The Home Office has commissioned research into possible health risks posed to the emergency services by the controversial Tetra radio system in vehicles.
It has asked Microwave Consultants (MCL) to conduct a study of how absorption rates of the radio waves emitted from Tetra handsets vary inside vehicles. Fears have been raised that vehicles could act as 'Faraday cages', increasing exposure.
A spokesman for the Police Federation told vnunet.com that it still had "serious concerns" over the safety of Tetra.
"We have reservations about having a system before the full results of the long-term health effects are known," he said.
But the Home Office is keen to play down fears, arguing that the tests form part of ongoing research that will reinforce its assertion that Tetra is safe.
The National Radialogical Protection Board's independent advisory group had already concluded "it was unlikely that Tetra could pose a risk to health", said a spokeswoman for the Home Office.
"Preliminary tests indicate that there are no significant hot spots due to multiple reflections inside cars," she added.
MCL will use robot-controlled probes to measure Tetra signal strengths within vehicles.
But opponents of Tetra remain adamant that Home Office tests are ignoring the health risks.
"Their research has focused on the heat effects of Tetra. It is actually the frequency that is the major concern," said Lynne Edmunds, joint co-ordinator of pressure group Mast Action UK (MAUK).
"Unless they change the frequency, Tetra will never be safe."
According to Edmunds, MAUK has received hundreds of reports from police officers complaining of illness after using Tetra equipment. Symptoms range from severe migraines and sleeplessness to depression.
The Tetra system uses radio frequencies operating at 17.6Hz, close to the 16Hz frequency at which the brain operates.
But the Home Office has dismissed the concerns.
"There is no evidence that the 17.6Hz modulation in the signal from Tetra handsets has any interaction with the brain," said the Home Office spokeswoman.
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