More than a decade's use of mobile phones does not increase the risk of brain cancer, according to one of the largest studies yet conducted into the link.
The finding is reassuring in that, with long-term use of mobiles rising, there is no sign of increasing risk.
Worldwideuse of mobile phones is now so extensive, with more than one billion users round the globe, that concerns have grown about their possible health effects.
But the latest study of 420,000 users who had owned mobiles for up to 21 years has confirmed findings that there is no evidence of risk.
When in use, mobiles emit radio waves that can penetrate 4-6 centimetres into the human brain, raising fears they may trigger malignant changes in brain cells.
Studies have focused on tumours of the head and neck because of the localised exposure to radio waves. But only two among more than a score carried out have suggested an increased risk, and both of these have been criticised by other scientists for methodological flaws.
The latest study is a follow up to an earlier one, published in 2001, extending to an average of 8.5 years the period during which mobile users were monitored, with a maximum of 21 years.
It was carried out by researchers from the Danish Institute for Cancer Epidemiology and was funded by grants from the Danish Research Council and the Danish Cancer Society. There was no funding from mobile phone companies. The results are published in the US Journal of the National Cancer Institute.
Professor Tricia McKinney, Centre for Epidemiology and Biostatistics, University of Leeds, said: "The results of this Danish cohort study are important as they have analysed data from mobile phone company records and do not rely on users remembering for up to 10 years in the past how often they used their phone. The large numbers of subscribers in the study mean we can have some confidence in the results that have not linked mobile phone use to a risk of any cancer, including brain tumours."
