental quality in their residential area than less sensitive persons in particular with regard to air traffic (including the facets noise, pollution, and contaminations) and quietness. Other aspects of the perceived quality of the environment were scarcely associated with noise sensitivity. This indicates that noise sensitivity is more specific and a reliable predictor of responses to noise from the dominant source (in this case air traffic) rather than a predictor of the individual perception of the environmental quality in general.

Event-related awakenings caused by nocturnal transportation noise.

The present study focussed on awakenings caused by nocturnal noises emitted from aircraft, road and rail vehicles with maximum levels ranging from 40 to 76 dBA. A laboratory study with 24 participants (12 male, 12 female, 19-28 years) was performed with polysomnographic recordings during 13 nights (including a preceding habituation night). Multivariable random subject effect logistic regression models containing acoustical, situational and individual parameters were used to determine the probability of event-related awakenings for each traffic mode. Awakening probability increased significantly with maximum sound pressure level (SPL), slope of rise (dB/s), noise duration and the noise-free interval between noise events. Gender, noise sensitivity and age did not influence awakening probability significantly (the latter only in a combined model). Awakening probability increased with elapsed time after sleep onset, and was significantly lower during slow wave sleep compared to S2 sleep, but not during REM sleep. After adjusting for differences in study design (acoustical macrostructure), awakening probability decreased in the order rail, road and air traffic noise, but only rail and air traffic noise differed significantly (p= 0.002). After further adjusting for slope of rise and noise duration (acoustical microstructure), differences between traffic modes decreased, but rail and air traffic noise still differed significantly (p=0.044). Acoustical properties other than slope of rise and noise duration may account for the residual difference. The results of this study suggest that the reduction of maximum SPLs, rise slopes, and traffic volume during the second part of the night might reduce the number of noise-induced awakenings.

Melatonin production during childhood and adolescence: a longitudinal study on the excretion of urinary 6-hydroxymelatonin sulfate.

Abstract: Cross‐sectional data on urinary 6‐hydroxymelatonin sulfate (6‐OHMS) excretion in children suggest a constant melatonin secretion during growth. The present longitudinal study concerned, accordingly, the intra‐individual stability of melatonin production during childhood and adolescence. Urine samples collected during a longitudinal investigation of healthy white children and adolescents were analyzed. Forty‐six boys and 38 girls were chosen for the present study. They had passed 3–15 annual examinations between their 3rd and 18th yr of age. Each examination included the collection of urine over 24 hr. The daily urinary output of 6‐OHMS of the overall 621 samples was quantified by enzyme‐linked immunosorbent assay. The analyses clearly revealed for the first time that, despite huge inter‐individual differences, melatonin production remains constant in one and the same individual during childhood and adolescence. Additionally, neither a significant sex difference was observed nor was the 6‐OHMS output affected by season. The dramatic decrease of plasma melatonin levels as described in the literature is mainly related to an increase in body size rather than to decreasing pineal secretion.

Prediction of the average skin temperature in warm and hot environments

Abstract The prediction of the mean skin temperature used for the Required Sweat Rate index was criticised for not being valid in conditions with high radiation and high humidity. Based on a large database provided by 9 institutes, 1999 data points obtained using steady-state conditions, from 1399 experiments and involving 377 male subjects, were used for the development of a new prediction model. The observed mean skin temperatures ranged from 30.7 °C to 38.6 °C. Experimental conditions included air temperatures (Ta) between 20 and 55 °C, mean radiant temperatures (Tr) up to 145 °C, partial vapour pressures (Pa) from 0.2 to 5.3 kPa, air velocities (va) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (Tre) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation, Icl, ≤0.2 clo, where 1 clo=0.155 m2 · °C · W−1, which is equivalent to the thermal insulation of clothing necessary to maintain a resting subject in comfort in a normally ventilated room, air movement=10 cm/s, at a temperature of 21 °C and a humidity of less than 50%) and clothed (0.6 ≤ Icl ≤ 1.0 clo) subjects using a multiple linear regression technique with re-sampling (non-parametric bootstrap). The following expressions were obtained for nude and clothed subjects, respectively: Tsk=7.19 + 0.064Ta + 0.061Tr + 0.198Pa− 0.348va + 0.616Tre and Tsk=12.17 + 0.020Ta + 0.044Tr + 0.194Pa − 0.253va + 0.0029M + 0.513Tre. For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range of ±1 °C of the observed skin temperatures. It is concluded that the proposed models for the prediction of the mean skin temperature are valid for a wide range of warm and hot ambient conditions in steady-state conditions, including those of high radiation and high humidity.

Aircraft noise effects on sleep: mechanisms, mitigation and research needs.

