I've never felt safe putting a phone near my head.

We have a brain surgeon in Australia who's been saying that mobiles phones are dangerous for years. A lot of his patients with brain tumours tell him they have held their mobile phone on the side where tumour regularly.
http://www.news.com.au/technology/brain-surgeon-dr-charlie-teo-warns-against-mobiles-home-appliances/news-story/a44c78d3671c38971f87687b990b34cf