The World Health Organization's cancer research agency says mobile phones are "possibly carcinogenic".A review of evidence suggests an increased risk of a malignant type of brain cancer cannot be ruled out.However, any link is not certain - they concluded that it was "not clearly established that it does cause cancer in humans".A cancer charity said the evidence was too weak to draw strong conclusions from.Ed Yong, head of health information at Cancer Research UK, said: "The WHO's verdict means that there is some evidence linking mobile phones to cancer but it is too weak to draw strong conclusions from."The vast majority of existing studies have not found a link between phones and cancer, and if such a link exists, it is unlikely to be a large one."The risk of brain cancer is similar in people who use mobile phones compared to those who don't, and rates of this cancer have not gone up in recent years despite a dramatic rise in phone use during the 1980s."However, not enough is known to totally rule out a risk, and there has been very little research on the long-term effects of using phones."A group of 31 experts has been meeting in Lyon, France, to review human evidence coming from epidemiological studies.Source: BBC