According to the Kansas-based organization Kids and Cars, 48 children have died of hyperthermia after being left or becoming trapped in a hot car or truck. The previous record of 47 was set in 2005, says Janette Fennell, the group's founder and president.
"I'm devastated," Fennell said Wednesday.
The latest death was a 2½-month-old girl who died Sept. 20 in Kingman, Ariz., after being left five hours in a car in 100-degree heat. Police say the girl's father forgot the baby was in the car, went inside the house and took a shower and nap.
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Fennell had waited until the results of an autopsy on two Kentucky brothers before declaring this a record year. The two boys, ages 4 and 6, died Aug. 6 after apparently climbing into their family's pickup truck, but the cause of death was not released until this week, Kentucky State Police Detective Scott Skaggs said Wednesday.
"Everything looks like right now that they got in the car themselves," Skaggs said. No charges have been filed in the case.
Jan Null, an adjunct professor of meteorology at San Francisco State University who also tracks these deaths, said it's hard to say why deaths spiked this year; there were just 33 deaths in 2009, which also was a hot year. He noted that the Kentucky deaths did not occur on a record hot day.
"I think from the small 13-year sample that we have that probably from a statistical basis, this is within the range of what you would expect," he said. "It's impossible, I think, to associate it with the weather totally. Is weather a factor? It's always a factor."
Since 1998, an average of 37 children have died in the United States after being left in or becoming trapped in a hot vehicle. According to Fennell's statistics, Texas leads the nation with 13 deaths, followed by Florida with 5, and Arizona, Georgia, Kentucky, Ohio and Tennessee with three each.
Fall has officially begun, but that doesn't mean the end of hot weather - or of danger. Fennell has recorded hot-car deaths as late as December, and in every month except January. There were three car-related hyperthermia deaths in November of 2006, and four in October of 2008.
And they don't just occur in the so-called hot states of the South and West. This year, children have died in hot cars in as far north as Maine, Wisconsin and South Dakota.
"My biggest worry is that we might break 50 this year," said Fennell. "And that's too much to think about."
Such deaths have spiked since the 1990s, when laws began requiring that infants be strapped into rear-facing car seats in the back seats of vehicles to avoid air-bag injuries. Fennell said more than 40 percent of the children who died this way are less than a year old.
An Associated Press investigation in 2007 found that criminal charges are filed in about half of these cases. Experts say leaving a child in a hot car is not always a sign of negligence, but is often the result of a distracted or sleep-deprived brain, or a sudden change in routine.
Fennell and others recommend putting a cell phone, purse, briefcase or other item beside the car seat as a way of forcing the driver to remember there is a child in the vehicle. Her group and others have also been calling for regulations requiring automobile manufacturers to install alarms that would tell them when a child was left behind.
"We've been doing this for over a decade, trying so hard to get the word out and educate people about this issue," said Fennell. "It just shows that even with education, this is not getting any better. And it points to the need for some technology to help us prevent these most preventable deaths."