Dec '09/Jan '10


Managing heat stress: Collaboration benefits the mining industry

By S. Hardcastle and G. Kenny

A researcher from the University of Ottawa participating in field-based heat stress research to explore problems in hot and deep mines. The subject is fitted with thermocouple patches for the measurement of skin temperatures and an oxygen analyzer to estimate the metabolic energy used during work at Agnico-Eagle and Vale Inco mines.

With a changing surface climate, greater depth and continued mechanization of larger equipment, Canadian underground mine workers have an increasing risk to be exposed to heat stress. This is not only a health and safety issue for the worker but also a productivity and cost issue for the mining company. Even before experiencing the more serious consequences of heat stress, heat syncope (fainting), heat strain and its associated fatigue can lead to a decline in both a worker’s physical performance and mental ability, which in turn can cause an increase in both non-specific lost time injuries and accidents.

Heat exposure management, through specified work-to-rest protocols, can also reduce the productive time that could be expected from a worker. Heat control, through the use of more ventilation or cooled air, becomes a very expensive and possibly prohibitive constraint in deep, highly mechanized mines. Consequently, understanding how our bodies thermoregulate, and controlling heat stress in such hostile environments is of major interest to the mining industry and the focus of a major Deep Mining Research Consortium (DMRC) effort.

Over the past few decades, significant progress has been made in the understanding of human physiology during heat stress. However, despite industry’s extensive implementation of procedures to mitigate the development of heat stress symptoms, the risk of heat-related injuries remains a major problem. Over the past 15 years, the University of Ottawa’s Human and Environmental Physiology Research Unit has been conducting a comprehensive and cutting-edge research program directed at advancing our understanding of the physiological effects and consequences of heat stress in at-risk populations and, in particular, industrial workers, such as miners, performing in arduous environments. This unit’s research facility presently houses the world’s only functional human air calorimeter with a capacity to accurately measure, minute by minute, the rates of whole-body heat exchange, as well as the change in body heat content. Combining the traditional physiological parameters (core and skin temperatures, sweat-rate etc.) with whole-body calorimetry has led to the development of valuable new insights on how environmental and non-environmental factors affect the development of thermal stress in humans.

Since late 2004, the University of Ottawa, in partnership with industry through the DMRC, and with government through Natural Resources Canada’s CANMET Mining & Mineral Science Laboratories, have conducted studies to examine the problems faced by the industry as it relates to personnel heat exposure issues. The early phases of the program involved the evaluation of the physical demands and energy cost of common mining occupations under non-heat stressed conditions at Agnico–Eagle’s LaRonde Mine. This work demonstrated the diversity and differing intensity of the numerous tasks miners perform in Canada’s mechanized operations. It also showed how general services, bolting and shotcrete have significantly higher metabolic energy expenditures than the production-orientated drill, blast and mucking occupations.

Further studies at Vale Inco’s Garson Ramp project showed that mine rescue activities have much higher average energy expenditures — nearly twice that of any of the other mining occupations. Once categorized in situ at the mines, all the activities were replicated under controlled environmental conditions in a laboratory. Here, volunteers could be monitored continuously and in greater detail to establish energy input and output, changes in core and skin temperatures, heat loss and heat storage.

Also, depending on the temperature, the laboratory could identify which miners performing which task are increasingly at risk. This has since led to the first continuous real-time studies into the insulative properties of clothing worn by miners and their work-to-rest cycles using human subjects in a calori­meter. This work will lead to establishing the optimal clothing and defining best practices for work and rest.

Future studies are planned to actually define the effects of heat acclimation on the human body, how it is attained and over what period it is lost. All of this work will be compiled into a guideline/best practices document for the industry.

However, there are numerous other considerations that affect human thermoregulation, including hydration, age, fitness, gender, health and medication. In association with DMRC, the Ontario WSIB is funding studies looking at age and fitness in light of the aging mining workforce. NSERC supported the innovative development of a micro-climate cooling garment using membrane-based technology. Most recently, the Canada Foundation for Innovation committed to financing the continued improvement of the calorimeter and associated facilities.

The management and other non-physiological aspects of this project — such as addressing the accurate measurement of environmental variables in deep mines — have been undertaken by CANMET-MMSL. Industrial champions for this work as it progressed included Agnico-Eagle and, more recently, Vale Inco. Other bodies participating in the research include the Mines and Aggregates Safety and Health Association’s Ontario Mine Rescue Program.

This is an excellent example of how academic and government research, funded by industry, research and safety agencies, can work together to help mines be safer and more productive. The outcome of this work is also garnering the interest of the military and agencies such as Health Canada as they consider which sub-populations may be at risk in hot climates and with continuing climate change.

Stephen Hardcastle is a senior scientist with Natural Resources Canada, head of mine ventilation research within CANMET Mining and Mineral Sciences Laboratories, and an Adjunct Professor at the Laurentian University. Currently, he is managing a suite of heat stress-oriented projects for Canada’s Deep Mining Research Consortium and the research aspects of a ventilation-on-demand initiative with the Centre for Mining Innovation.

Glen Kenn, a professor and the director of the Human and Environmental Physiology Research Unit at the University of Ottawa, is a leading authority in the area of human thermoregulation. His work is directed at improving the understanding of the human physiological responses to work performed in adverse environments. This research is playing a key role in providing valuable information aimed at improving the health and safety of Canadian workers.

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