No there is no link between it. You would think that with more people using cell phones the presence of brain tumors would have gone up as well. they did statistics on brain tumors over the past 10 years and found no link between cell phones and brain tumors.
If you mainly use texting them the phone won't be by your head,its the Radiofrequency (RF) Radiation that is said to cause the proublem.So tell him to get rid of that microwave cause most people stand infront of it waiting for food to cook/heat up.
Probably the most important use for RF energy is in providing telecommunications services. Radio and television broadcasting, cellular telephones, radio communications for police and fire departments, amateur radio, microwave point-to-point links, and satellite communications are just a few of the many telecommunications applications. Microwave ovens are a good example of a noncommunication use of RF energy. Other important noncommunication uses of RF energy are radar and for industrial heating and sealing. Radar is a valuable tool used in many applications from traffic enforcement to air traffic control and military applications. Industrial heaters and sealers generate RF radiation that rapidly heats the material being processed in the same way that a microwave oven cooks food. These devices have many uses in industry, including molding plastic materials, gluing wood products, sealing items such as shoes and pocketbooks, and processing food products. http://www.hps.org/hpspublications/articles/rfradiation.html