Cordless phones are more of a health risk to young people than mobiles, according to new university research.
In a study of almost 400 Wellington, New Zealand, intermediate pupils, adjunct Victoria University researcher Mary Redmayne found pre-teens were more likely to suffer headaches if they made long or frequent calls on cordless phones or cellphones.
The research, to be published in the Environmental Health journal this week, also found high users of cordless phones more commonly experienced tinnitus, or ringing in their ears.
In a separate study, the PhD candidate discovered year 7 and 8 students talked on cordless phones for far longer than on their mobiles, meaning it was the home line exposing them to the highest doses of potentially harmful radiation.
"People are pretty poorly informed about how this technology works - many people don't realize that cordless phones are actually cellphones," Ms Redmayne said.
"Modern cellphones use the lowest amount of power that they need to transmit, but a cordless phone always works on full power."
Her population-adjusted research found a significant association between teens' radiofrequency exposure and short-term health issues - but international research suggested the long-term health risks were far more serious, she said.
"The highest category of use - over half an hour a day - in many studies has shown an increased risk of glioma, a malignant [brain or spine] tumor that is often fatal. Several studies have also shown an increased risk of acoustic neuroma - a little tumor on the nerve between the ear and the brain."
Other research papers showed male fertility was also adversely affected, this time from carrying a cellphone in a pants pocket. While many held that the science was inconclusive overall, Ms Redmayne said governments and individuals should be paying attention. "There was certainly enough to be concerned about."
Sophie Walker, of the National Centre for Radiation Science, who advises the Ministry of Health, said the latest research showed conclusively that radiofrequency radiation had an effect at the cellular level. "But it's very hard to say whether that translates into things like headaches or short-term effects people report . . . it's a very hard link to make."
The jury was also still out on long-term health effects. "Radiofrequency has only been used within the wider population for the last 30 years, so true long-term studies are really still under way. Really conclusive stuff hasn't yet been established."
But there was no doubt such a robust study showing irrefutable evidence that radiation had negative health effects would be taken seriously by scientists and governments. "It would have effects across the entire world."
Parents seeking to reduce their children's exposure to radiofrequency radiation from cell and cordless phones are advised to:
Choose a corded land line or a cordless phone with speaker-phone capabilities.
Keep the main transmitting base of the cordless phone away from bedrooms and desks.
Put children on text-only packages.
Advise children to avoid calls where reception is bad - when a mobile is far from a cell tower, it has to boost its signal to connect.
Talk to children about usage and choosing times where they decide to be unavailable, such as switching their phones off - or simply to flight mode - from a certain hour at night.