If you use your mobile phone for more than 16 minutes a day you are damaging your cells, including your DNA, which could lead to an increased cancer risk. Research from Tel Aviv University in Israel showed considerable oxidative stress in the saliva of heavy mobile phone users compared to deaf users’ saliva who obviously used their phones exclusively for texting. Dr. Yaniv Hamzany noted that oxidative stress, caused by radiation from the phone, is linked to cell mutations, which could lead to the development of cancerous tumours.
So use a landline or text and only talk on your mobile, if necessary, for very short periods. The damage risk to young people is even greater so limit mobile use even more for under 18s (if you can!).