Dr. Ronald Herberman, director of the University of Pittsburgh Cancer Institute has warned his staff to limit mobile phone use, especially in the case of children.
His memo, sent to around 3,000 faculty staff according to the International Herald Tribune, outlined dangers he felt warranted highlighting, despite the lack of concern from other studies and institutions.
Herberman highlighted unpublished reports from a study, called Interphone, which involves scientists from 13 countries, mostly in Europe.
Although early results published show no cause from concern, he is worried about unpublished findings.
The director highlighted something he called a: "growing body of literature linking long-term cellphone use to possible adverse health effects including cancer."
"Although the evidence is still controversial, I am convinced that there are sufficient data to warrant issuing an advisory to share some precautionary advice on cellphone use," according to the document sent.
However, most other institutions and organisations are not concerned with the overall effect mobile phones have on the brain, including a large study in Denmark which tracked the number of tumours in mobile users over up to ten years, and found there was largely no cause for concern.