As more kids use mobile phones and surf the web at increasingly younger ages, sexting and Internet safety are becoming bigger childhood health concerns, edging out longtime worries like smoking and teen pregnancy, a new poll suggests.

Internet safety rose to become the fourth most commonly identified major problem in the 2015 C.S. Mott Children’s Hospital national poll on children’s health, up from eighth the year before, with 51 percent of adults this year citing it as a top concern.

Sexting, meanwhile, was cited by 45 percent of adults and advanced to number six on the list of most pressing problems this year, from 13th place in 2014.

“The public is well aware of the potential risks to children and teens of Internet activities and sexting, such as cyberbullying and predatory behavior,” poll director Dr. Matthew Davis of the University of Michigan in Ann Arbor said by email.

“Children’s use of the Internet continues to grow, so it makes sense that growing use, without much evidence of greater safety, would lead to higher levels of public concern,” he added.

Childhood obesity, bullying and drug abuse remained the top three concerns for the second year in a row, according to the survey of 1,982 adults age 18 and over conducted in May.

Smoking and tobacco use, usually rated near the top of the list, dropped from fourth to seventh place, which may reflect a declining number of children who have this habit, the researchers note.

School violence ranked number eight, followed by teen pregnancy and stress.

Many problems highlighted in the poll are health issues without clear cures, where some of the anxiety voiced by adults may be due to uncertainty about the best prevention or treatment options, Dr. Megan Moreno, of the Center for Child Health Behavior and Development at Seattle Children’s Hospital, said by email.

Some common issues such as asthma or diabetes may not make the list of top concerns because doctors and parents have a good idea how to address these conditions, said Moreno, who wasn’t involved in the poll. By contrast, parents, educators and health providers are still trying to determine the best approaches for obesity and Internet safety.

“This uncertainty about best practices likely compounds the worry that parents feel about how to protect their kids,” she said.

The top 10 health concerns in the poll also highlight a need for parents to foster open communication with children and teens and monitor not just their comings and goings but also their activities online, said Kathleen Davis, director of pediatric palliative care and ethics at the University of Kansas Hospital.

“Parents must take on a greater ‘hands on’ approach to parenting, knowing what their child is texting, emailing, snap chatting, facebooking and blogging and with whom they are communicating in those fashions,” Davis, who wasn’t involved in the poll, said by email.

While the new technologies may seem alien, the parenting strategies to deal with children’s online lives should be familiar, noted Lisa Jones, of the Crimes Against Children Research center at the University of New Hampshire.

“Striking the right balance with controlling technology use and access for children, or monitoring their behavior is something I think we are still figuring out and will probably be an ongoing process for parents, just like deciding how much to control what children choose to wear, who they can hang out with, and where they can go on their own,” Jones, who wasn’t involved in the poll, said by email.

“The key recommendation for parents is to keep communication open,” she said. “Make sure your children feel comfortable coming to talk to you when problems come up.”