Heat stress can be describes as a condition that is manifested by the inability of the body to use normal regulatory mechanisms to induce cooling. As a result of heat stress, several conditions manifest themselves in the body inform of heat exhaustion, cramps and stroke. The most severe of these is the heat stroke, which usually manifests after body temperature shoots to high levels owing to the inability of the hypothalamus to control the heat through sweating. Several countries depending on their relative location to the sun have calculated different heat stress limits. Canada is one of these countries. According to Weeks et al. (1991), these limits are to help monitor and prevent the development of heat stress in the workplace. This is because any job that is likely to increase the core temperature of the worker creates a high risk of heat stress (Dasler, 1977). This paper will draw a comparison of heat stress limits in Canada at provincial, federal state, and international level.
Exposure to excessive heat is threatening most of the Canadian workers today (Agency for Safety and Health, n.d.). The global patterns of weather are hinging to an increased frequency of heat waves that pose physical hazards to Canadian workers. The American Conference of Governmental Industrial Hygienists (ACGIH) guidelines have found their application in all the Canadian provinces as the measure of curbing heat stress(Pimenta et al. 1992). The ACGIH uses Wet Bulb Globe Temperature (WBGT) to calculate the Threshold Limit Values (TLVs). These provinces use these to ensure that the core temperature of the workers is not let to go past the 380C mark.
The federal government of Canada uses ACGIH guidelines in setting of maximum and minimum temperatures. These limits are in respect to personal service food preparation area, first aid room and operators compartments. The limit is 180c minimum and 290c maximum. Most of the provinces use the ACGIH TLVs for heat and cold exposure limits in work place and different places in their areas with an exception of Quebec, which uses WBGT, which is similar to the ACGIH guidelines, and Yukon Territory, which uses heat stress limits only(Centre for Occupational Health and Safety, 2010). The provinces using acgih are Alberta, Ontario, Saskatchewan, Manitoba, Nova Scotia, New Brunswick, Nunavut, British Columbia, Newfoundland, Labrador, Prince Edward Island, and North West territories. New Brunswick and Prince Edward Island have the most elaborate heat limit categories, with each of them having lowest limit set to 120 c while under heavy work. The tables below show various heat stress limits and regulation measures in these provinces based on the scales used in each of them.
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Apart from the ACGIH index, the Canadian government uses the Humidex scale to inform the public about the outdoor heat limits and the required activity. This index considers the air temperature and the relative humidity at any given time. A humidex value of over 460 would see the government restrict labor to avoid development heat stress disorders.
On international comparison, Hong Kong uses the internationally accepted occupational limits, which are based on ACGIH guidelines that Canada uses. However, in Japan, the heat stress limits are set by the Japanese Association of Industrial Health that recommends the use of Permissible Exposure Limits (PELS). These PELS are the same the ACGIH TLVS. In New Zealand, the heat stress limits are set by the Workplace Exposure Standards (WES), which are equivalent to OELs. The United States of America, uses a combination of these standards in measuring and determining the heat exposure limits. These include the ACGIH and the PEL (Permissible Exposure Limits) published by the occupational safety health administration. The wet bulb temperature, which seems to, be used by many countries in calculating the ACGIH values is a consideration of the temperature, atmospheric humidity and is equated to the feeling on the skin when exposed to moving air. This considers that the core body temperature is at 370 c thus, skin temperature is regulated at temperatures below 350c to facilitate dissipation of heat.
Many challenges are faced in setting these heat stress values internationally. These include, the current unpredictable global warming effect owed to the increased production of greenhouse gases, and inability to express the heat index on temperatures below 270 c and 40% humidity. Additionally, there are no standard conversion measures of comparing the different heat stress limits given by different systems. I would recommend that a system be sought that would enable people to understand these limits using the internationally accepted and common units. Moreover, there is need to increase awareness in workers to avoid unnecessary heat related disorders.
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