213 Heat-Related Illness Occupational heat exposure poses a threat to the health and safety of many workers. Exposure to heat from extreme environmental temperatures or heat generated by the body itself from overexertion during work activities can lead to serious health implications. When the body’s natural ability to dissipate heat is impaired by varying internal and ex- ternal factors, heat-related illnesses can occur (Wexler, 2002). Exposure to high temperatures can lead to a progres- sion of symptoms in the body which can result in widespread tissue damage, organ damage, and even death, if not treated in a timely and effective manner. The heat index chart depicted in the following figure shows the effect or “apparent temperatures” when heat and humidity are combined. The heat index is the cell where these two measures intersect and gives an idea of how combined heat and humidity in the air make us feel. For example, an air temperature of 90°F and a relative humid- ity of 60 percent intersect at a heat index of 100°. Therefore, the temperature would feel more like 100° with this humidity and temperature combination. The chart also indicates the range of outcomes (i.e., fatigue, sunstroke) de- pending on the apparent temperature reached. Symptoms of hyperthermia may range from mild fatigue, headache, or nausea progressing to confusion and convulsions with eventual loss of consciousness and even death with latter symptoms deemed a medical emergency. Exposure to full sunshine can increase the heat index by 15°. Heat Index Chart Heat index (or apparent temperature) chart showing various combinations of air temperature versus relative humidity. Air temperature measured in Fahrenheit (F). Source: Reprinted with permission from Watts, A. 2006. Heat index chart. Retrieved November 11, 2006, from www.tvweather.com/awpage/heat_index_chart.htm. Guideline continues on next page