Climate change is expected to increase the frequency, duration and intensity of heat waves, affecting public health. Increased daytime temperatures, reduced nighttime cooling and higher air pollution levels associated with heat events can affect human health. Extreme heat events can trigger a variety of heat stress conditions, such as heat stroke. Heat stroke is the most serious heat-related disorder. It occurs when the body becomes unable to control its temperature. Body temperature rises rapidly, the sweating mechanism fails and the body cannot cool down. This condition can cause death or permanent disability if emergency treatment is not given. Heat cramps and exhaustion are also health impacts of extreme heat exposure. Small children, the elderly and certain other groups including people with chronic diseases, low-income populations and outdoor workers have higher risk for heat-related illness. Higher temperatures and respiratory problems are also linked. One reason is because higher temperatures contribute to the build-up of harmful air pollutants.
People living in cities are already at a higher risk of heat waves because urban areas are warmer than surrounding non-urban areas due to the heat island effect. Tragic heat related crises in Chicago and other cities illustrate that, during extreme heat events, our social systems may not be well equipped to help residents, especially the elderly and otherwise isolated or particularly vulnerable.