It only takes an hour for a hot car to become deadly

Researchers at Arizona State University (ASU) have investigated how quickly various types of cars warm up when exposed to different levels of shade and sunlight on hot days. They found that the dashboard of a car can reach 160 degrees in an hour, which is about the same amount of time that it would take for a child trapped inside to have a heatstroke.

So far this year, six children left in hot cars in the United States have died, and this number is expected to rise. Every year in the United States, an average of 37 children die from hyperthermia in hot cars. Over half of these deaths are caused when a parent or caretaker forgets that their child has been left in the car.

Nancy Selover is a climatologist and research professor in ASU’s School of Geographical Sciences and Urban Planning.

“Our study not only quantifies temperature differences inside vehicles parked in the shade and the sun, but it also makes clear that even parking a vehicle in the shade can be lethal to a small child,” said Professor Selover.

The researchers used identical pairs of mid-size sedans, economy cars, and minivans for the study. While outdoor temperatures were in the 100s, the team moved the cars from sunlight to shade for different time intervals throughout the day, measuring surface and interior air temperatures.

“These tests replicated what might happen during a shopping trip,” said Professor Selover. “We wanted to know what the interior of each vehicle would be like after one hour, about the amount of time it would take to get groceries. I knew the temperatures would be hot, but I was surprised by the surface temperatures.”

Among vehicles parked in the sun, the average cabin temperature hit 116 degrees in just one hour. Dashboards reached an average of 157 degrees, steering wheels reached 127 degrees, and seats heated up to 123 degrees in the same time frame.

For vehicles parked in the shade, interior temperatures averaged 100 degrees after an hour. Dashboards hit 118 degrees, steering wheels reached 107 degrees, and seats warmed up to 105 degrees. In addition, the economy car heated up faster than the mid-size sedan and minivan.

“We’ve all gone back to our cars on hot days and have been barely able to touch the steering wheel,” said Professor Selover. “But, imagine what that would be like to a child trapped in a car seat. And once you introduce a person into these hot cars, they are exhaling humidity into the air. When there is more humidity in the air, a person can’t cool down by sweating because sweat won’t evaporate as quickly.”

It is not possible to predict exactly when a child’s core body temperature will rise above 104 degrees, which is heatstroke level, because individual factors such as clothing, health, and weight affect when heat becomes a fatal risk.

The researchers used data to model a hypothetical 2-year old boy’s body temperature. The team found that a child trapped in a hot car could reach a deadly core body temperature in about an hour if a car is parked in the sun, and just under two hours if the car is parked in the shade.

“We hope these findings can be leveraged for the awareness and prevention of pediatric vehicular heatstroke and the creation and adoption of in-vehicle technology to alert parents of forgotten children,” said study lead author Jennifer Vanos.

The research is published in the journal Temperature.

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By Chrissy Sexton, Earth.com Staff Writer