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New Warning On Mobile Phones
Mobile phone users should keep handsets away from their bodies while waiting for a call, university researchers say.
Research has shown that radiation emission is greatest during this phase, according to a study at Hong Kong University.
The researchers also advise pregnant women and young people to keep their use of mobile phones to a minimum.
The findings have emerged from a study by the university's Radio-isotope Unit.
Unit director Tso Wong Man-yin said radiation emissions were checked during five phases - connecting, ringing, answering, listening and connected, but not talking.
Five randomly-chosen models were tested. They included a new miniature model, a hands-free model, a non-hands-free model, a model with a pull-out antenna and a model with a fixed antenna.
An additional test was made with a device attached to the antenna to reduce the effect of the electromagnetic field.
The results consistently showed the highest radiation during call time.
The amount of radiation in this phase ranged from 5.5 micro-watts per square metre to more than 10 micro-watts, which was 20 times the amount released when ringing and listening. Even when the phone was not in operation, the figure was 0.05.
The results also showed that hands-free devices did not reduce radiation significantly. Nor did the device attached to the antenna.
Professor Tso Wan-wai, of the university's biochemistry department, said there was no evidence that emissions were high enough to be harmful.
But Prof Tso suggested that users put their mobile phones a distance from their bodies until a connection is made.
"Maybe we should change the way we use mobile phones," he said.
He also suggested users should not talk for long periods or hang the phone on their chests, particularly pregnant women whose unborn babies could be vulnerable to radiation.
"Radiation may cause negative effects to reproductive cells. Pregnant women and young people are subject to a higher risk in this respect," Prof Tso said.