**4. Heat stress and heat strain indicators**

There are many indices that are used to assess heat stress such asWet bulb Globe Thermometer (WBGT), Universal Thermal Climate Index, Humidex, etc. WBGT is the gold standard internationally accepted indices for measuring heat stress and it was used to measure the heat stress in most of the previous research work conducted in different occupational sectors [19] (**Figure 1**).

**Figure 1.** *WBGT.*

A wide range of clinical observations and measurement have been used to indicate heat strain, ranging from perception of workers, observational parameter like skin rash to hospitalization due to heat stroke. Most of the previous studies on assessing the health effects have been conducted on simulation settings rather than actual field settings. Such studies although provides us with important information on the relationship, it might not be possible to use the same methodology at work place. The heat strain parameters that were measured in the previous studies include core body temperature [20], Skin temperature [14], Sweat rate [21], Resting/working heart rate [22], Urinary specific gravity [23], Serum creatinine, Serum electrolytes, VO2 Max [14]. The most commonly used heat strain indicators in previous studies are core body temperature, resting heart rate, working heart rate, recovery heart rate and sweat rate. These are done in non invasive manner, so it is easy to perform in field based study. Other parameters such as urine specific gravity, serum electrolytes, creatinine, Vo2 max though reliable but could not be used in the field based study due to the constraints faced in working environment. In fact, these parameters were used in experimental set up study rather than actual field based study. Methods to measure these parameters vary in different study. The most commonly used instrument to measure the core body temperature is through tympanic thermometer as tympanic temperature is the reliable, convenient and most easily accessible site to measure core body temperature (**Figure 2**). Polar heart rate monitor was used to measure the different heart rate in working environment as it is capable of recording continuous heart rate (**Figure 3**). Sweat rate was measured by using the body weight and fluid intake and output of the worker during the working period. The most commonly preferred method to measure the heat strain indicators is to check the pre exposure and post exposure values of these parameters as it can be compared with the standard values given by ACGIH, OSHA etc.

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**5. Who is at risk?**

*Polar heart rate monitor.*

**Figure 3.**

Elderly people above 50 years, pregnant women, workers with other co morbid conditions are at increased risk of developing heat related illness. Most of the functions of the human organs are dependent on the temperature and pH. So if there is alteration in any of these two, then it will definitely have impact on other functions of human body. Workers with history of diabetes mellitus, hypertension, and thyroid disorder are at increased risk as it will cause extra burden to the various organs while working in hot environment. Workers at risk of heat stress include outdoor workers such as agriculture, brick industry, construction and indoor occupation such as firefighters, bakery workers, miners, boiler room workers, factory workers. The major reason that working people belongs to vulnerable group is because of internal heat produced when muscles are used during work [14]. Some people tend to keep working beyond the safe limit for heat exposure because of their need to complete work tasks during a particular period or their need to maintain work output to get paid [24]. During prolonged work periods in the heat, the high sweat rates leads to progressive dehydration. It has been well documented that losses of fluids through sweating can lead to dehydration which has a detrimental effect on productivity.

When the air temperature or humidity rises above the optimal ranges for comfort, can leads to health impacts [14]. The initial effects are subjective in

**6. Health hazards due to heat stress exposure**

*Occupational Heat Stress: A Technical Scan DOI: http://dx.doi.org/10.5772/intechopen.93900* *Occupational Heat Stress: A Technical Scan DOI: http://dx.doi.org/10.5772/intechopen.93900*

*Occupational Wellbeing*

ACGIH, OSHA etc.

A wide range of clinical observations and measurement have been used to indicate heat strain, ranging from perception of workers, observational parameter like skin rash to hospitalization due to heat stroke. Most of the previous studies on assessing the health effects have been conducted on simulation settings rather than actual field settings. Such studies although provides us with important information on the relationship, it might not be possible to use the same methodology at work place. The heat strain parameters that were measured in the previous studies include core body temperature [20], Skin temperature [14], Sweat rate [21], Resting/working heart rate [22], Urinary specific gravity [23], Serum creatinine, Serum electrolytes, VO2 Max [14]. The most commonly used heat strain indicators in previous studies are core body temperature, resting heart rate, working heart rate, recovery heart rate and sweat rate. These are done in non invasive manner, so it is easy to perform in field based study. Other parameters such as urine specific gravity, serum electrolytes, creatinine, Vo2 max though reliable but could not be used in the field based study due to the constraints faced in working environment. In fact, these parameters were used in experimental set up study rather than actual field based study. Methods to measure these parameters vary in different study. The most commonly used instrument to measure the core body temperature is through tympanic thermometer as tympanic temperature is the reliable, convenient and most easily accessible site to measure core body temperature (**Figure 2**). Polar heart rate monitor was used to measure the different heart rate in working environment as it is capable of recording continuous heart rate (**Figure 3**). Sweat rate was measured by using the body weight and fluid intake and output of the worker during the working period. The most commonly preferred method to measure the heat strain indicators is to check the pre exposure and post exposure values of these parameters as it can be compared with the standard values given by

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**Figure 2.**

*Tympanic thermometer: (a) quest temp personal monitor, (b) Infrared tympanic thermometer.*

**Figure 3.** *Polar heart rate monitor.*
