**5. Who is at risk?**

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.

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

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 nature, they often relate to how you feel. Exposure to more heat stress for a longer duration can cause health problems which impair workers' ability to execute the task and may cause adverse health effects [10]. The body temperature increases because of internal heat production during muscular activity in work place. If the ambient temperature is more than the body temperature, then the heat loss from the body will be minimized by conduction, convection, radiation. As a result the core body temperature will keep increasing and may result in heat related illness such as heat rash, heat syncope, heat exhaustion, heat stroke. The heart rate also increases to pump more blood through skin so that excess heat can be lost to the environment through sweating [14]. These changes will cause additional load on the body. Changes in blood flow and excessive sweating will lead to decrease in person's ability to do physical and mental work [8]. When the environmental temperature rises above 30°C, it may interfere with the performance of mental tasks [14]. The occupational heat stress can affect the workers health either directly or indirectly. The direct health impacts include the heat related illness such as heat rash, heat syncope, heat edema, heat exhaustion and heat stroke [6, 14]. The indirect health impacts include physical and mental stress, hypertension, diabetes mellitus and chronic kidney disease.

Heat rashes are the red spots on the skin which cause a prickling sensation during heat exposure. Heat edema is swelling which generally occurs among people who are not acclimatized to working in hot conditions. Heat cramps are sharp pains in the muscles that may occur as a result of salt imbalance resulting from the failure to replace salt lost due to sweating. Heat exhaustion is caused by excessive loss of body water and salt through excessive sweating. Heat syncope is heat-induced giddiness and fainting because of insufficient flow of blood to the brain while a person is standing which is caused by the loss of body fluids through sweating. Heat stroke is the most serious types of heat illnesses. The body temperature often increases more than 41°C.
