The number of such injuries has more than doubled since 2005, even though the total number of pedestrian injuries dropped during that time. And researchers believe that the actual number of injured pedestrians is actually much higher than these results suggest.

"If current trends continue, I wouldn't be surprised if the number of injuries to pedestrians caused by cell phones doubles again between 2010 and 2015," said Jack Nasar, co-author of the study and professor of city and regional planning at The Ohio State University.

"The role of cell phones in distracted driving injuries and deaths gets a lot of attention and rightly so, but we need to also consider the danger cell phone use poses to pedestrians."

The study found that young people aged 16 to 25 were most likely to be injured as distracted pedestrians, and most were hurt while talking rather than texting.

Nasar conducted the study with Derek Troyer, a former graduate student at Ohio State. It appears in the August 2013 issue of the journal Accident Analysis and Prevention.

The researchers used data from the National Electronic Injury Surveillance System, a database maintained by the U.S. Consumer Products Safety Commission (CPSC), which samples injury reports from 100 hospitals around the country. These reports are used to estimate total injury occurrences at emergency rooms across the country.

They examined data for seven years (from 2004 to 2010) involving injuries related to cell phone use for pedestrians in public areas (in other words, not at home).

A wide variety of injuries were reported. One 14-year-old boy walking down a road while talking on a cell phone fell 6 to 8 feet off a bridge into a rock-strewn ditch, suffering chest and shoulder injuries. A 23-year-old man was struck by a car while walking on the middle line of a road and talking on a cell phone, injuring his hip.

Findings showed that in 2004, an estimated 559 pedestrians were treated in emergency rooms for injuries received while using a cell phone. That number dropped to 256 in 2005, but has risen every year since then. Meanwhile, the total number of pedestrians estimated to be treated in emergency rooms dropped from 97,000 in 2004 to 41,000 in 2010.

Nasar said he believes the number of injuries to distracted pedestrians is actually much higher than these statistics suggest.

He said a more accurate count of injuries to walkers might come from comparing distracted walking to distracted driving, which has been much more heavily studied.

Nasar compared CPSC estimates for injuries related to drivers distracted by cell phones with actual data from emergency rooms across the country. Recent research examining increases in traffic accidents related to cell phone use suggests that the number of crash-related injuries in emergency rooms is actually about 1,300 times higher than CPSC national estimates, Nasar said.

Such data isn't available to compare CPSC estimates with actual injuries to distracted pedestrians. But if the pedestrian numbers are similar to those for drivers, then there may have been about 2 million pedestrian injuries related to mobile phone use in 2010.

Moreover, Nasar said he believes emergency room numbers underestimate actual injuries because not every person who is injured goes to an emergency room. Uninsured people might not go at all. Other people might take care of themselves, or go to an urgent care center. In addition, not everyone who does go to an emergency room reports using a cell phone.

"It is impossible to say whether 2 million distracted pedestrians are really injured each year. But I think it is safe to say that the numbers we have are much lower than what is really happening," Nasar said.

As might be expected, young people are the most likely to be injured by distracted walking. The 21- to 25-year-old age group led the way, with 1,003 total injuries during the seven years covered by this study. The 16- to 20-year-olds were not far behind, with 985 total injuries.

For pedestrians, talking on the phone accounted for about 69 percent of injuries, compared to texting, which accounted for about 9 percent.

Nasar said he doesn't think the lower texting injury rate is because texting is necessarily safer than talking and walking. Instead, it is probably because fewer people actually text while walking than talk while on foot.

The problem with distracted pedestrians is likely to get worse, he said.

"As more people get cell phones and spend more time using them, the number of injuries is likely to increase as well. Now people are playing games and using social media on their phones too," he said.

Nasar said he believes the best way to reverse these numbers is to start changing norms for cell phone use in our society. And that starts with parents.

"Parents already teach their children to look both ways when crossing the street. They should also teach them to put away their cell phone when walking, particularly when crossing a street."