Dehydration in hot working environments: assessment, prevention and rehydration procedures

This PhD thesis addresses the problem of dehydration during work in hot environments. Many industries in the UK are affected by problems of dehydration. These include the glass-making and metal refinery industries, ship-building, the nuclear industry, firefighting and firefighter training, and other activities where protective clothing is worn. The thesis is written in five parts, with the following aims: 1) To review current literature and available guidelines on the factors affecting dehydration and rehydration, and study the influence of acclimation. The latter was achieved during a laboratory-based experiment with 8 subjects, where diet and activity were strictly controlled, and a sweat electrolyte collection technique was developed. 2) To identify practical and accurate methods of measuring hydration state, which could be used in laboratory work, and ultimately in field-based work. This included a literature review and two laboratory-based experiments, one of which was an -, extensive repeated measures study using 8 subjects. 3) Several Fire Brigades had expressed concern in the area of dehydration, so a case study was carried out to determine the extent of hydration problems during firefighter training, and provide a solution if a problem was identified. This aim was achieved by taking physiological and subjective measures from 8 fire training instructors and 19 firefighter recruits in their training environment. Following this, a laboratory-based, repeated measures study was carried to assess the physiological and psychological impacts of two controlled drinking regimes versus ad libitum drinking during simulated fire training instructor work. 4) To implement an effective and practical fluid intake regime into firefighter training. This study involved 128 recruits and 88 fire training instructors completing user questionnaires regarding any practical issues that needed to be addressed in order for them to be able to follow the controlled drinking regime. 5) To provide guidance for firefighter recruits and instructors in the form of quick reference information, and where required, more in-depth analyses of body water changes. The results of the thesis are outlined below. When monitoring the hydration state of people who work in the heat, thirst cannot be relied upon as a method for accurately regulating fluid intake. However, the urinary indices of osmolality, specific gravity and colour (and volume to a lesser extent) provide a combination of accuracy and practicality. During the case study with the Fire Service, it was found that firefighter recruits do not experience significant dehydration problems during hot fire trainin ' whereas fire training instructors do. In . 91 an attempt to solve these problems, . twocontrolled . fluid intake regimes were employed. They provided attenuation in physiological strain. compared to ad libitum drinking during simulated fire instructor work in hot ponditiops. Subsequently, it was found that an effective fluid intake regime could be successfully implemented into firefighter training, so long as sufficient provision is made in terms of time and availability of fluids. To accompany the'fWd iýtakeregime, a guidance document, specifically tailored to the Fire Service, on the effects of dehydration and heat strain, and how to reduce those effects, was produc6d. 'Inaddition, more in-depth analysis of body water changes has been provided. Identifying hydration problems and providing solutions (physiological and practical) took placeduringwork with the Fire Service in this thesis; however the process has generic properties and could be applied elsewhere.