A broken wrist from climbing a tree, or a blistering sunburn from a day at the beach — these used to be parents' chief health concerns in the summer.

Now we can all add hearing loss, eye strain or perhaps even "Blackberry thumb" to our worry inventories. Those are just some of the potential physical impacts of our kids spending too many idle summer days listening to headphones set at a deafening volume, squinting at tiny, overly bright screens, or running fingers across a keypad in a constant, repetitive motion.

The sweeping social impact of the electronic revolution that has occurred in the past generation is much debated and dissected, but more and more we are being warned of the potential physical toll that our kids' digital toys can take on their bodies.

Can our kids really get brain cancer from spending too much time with a cellphone next to their ear, or can a young boy become sterile by carrying it in his pants pocket day after day? Will our generation of digital natives — as today's kids are often called — suffer future health impacts that health authorities can only speculate about today?

The medical authorities can offer definitive conclusions on some of these new worries — yes, kids can and have suffered hearing loss from exposure to high-volume headphones, and yes, any type of repetitive muscle movements can cause tendonitis or other stress injuries to the hands and fingers, including the thumbs.

"At the top of the list of what parents ought to be concerned about is certainly hearing loss from headphones, particularly ones that go in the ear," said Dr. Stephen J. Thompson, chief of pediatric neurology at Hackensack University Medical Center.

Computer-related eye strain and repetitive stress injuries of the hands, fingers and thumbs are also real phenomena, although often cured by simply taking a break from the technology.

Lowest on Thompson's list of worries would be exposure to the low-level radiation in cellphones since studies are not conclusive on whether there is an increased risk of cancer or a definite link to other health impacts.

"There's still a lot of research that still has to be done on this subject," Thompson said.

Perhaps the best thing that parents can do to assuage their fears about the health dangers that future studies might reveal is to enforce moderation.

"The real concern should be over excessive use," Thompson said. "Parents should be teaching kids to exercise common sense and to use the technology in an appropriate way."

If parents are worried about the radiation in cellphones, a simple solution is to make sure the phones aren't turned on all the time and aren't next to their kids' bodies every minute of the day, Thompson advised.

While seeing a report about a cancer link to cellphones might cause some parents to gasp, David Walsh, a psychologist and author who writes about the impact of electronic media on family life, thinks most parents pay too little attention to two other childhood conditions that can be more definitely linked to overuse of digital technology: sleep deprivation and obesity.

"Those are the physical impacts about which there isn't any doubt," Walsh said. "Yet to most parents they probably just seem like vague concerns. They're not as dramatic as cancer."

E-mail: diskin@northjersey.com

The possible dangers:

Brain cancer

• Concern: Fears were stoked in May when the World Health Organization declared the microwave-level radiation emitted by cellphones a "possible carcinogenic." Other medical authorities say there is no evidence of a direct causal link to brain cancer.
• Advice: If you want to be on the safe side, consider buying a head set rather than having your child hold the phone up to his ear – and next to his brain.

Hearing loss

• Concern: An estimated 12.5 percent of children age 6 to 19 suffer from noise-induced hearing loss.
• Advice: The Children’s Hearing Institute recommends a time limit of one hour a day with the volume of headphones set to 60 percent of the device’s maximum level. If children listen for longer periods, the volume level should be much lower and never turned up to drown out surrounding noise.

Eye strain

• Concern: Staring at a screen for too long hasn’t been shown to cause permanent eye damage, but it can tire and dry out the eyes.
• Advice: Rest and saline drops can be the cure. Prevention techniques recommended by the American Academy of Ophthalmology are to remain at least 25 inches from the screen and to reduce the brightness level of the screen and make sure there’s enough light in the room. Also remember to make yourself blink and to a take a break from the screen every 20 minutes to look at something at least 20 feet away for at least 20 seconds – what’s called the 20-20-20 rule.

Blackberry thumb

• Concern: The umbrella medical term is repetitive stress injury, and there are a variety of ways the hands and the digits can be taxed by overuse of technology.
• Advice: Pain is the first indicator of a problem so if you feel any in the fingers and hands, stop texting or typing. Experts recommend taking frequent breaks, sitting in an ergonomically correct position and trying to hold the device with a "neutral grip," meaning the wrist is straight and not bent too strongly in one direction.

Infertility

• Concern: There has been some early study of the claim that boys and men who carry cellphones in their pockets run the risk of exposing their sperm to radiation that decreases its viability and motility. But none of the major health authorities have considered the evidence conclusive.
• Advice: If you’re worried, tell your son to keep the phone turned off if he carries it in his pocket, which reduces the amount of radiation emitted. Or keep it in the backpack.

— Colleen Diskin