In 2011, the International Agency for Research on Cancer (part of the World Health Organisation) classified radiofrequency electromagnetic fields ('microwave emissions'), such as those emitted by mobile phones, as possibly carcinogenic to humans (IARC Group 2B). This classification was based on an increased risk for glioma, a malignant type of brain cancer, associated with mobile phone use.
This classification means that there may be an increased risk of cancer associated with mobile phone use, especially for people who use the phone for long periods of time (30 minutes or more) each day. However, evidence is still limited at this stage and further research is required.
Due to the possible health risk, it is prudent to limit exposure to microwave emissions from mobile phone use where practical.