As cell phone use becomes common place among children, parents express growing concerns about the content and quantity of material transmitted via the devices. One major concern is "sexting," in which sexually explicit material is shared via text messages, photos or video transmitted between cell phones.

A report released today by the C.S. Mott Children’s Hospital National Poll on Children’s Health shows that 41 percent of parents are either “very” concerned or “somewhat” concerned with the amount of time their children spend text messaging.

The poll also shows that 27 percent of pre-teens, ages 9 - 12, and 75 percent of teens, ages 13 - 17, have their own cell phones. Among these children, 87 percent send and receive text messages and 23 percent access the Internet through their phones. “We found that 55 percent of parents guard against inappropriate cell phone activity by limiting the time children can use their cell phone,” says Matthew Davis, M.D., director of the poll and associate professor of general pediatrics and internal medicine at the U-M Medical School. “Time limits are used substantially more often by parents of preteens than by parents of teens.”

However, a less common strategy, used by 33 percent of parents, involves blocking the transmission of images on children’s cell phones. The poll found that 45 percent of parents block images on phones for pre-teens, while only 29 percent for teens.

“While many parents have placed limits related to time spent using cell phones, far fewer parents have instituted a mechanism for blocking images,” says Davis, who is also associate professor of pediatrics and internal medicine in the U-M Medical School and associate professor of public policy at the Gerald R. Ford School of Public Policy. “Parents may not be aware of the various options for blocking inappropriate content or the potential risks of sexting.”

As parents and relatives consider purchasing cell phones as holiday gifts for kids, it may be wise to consider adding image blocking safeguards to calling plans. In addition, parents should establish rules and expectations with their teens and preteens, in order to guard against sexting, Davis says.

For parents not already doing so, most national cell phone companies will block image content for a monthly fee (usually $5-$10).