Agenda - 05-06-2010 - 4m - Laserfiche WebLink

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Heat Waves Heat kills by taxing the human body beyond its abilities. In a normal year, about 175 Americans succumb to the demands of summer heat. Among large natural hazards, only the cold of winter—not lightning,hurricanes, tornadoes, floods, or earthquakes—takes a greater toll. In the 40-year period from 1936 through 1975, nearly 20,000 people in the United States were killed by the effects of heat and solar radiation. In the disastrous heat wave of 1980, more than 1,250 people died as a direct result of the heat wave. People at higher risk,e.g., with aging or diseased hearts, are especially susceptible to excessive heat. In recent years,the National Weather Service (NWS)has stepped up efforts to more effectively alert the general public and appropriate authorities to the hazards of heat waves and prolonged excessive heat/humidity episodes. (Source:National Oceanic and Atmospheric Administration(NOAA)) How Heat Affects the Body Human bodies dissipate heat by varying the rate and depth of blood circulation,by losing water through the skin and sweat glands, and -- as the last extremity is reached--by panting, when blood is heated above 98.6 degrees. As heat rises,the heart begins to pump more blood,blood vessels dilate to accommodate the increased flow, and the bundles of tiny capillaries threading through the upper layers of skin are put into operation. Blood is circulated closer to the skin's surface, and excess heat drains off into the cooler atmosphere. At the same time, water diffuses through the skin as perspiration. The skin handles about 90 percent of the body's heat dissipating function. Sweating, by itself, does nothing to cool the , body,unless the water is removed by evaporation-- and high relative humidity retards I evaporation. Heat disorders generally have to do with a reduction or collapse of the ability of the body to shed heat by circulatory changes and sweating, or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body's inner core begins to rise and heat related illness may develop. Ranging in severity, heat disorders share one common feature: the individual has overexposed or over exercised for his/her age and physical condition in the existing thermal environment. Sunburn,with its ultraviolet radiation burns,can significantly retard the skin's ability to shed excess heat. Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age--heat cramps in a 17-year-old may be heat exhaustion in someone 40 and heat stroke in a person over 60. Heat Index . The heat index, given in degrees Fahrenheit, is an accurate measure of how hot it really feels when the relative humidity is added to the actual air temperature(see Heat Index Chart below). If the air temperature is 95°F(found on the left side of the chart), and the relative humidity is 50% (found at the top of the chart),the heat index-or how hot it really feels -is 105°F. This is at the intersection of the 95° row and the 50% column. Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase these values by up to 15°F. Also, strong winds,particularly with very hot,dry air, can be extremely hazardous. The shaded zone above 95°F in the chart corresponds to a heat index 14