There is an ample number of laboratory and field studies which provide sufficient evidence that aircraft noise disturbs sleep and, depending on traffic volume and noise levels, may impair behavior and well-being during the day. Although clinical sleep disorders have been shown to be associated with increased risk of cardiovascular diseases, only little is known about the long-term effects of aircraft noise disturbed sleep on health. National and international laws and guidelines try to limit aircraft noise exposure facilitating active and passive noise control to prevent relevant sleep disturbances and its consequences. Adopting the harmonized indicator of the European Union Directive 2002/49/EC, the WHO Night Noise Guideline for Europe (NNG) defines four Lnight , outside ranges associated with different risk levels of sleep disturbance and other health effects ( < 30, 30-40, 40-55, and> 55 dBA). Although traffic patterns differing in number and noise levels of events that lead to varying degrees of sleep disturbance may result in the same Lnight , simulations of nights with up to 200 aircraft noise events per night nicely corroborate expert opinion guidelines formulated in WHOs NNG. In the future, large scale field studies on the effects of nocturnal (aircraft) noise on sleep are needed. They should involve representative samples of the population including vulnerable groups like children and chronically ill subjects. Optimally, these studies are prospective in nature and examine the long-term consequences of noise-induced sleep disturbances. Furthermore, epidemiological case-control studies on the association of nocturnal (aircraft) noise exposure and cardiovascular disease are needed. Despite the existing gaps in knowledge on long-term health effects, sufficient data are available for defining limit values, guidelines and protection concepts, which should be updated with the availability of new data.

The cortisol awakening response: a pilot study on the effects of shift work, morningness and sleep duration.

This study concerned the possible influence of experimental shift work, morningness and sleep length on the cortisol awakening response (CAR). Eight morning-oriented (MT) and eight evening-oriented (ET) healthy young men (19-27 years) slept after three consecutive day shifts during the night and after three consecutive night shifts during the day in the laboratory. Salivary cortisol concentrations were ascertained after each sleep period upon awakening and half an hour later, half-hourly during work shifts, and hourly during two 24-h periods, after the three day shift/night sleep sequences and after the three night shift/day sleep sequences. Statistical analyses considered the temporal position of sleep (night, day), the succession of sleep periods, the diurnal type and the polysomnographically verified total sleep time. The CAR was significantly smaller after day than after night sleep and increased significantly with total sleep time in ET. MT had moderately higher cortisol concentrations upon awakening than ET probably because they wake up at a later time of their circadian rhythm. But neither the CARs nor the cortisol concentrations during the following work shifts or during the 24h profiles were different in both diurnal types. The cortisol concentrations during work shifts correlated significantly with the previous post-awakening concentrations in MT but not in ET. Due to the small samples further studies are needed.

The impact of draught related to air velocity, air temperature and workload

This experimental study was designed to test the hypotheses that the effects of draught increase with higher air velocity, with lower air temperature, and with lower workload. Thirty healthy young males were exposed to horizontal draught during 55 min while they operated an arm ergometer in a standing posture. Air velocity, air temperature, and workload were varied in 3 steps each, between 11 and 23 degrees C, 0.1 and 0.3 m/s, and 104 to 156 W/m2, respectively. The 27 combinations were distributed over subjects in a fractional factorial 3(3)-design. The participants were clothed for thermal neutrality. Workload was measured at the end of the sessions by respirometry. Draught-induced annoyance was determined every 5 min, separately for 10 body sites. Corresponding skin temperature was also recorded. The hypotheses were verified for the influence of air velocity and air temperature. Regarding workload, local heat production is probably decisive, meaning that draft-induced local annoyance is inversely related to workload in active but independent from workload in non-active body areas. To improve the situation for the workers concerned it is suggested to apply protective gloves that cover an as great area of the forearms as possible and to limit airflows to mean velocities of less than 0.2 m/s (with turbulence intensities of 50%).

Evaluation of performance and load in simulated rescue tasks for a novel design SCBA: effect of weight, volume and weight distribution.

A self-contained breathing apparatus (SCBA) with an innovative rucksack shape that provides a better distribution of its weight over the middle and lower parts of the back (device C: 6l, 13.7 kg) was compared with two conventional SCBA which differed from each other in volume and weight (A: 6l, 15 kg, B: 6.8l, 11.7 kg). Twelve fire-fighters (27-49 yr) performed three exercises while using the three SCBA in a systematically permuted sequence. The exercises consisted of simulated rescue work under natural climatic conditions in a dwelling on the second floor and several typical elements of severe fire-fighting actions. Duration, heart rate, breathing frequency, rectal temperature, and sweat loss were recorded. Perceived exertion was rated and the carrying features of the SCBA were subjectively evaluated. The exercise was executed faster with the rucksack device, heart rates were then lower and the carrying features were evaluated as better. Thus, the weight of the SCBA was shown to be less important than its distribution.

Melatonin synthesis: A possible indicator of intolerance to shiftwork

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. Am. J. Ind. Med. 42:427–436, 2002.