WASHINGTON - Can a parent imagine something worse than the death of a child? Perhaps only the thought that it might have been prevented.

Each year in the U.S. about 12,200 people younger than 19 die of unintentional injuries. Around the world, fatal injuries in children total 830,000 a year, a number roughly equal to all the children in Chicago. That's 2,270 a day, of which at least 1,000 could have been prevented, experts say.

This huge toll of heartbreaking death sits atop a pyramid of nonfatal injury. In the U.S., 9.2 million children visit the emergency room each year for unintentional injuries. Globally, about 690 children miss school or work, or go to the hospital, for every child accidentally killed.

Public health authorities are lifting the curtain on childhood injury. The Centers for Disease Control and Prevention in December released an atlas and 114-page report on childhood injury. Simultaneously, the World Health Organization published a detailed report on the subject.

American parents are notorious worriers. But the chance of their child dying of an unintentional injury is one-third that of children worldwide, and one-quarter that in Africa and the Middle East, the most child-dangerous regions.

Although the overall risk is relatively low, 44 percent of all deaths between ages 1 and 19 in this country are caused by injuries. The new reports show parents and policy-makers where they might choose to focus their worries and efforts, from finding safe places for infants to sleep to being sticklers for the rules when teenagers get into cars.

"It is a huge public health concern, and I don't think we pay as much attention to it as we should," said Julie Gilchrist, a physician and epidemiologist at CDC and one of the authors of the report.

(By the way, you won't hear Gilchrist or her colleagues use the word "accidents." That word, they say, implies that the events could not have been avoided and the damage could not have been prevented - exactly the opposite message they want to convey.)

"Unintentional injury" excludes homicide and suicide but captures all other categories of traumatic event. Childhood injuries cost the nation about $300 billion a year. The CDC's report sketches a picture of risk and vulnerability that differs by age, sex, ethnicity, locale and economic status.

In perhaps the most dramatic example of variation, suffocation causes 66 percent of deaths of children younger than 1 but is only a single-digit cause for all other children. Two-thirds of suffocation deaths in infants occur in bed, and only 7 percent are the result of choking on food or foreign objects. But in children past their first birthday, 7 percent of suffocation deaths occur in bed and slightly more than one-third are by choking. In the first five years of this decade, 3,868 children younger than 1 died of suffocation, compared with 1,866 over that age.

For all children older than 1, motor-vehicle-related injuries are the leading cause of unintentional death. But even in that group, much changes by age.

Rates of death in car crashes are largely unchanged from birth until a child reaches the 15-to-19 age group, when they jump sixfold. The rate of bicycle deaths is highest for those ages 10 to 14, followed by the 15-to-19 group and then 5 to 9 year olds. Pedestrian deaths are slightly higher in 1 to 4 year olds than in 15 to 19 year olds. All other ages are much lower.

Perhaps not surprisingly, age itself is a risk for injury. Of the 73,000 children who died from 2000 to 2005, 40,000 were 15 or older, 56 percent of the total.

Sex is a risk factor, too.

The overall annual death rate for boys is 19 per 100,000 population ("population" in this case being children of the same age group). For girls, it is just 10 per 100,000. Sex and age combine to produce a death rate of 45 per 100,000 among boys ages 15 to 19.

In motor vehicle deaths, the risk that comes with age reflects numerous behaviors and vulnerabilities.

For example, about 90 percent of infants who are fatally injured are in some sort of special seat or restraint (although not always properly used). As soon as a child is able to exert willpower, risk goes up. Of children 4 and younger who are killed, 30 percent are unrestrained. Of teen-agers killed, more than half are not wearing seat belts. (Only 47 percent of students report always wearing seat belts when riding with others, compared with 82 percent of adults.)

The high teen death rate from car crashes also reflects the inexperience and immaturity of new drivers.

Speeding and night driving are more potent risk factors for teens than for adults, as is the presence of passengers. The fatal crash risk for 16 and 17 year olds is three times as high at night as during the day. For every person who gets in a car with a teen driver, the risk of a crash increases, until with three or more passengers it is four times as high as if the teen were driving alone.

That "dose-response" effect presumably reflects distractibility of the driver. Curiously, it's exactly the opposite of what's seen in adults. As they add passengers, their trips get safer.

Cellphones and text messaging are potent new sources of distraction, but how they stack up in the hierarchy of hazards is unknown.

"We are just beginning to look at those factors. We know that any kind of distraction is contributing to crashes in teens," said Arlene Greenspan, an epidemiologist at the CDC's National Center for Injury Prevention and Control.

But in many ways the most provocative and perplexing variable in a child's risk is where he or she lives.

In this decade, the rate of fatal injury in children has varied fourfold among the states, from 7 per 100,000 in Massachusetts to 29 per 100,000 in Mississippi. Seemingly disparate clusters of states, however, tend to show up over and over in many age categories and causes of death.

These include a cluster of mid-South states (Mississippi, Arkansas and Louisiana); upper Great Plains states (the Dakotas and Montana); and two outliers (Alaska and, for transportation-related deaths, West Virginia).

Many variables are in play in these places, with poverty and rural residence probably the most important ones. In Alaska and the northern Plains, the high rates may also reflect the presence of many Indians and Alaska natives, whose children have twice the death rate as American children overall (30 per 100,000 vs. 15 per 100,000).

"About half of all American Indians live in a rural environment," said David Wallace, an injury prevention specialist at CDC. "Driving on rural roads has a higher fatality rate than driving in a city. There are problems with speed and inattention, and if you compound that with alcohol you get a high fatality rate."