The inside of a car parked in the sun can get hot enough to kill a child in as little as one hour, and parking in the shade doesn't even buy another full 60 minutes, according to new research from Arizona State University published in the journal Temperature.
"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 Nancy Selover, an Arizona State climatologist and research professor in a news release.
The scientists wanted to test how hot different cars would get based on where they were parked on a hot day. To do so, the researchers parked two identical silver mid-size sedans, two identical silver economy cars, and two identical silver minivans outside in Tempe, Ariz., when the temperature was over 100 degrees.
"These tests replicated what might happen during a shopping trip," Selover said in the news release. "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. "
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The researchers discovered that the dashboard of the car parked in the sun hit an average of 157 degrees after an hour, hot enough to fry an egg. The seats hit 123 degrees, the steering wheel 127 degrees, and the inside temperature 116 degrees.
"I knew the temperatures would be hot, but I was surprised by the surface temperatures," Selover said.
The results weren't quite as extreme in the shade, but they were still potentially deadly. After an hour, the dashboard hit 118 degrees and the interior was around 100 degrees. Bigger cars took longer to heat up than smaller cars.
"We've all gone back to our cars on hot days and have been barely able to touch the steering wheel," Selover said in the news release. "But, imagine what that would be like to a child trapped in a car seat."
It's not the temperature alone that can kill, either — it's the humidity, which can prevent the body from cooling itself down.
" 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," Selover wrote.
The deaths and heat injuries begin when a child's core body temperature rises above 104 degrees and stays there, wrote Jennifer Vanos, the study's lead author.
The researchers found that a hypothetical 2-year-old's body could hit that temperature in an hour in a car parked in the sun and in less than two hours in a car parked in the shade.
Vanos wrote that she hoped the findings would prompt adoption of more "in-vehicle technology" to alert parents when they accidentally leave children behind, something another researcher named Gene Brewer wrote could happen to anyone.
""Often these stories involve a distracted parent," he said. "Memory failures are remarkably powerful, and they happen to everyone.
There is no difference between gender, class, personality, race or other traits. Functionally, there isn't much of a difference between forgetting your keys and forgetting your child in the car," Brewer, a psychology professor at Arizona State, wrote in a news release.
Nearly 750 children have died of heatstroke in the U.S. since 1998, according to NoHeatStroke.org. At least seven have already occurred in 2018, reports NoHeatStroke.org, including the deaths of two five-month-old twins in Virginia in early May and the death of a 1-year-old girl in Nashville Wednesday evening.