heat exposure - the inside story

The human body must maintain a narrow temperature range. Control mechanisms in the body adapt to changes in the environment and help regulate the body’s internal temperature. When the body is exposed to heat, blood vessels in the skin expand, bringing warm blood to the surface to be cooled. Sweat glands in the skin release fluid onto the skin surface where it evaporates, transferring heat from the blood vessels to the external environment and cooling the body in the process.

The body releases water through the sweat glands so that when the water evaporates off the surface of the skin, the blood just under the skin is cooled.

Most people readily adjust to increased temperatures. But when a body can’t regulate internal temperature, problems develop, including problems that are potentially life-threatening. This is especially the case in the workplace, where hot temperatures can combine with job-related stresses to result in serious medical conditions or even death.

There are on average 274 heat-related deaths in the United States each year, but the number is thought to be much higher.

The three main problems associated with excessive exposure to heat are the following: 

• Heat cramps
• Heat exhaustion
• Heat stroke

Heat cramps are usually minor in nature. They typically result from a combination of vigorous physical activity and poor replacement of fluid to the body. Leading to dehydration- an excessive loss of water from the body. The initial affects are cramping in the leg and abdominal muscles.

Heat exhaustion, also known as heat prostration or heat collapse, is a little more serious - a mild form of shock. Shock is a potentially life-threatening condition of inadequate blood flow to the body's tissues. It can be characterized by restlessness, anxiety, cold and clammy skin, and/or an altered level of responsiveness. Shock is the most common illness associated with heat exposure. It results from the loss of water and elements called electrolytes (elements, such as calcium and sodium, that the body uses in blood and other body fluids to conduct necessary cell functions) typically through sweating. This leads to hypovolemia, a condition of lowered fluid in the body which decreases the ability to deliver oxygen to body tissues.

The most serious heat-related illness is heat stroke. Heat stroke occurs when the body is subjected to more heat than it can handle and normal mechanisms for getting rid of excess heat, such as sweating, break down. This results in a rise in body temperature to a level at which sensitive nervous system tissue can be injured. If untreated, heat stroke can result in severe brain damage and even death.