Eight laboratories participated in a concerted research project on the assessment of hot working conditions. The objectives were, among others, to co-ordinate the work of the main European research teams in the field of thermal factors and to improve the methods available to assess the risks of heat disorders at the workplace, and in particular the "Required Sweat Rate" model as presented in International Standard ISO 7933 Standard (1989). The scientific bases of this standard were thoroughly reviewed and a revised model, called "Predicted Heat Strain" (PHS), was developed. This model was then used to predict the minute by minute sweat rates and rectal temperatures during 909 laboratory and field experiments collected from the partners. The Pearson correlation coefficients between observed and predicted values were equal to 0.76 and 0.66 for laboratory experiments and 0.74 and 0.59 for field experiments, respectively, for the sweat rates and the rectal temperatures. The change in sweat rate with time was predicted more accurately by the PHS model than by the required sweat rate model. This suggests that the PHS model would provide an improved basis upon which to determine allowable exposure times from the predicted heat strain in terms of dehydration and increased core temperature.
Zusammenfassung Fragestellung Die Vergleichbarkeit mit der internationalen Literatur ist ein entscheidendes Kriterium bei der Wahl von Testinstrumenten. Zur Identifizierung der subjektiven zirkadianen Phasenlage (Chronotyp) werden im deutschen Sprachraum daher meist Übersetzungen des Morningness‐Eveningness‐Questionnaires (MEQ, Horne & Östberg, Int J Chronobiol 4:97 – 110, 1976) angewendet. In der vorliegenden Arbeit wurde die Validität einer deutschen Übersetzung des MEQ (D‐MEQ) geprüft. Als Kriterien dienten der validierte Fragebogen zur subjektiven zirkadianen Phasenlage (SCP, R Moog, in Reinberg, Vieux, Andlauer (eds): night and shift work. Biological and social aspects. Pergamon Press Oxford, 1981) sowie der Nadir der Körperkerntemperatur und der Beginn der nächtlich erhöhten Melatoninkonzentration im Speichel. Methodik 377 Personen (207 Frauen, 170 Männer, 18 – 68 Jahre) beantworteten in wechselnder Reihenfolge den D‐MEQ und den SCP, 43 Personen den D‐MEQ 7 bis 12 Wochen später ein zweites Mal. 50 Personen absolvierten eine Constant Routine (24 Stunden strenge Bettruhe bei einer Beleuchtung < 30 lux, einer Raumtemperatur von 20 °C und in stündlichen Abständen verabreichter isokalorischer Diät). Während dieser Zeit wurde die Rektaltemperatur kontinuierlich registriert und stündlich die Melatoninkonzentration im Speichel bestimmt. Ergebnisse Die Scores beider Fragebögen korrelierten hochsignifikant miteinander (r = – 0,9, p < 0,0001) und resultierten in einer etwa gleich häufigen Zuordnung zu den verschiedenen Chronotypen. Der Chronotyp korrelierte wiederum signifikant mit dem Nadir der Körperkerntemperatur (r = – 0,345, p < 0,014) und dem Beginn der Melatoninsynthese (– 0,606, p < 0,001). Schlussfolgerung Die hier angewandte deutsche Übersetzung des MEQ stellt damit ein valides Instrument zur Identifizierung der individuellen Phasenlage dar.
An improved set of maximum values and limits is described, to be used in the revised version of the ISO 7933 standard. Due to the major modifications to the "Required Sweat Rate" index and in order to avoid any confusion, it is suggested that the revised model be renamed the "Predicted Heat Strain" (PHS) model.
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 degrees C to 38.6 degrees C. Experimental conditions included air temperatures (Ta) between 20 and 55 degrees C, mean radiant temperatures (Tr) up to 145 degrees C, partial vapour pressures (Pa) from 0.2 to 5.3 kPa, air velocities (v(a)) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (T(re)) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation, I(cl),< or = 0.2 clo, where 1 clo = 0.155 m2 x degrees C x 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 degrees C and a humidity of less than 50%) and clothed (0.6 < or = I(cl) < or = 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: T(sk) = 7.19 + 0.064Ta + 0.061Tr + 0.198Pa - 0.348v(a) + 0.616T(re) and T(sk) = 12.17 + 0.020Ta + 0.044Tr + 0.194Pa - 0.253v(a) + 0.0029M + 0.513T(re). For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range of +/- 1 degree 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.