Heavy mobile phone use may be linked to an increased risk of cancer of the salivary gland, a study suggests. Those who had used the phone against one side of the head for several hours a day were 50% more likely to have developed a salivary gland tumor. Cancer of the salivary gland is a very rare condition anywhere in the world. Dr Siegal Sadetzki, who led the research, said that while mobile phone use in Israel was much heavier than in many other parts of the world, this gave an insight into what the long-term, cumulative impact could be.