With its 12.1-megapixel camera and sleek touchscreen, the Sony Ericsson Satio is one of the most desirable mobile phones you could buy this Christmas. You may recognise it from its high-profile advertising campaign: carefree twentysomethings bouncing on colourful spacehoppers. But one thing the advert fails to tell the viewer is that the Satio is one of the highest emitters of low-level radio waves on the mobile phone market.

Different models record different levels of radiation, and some experts want radio wave readings advertised as prominently as are the salt and fat content on food labelling. Professor Denis Henshaw, head of radiation research at the University of Bristol, says: “While we don’t have an advanced state of knowledge about the harmful effects of mobile phones, a number attached to a phone is at least a start in giving the consumer an informed choice.”

The reading is recorded as a specific absorption rate (SAR): the rate at which head tissue absorbs the phone’s radiation. The higher the reading, the more radiation is emitted. Nine years ago Henshaw advised the Stewart Report, the UK’s first committee to tackle the issue in depth. It failed to find concrete evidence of adverse effects, but it did recommend that radiation readings be displayed on the back of mobile phone boxes and as a menu option. (The Mobile Manufacturers Forum claims that it is “impractical” to put these figures on packaging, but they can usually be seen on the manufacturers’ websites.) The European guideline for maximum radiation exposure is 2W/kg in 10g of body tissue. The Satio’s reading is 1.58W/kg. The LG Crystal’s is 1.47W/kg. Samsung phones record consistently low SAR values, while the Apple iPhone 3GS is between the two extremes with 1.1W/kg. All these models fall safely within the guidelines, so should you worry about SAR? Perhaps yes, if the preliminary findings of the Interphone study, the biggest of its kind, are to be believed. It is conducted under the auspices of the World Health Organisation (WHO) and its conclusions will be drawn from research by scientists in 13 countries.

Some of the evidence from the 12 countries that have published their reports seems to suggest that there is “significantly increased risk” of developing some types of brain tumour if you use a phone for a decade or more. But this conflicts with the findings from other countries taking part in the study, including the UK; the WHO is expected to compile a definitive conclusion in the coming weeks. However, a US-Korean study in the Journal of Clinical Oncology last month concluded that there is possible evidence linking mobile phones to the risk of brain tumours.

Manufacturers do not appear to be ruffled by this. “Mobiles use radio frequency that has been studied extensively for 40 or 50 years,” says Michael Milligan, of the Mobile Manufacturers Forum. “There has been no research that has conclusively proved a link between guideline-level mobile phone use and brain tumours. SAR values are also not an indication of safety. They are the highest recordings in laboratory tests, but in reality your phone uses far less energy, particularly in an urban area with a good signal.”

Many experts also remain unconvinced. Professor Alan Preece, also of Bristol University, has studied radio frequency waves on human beings for the past ten years. He says: “Research is hindered by a lack of lifetime human case studies. Instead, theories have to be proven in laboratory animals, the evidence from which has so far been conflicting and confusing.” He says there is no biological reason why low-level radio waves should be carcinogenic. They have a heating effect that vibrates molecules but, unlike ionising radiation (such as X-rays), the structure of a molecule remains intact. Of course, the effect of low-level exposure over a lifetime has yet to be observed.

Nevertheless, many do worry. Alasdair Philips, of Powerwatch, a pressure group that researches the health effects of all electromagnetic waves, says: “SAR values are not the be-all and end-all. If you hold a phone loosely to your ear, the SAR will fall tenfold than if pressed tight to the ear.” Using hands-free headsets is even better, but Philips says: “I wouldn’t choose the highest-SAR phones. Given today’s technology, any reading above 1W/kg is unnecessary,” he says.

Meanwhile, Preece is so confident of phone safety that he has bought his ten-year-old granddaughter her first mobile phone. “I chose it by colour rather than by the SAR value,” he says. “It has thousands of times more value for a girl’s security and safety than it has deleterious effects.”

Highest radio wave levels

Sony Ericsson Satio (2009) 1.58W/kg LG Crystal GD900 (2009) 1.47W/kg Nokia 1661 (type RH-122) (2008) 1.38W/kg BlackBerry Bold 9700 (type RCM71UW) (2009) 1.36W/kg HTC Tattoo (2009) 1.25W/kg

Medium radio wave levels

Apple iPhone 3G S (2009) 1.1W/kg Nokia 6303 Classic (2009) 1.15W/kgLG Cookie KP500 (2008) 1.02W/kg Nokia 5800 XpressMusic (2009) 0.97W/kg Samsung Genio Touch (2009) 0.75W/kg Samsung Tocco Lite (2009) 0.54W/kg Samsung Jet (2009) 0.522W/kg

Lowest radio wave levels

Motorola Aura R1 (2008) 0.32W/kg BlackBerry 8700g (2006) 0.24W/kg Samsung SGH-F210 (2007) 0.2W/kg Samsung SGH-G800 (2007) 0.19W/kg Samsung SGH-X830 (2007) 0.119W/kg

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