The United Kingdom, Germany, Belgium, Israel, Russia and India advise that children limit their cellphone use. (AP)

Close to a dozen countries around the world have issued warnings or cautions about children using cellphones, but Health Canada has no similar message for Canadians.

France is about to make it illegal to market cellphones to children under 12. The United Kingdom, Germany, Belgium, Israel, Russia and India are also advising children limit their use of cellphones.

Finland's Radiation and Nuclear Safety Authority encourages parents to err on the side of caution, saying radiation from cellphones could pose a health risk but the research into possible effects of prolonged cellphone use is unclear. In Russia, it’s recommended children under 18 not use cellphones at all.

But while a survey conducted by CBC-TV's Marketplace on more than 1,000 Canadian children found almost half of nine- to 13-year-olds now have cellphones, Health Canada gives no such advice about the risks of cellphone use.

'The brain of a child literally is less dense, it's more porous, it's more susceptible to everything.'— Devra Davis, professor of epidemiology

"There is no convincing evidence of increased risk of disease from exposure to radio frequency electromagnetic energy from cellphones," Health Canada said in an email sent to Marketplace. "It is up to each person to decide if they can live with the possibility of an unknown risk from cellphone use."

The agency did offer a warning about other risks associated with using a cellphone.

"Personal safety issues that should be taken into consideration in the use of cellphones by children primarily involve concentration. For example, similar to adults not using a cellphone while driving, children should not use them while riding bicycles," Health Canada wrote.

The Canadian Wireless Telecommunications Authority, an industry group, follows Health Canada's recommendations on cellphone use.

"These countries for the most part have come up with precautionary measures without stating that there is any evidence in their view that links this to any significant danger," said Bernard Lord, the former premier of New Brunswick who now heads the authority.

Opinion among scientists on research into the health effects of cellphone use are so divided, a United Nations agency that has been investigating whether radiation from cellphones could lead to cancer in adults has been unable to release its study.

The International Agency for Research on Cancer, a UN watchdog, was supposed to release the study, known as Interphone, three years ago. It hasn't yet been published because the scientists are divided over parts of the study — particularly over research that suggests long-term users of cellphones are more likely to develop brain cancer.

Knowledge gap significant: epidemiology professor

Devra Davis, a professor of epidemiology and the director of the Centre for Environmental Oncology at the University of Pittsburgh Cancer Institute, believes the knowledge gap in the scientific literature is enough reason to keep phones away from kids.

"Because the latency between exposure and brain cancer could be 20 or 30 years … we are basically treating ourselves like lab rats in an experiment without any controls," said Davis.

The brains of adults and children differ when it comes to how they absorb the radiation that cellphones emit, Davis added.

"The brain of a child literally is less dense, it's more porous, it's more susceptible to everything," she said.

Adult brains are thicker and denser, so the radio frequency signal is absorbed less deeply, she said.

The low-level radiation emitted by a cellphone is absorbed more than halfway through the brain of a five-year-old, Davis said.

Interphone author and epidemiologist Elisabeth Cardis is planning another study to be done specifically on children.

"If there's a risk, it's likely going to be higher because of the usage and because of the innate sensitivity of children," Cardis said. "So I think it's very, very important that we study this so urgently."

Marketplace airs Friday nights at 8:30 p.m.