LONDON, ENGLAND - A major decade-long study, overseen by the World Health Organization (WHO) and costing £20 million (S$45.8 million), has found a link between heavy usage of cellphones and brain cancer.

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The Daily Telegraph newspaper reported that a preliminary breakdown of the study's results, without being definitive, found a "significantly increased risk" of some brain tumours tied to cellphone usage of 10 years or more.

The head of the study said she backed fresh warnings, including restricting the use of cellphones by children.

The Interphone investigation by WHO, the public-health arm of the United Nations, involved research in 13 nations. Some 12,800 people were surveyed between 2000 and 2004, with tumour sufferers and healthy people interviewed to see if their cellphone usage patterns differed.

The publication of the final paper, funded partially by the cellphone industry, has been delayed by friction among its authors over how the findings should be presented.

Earlier studies on the impact of cellphone usage have not been conclusive.

The Telegraph quoted a spokesman for Britain's Mobile Operators Association as noting that over 30 scientific reviews had found no adverse health effects, while a spokesman for the country's Health Protection Agency stated that there was "no hard evidence at present" of a health hazard.

However, he backed limiting "non-essential" use of cellphones by children.

The Telegraph report also cited an Israeli study which concluded that heavy cellphone users were 50 per cent more likely to come down with tumours of the parotid salivary gland.