In the largest study of mobile phone use, Danish researchers concluded mobile phone use does not increase risks of tumours of the central nervous system, providing little evidence for a causal association. Scientists from the Institute of Cancer Epidemiology in Copenhagen looked at people aged at least 30 who subscribed to mobile phone contracts and compared their rates of brain tumors with non-subscribers between 1990 and 2007. More than 350,000 people were involved in the study.

At the end of May, the World Health Organization's International Agency for Research on Cancer decided cellphone use should be classified as "possibly carcinogenic to humans."

A month later, the International Commission on Non-Ionizing Radiation Protection's committee on epidemiology said the scientific evidence increasingly pointed away from a link between mobile phone use and brain tumors.