May 16, 2003

New research shows humidity increases the danger of hot, parked vehicles to young children

Warren, Mich. – General Motors and the National SAFE KIDS Campaign have released alarming new research that shows humidity makes a hot, closed vehicle even more dangerous to young children trapped inside.

The findings, which come just as temperatures are heating up across the nation, provide additional evidence that children should never be left alone in or allowed access to parked vehicles, according to GM and SAFE KIDS executives.

On the average, at least 25 children die each year as the result of being trapped in hot vehicles. Since 1996, GM has identified more than 175 deaths.

“This disturbing news only reinforces our commitment to educating parents and caregivers about the potentially deadly consequences of leaving their children alone in hot vehicles,” said Deb Nowak-Vanderhoef, a GM safety communications director. “We want to help eliminate these tragedies with education, and with sensor technology we are already working on.”

Prior research and real-world incidents have demonstrated that on a warm, sunny day, even at temperatures as mild as 60 degrees Fahrenheit, a closed vehicle can heat up to dangerous levels in minutes, and children left in this environment can face serious injury or even death.

The new study, commissioned by GM of Canada, is the second phase of tests on how heat in closed vehicles affects infants and small children. The first phase, conducted and released in 2001, focused on dry heat and showed that the temperature within a closed vehicle can become dangerous to small children and infants in only minutes. Substituting humid heat for dry heat in the second research phase reduced that window of time by about half because the presence of additional water vapor in the air further diminishes the body’s ability to get rid of heat.

Dr. Oded Bar-Or, director of the Children’s Exercise and Nutrition Centre at McMaster University in Hamilton, Ontario, led both phases of the research with Dr. Boguslaw Wilk. Bar-Or, one of the world’s leading authorities on thermal injury to children, and his team used a climatic chamber to simulate humid heat conditions (98-100.4 degrees F with a relative humidity of 55 percent) in a closed vehicle and determine its effect on children.

Bar-Or and Wilk enlisted 10 male volunteers who sat inside the test vehicle for about 90 minutes as researchers monitored their rectal and skin temperatures, along with other vital signs such as heart rate. The results were mathematically extrapolated to the physiological characteristics of children.

Among the volunteers, many of whom participated in the first phase, rectal temperature, skin temperature and heart rate increased faster and reached higher levels in hot-humid vs. hot-dry conditions. A primary way the body gets rid of heat is through the skin, either through dry heat loss or through sweat. The men were unable to dissipate heat from their body core to their skin within six minutes. When heat can’t be dissipated, it builds up in the body, and heatstroke may occur.

Because a child’s body temperature increases three to five times faster than that of an adult and because children are vulnerable to heat in other ways, “We should assume that (the inability to dissipate heat) occurs at least as fast in babies and infants,” said Bar-Or.

“No parent deliberately exposes their child to what becomes an oven-like temperature. The price they pay for this ignorance and absentmindedness is unimaginable,” said Heather Paul, Ph.D., executive director of the National SAFE KIDS Campaign. “Our job is to convince parents that kids, cars and heat are a deadly combination.”

GM is using Bar-Or’s research to create sensor technology that would alert passersby to the presence of a child or a vulnerable adult trapped in a dangerously hot vehicle. The sensor may also be able to detect a pet. The technology is still under development and is expected to be ready by mid-decade.

For the third year in a row, GM and SAFE KIDS are distributing free brochures, in English and Spanish, that include safety tips and information about the dangers of leaving children unattended in vehicles. They are free and available through the more than 300 SAFE KIDS coalitions nationwide. Order additional brochures at 866-700-0001 (press/choose option No. 2). Or, download the brochure from the GMability and SAFE KIDS web sites, and

For more information on GM’s vehicle safety leadership, please visit

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