In a careful and detailed essay in the New York Times, assistant professor of medicine in the medical oncology division at Columbia University, and author, (right)  Siddhartha Mukherje writes a careful amd intriguing study into this issue and says as yet for the cellphone, the evidence is far from convincing.

"The word “radiation” refers to energy that emanates from a source — but the spectrum of radiant energy is broad," he writes. "On the highly energetic end of the spectrum is ionizing radiation — like X-rays or cosmic rays — that are so powerful they can tear away electrons from atoms and molecules and penetrate barriers like the skull and the brain. On the way into — and through — the body, they deposit powerful bursts of energy, generate corrosive chemicals, ruffle up DNA, kill cells and, most notably, mutate growth-controlling genes to cause cancer.

"Nonionizing radiation lies on the other end of the energy spectrum. These rays can warm cells, boil water and stimulate chemical reactions, but they cannot strip electrons away from atoms or damage DNA. They have no capacity to mutate genes directly and thereby no simple and direct means of initiating cancer. Radiation from microwaves, from cellular phones and from light bulbs are examples of nonionizing radiation.

"All of this makes cellphone radiation a relatively unlikely culprit as a mutation-causing agent.Cellphones and their radiation have been tested for many of these properties — for instance, their ability to chemically modify DNA without causing mutations — but evidence linking this form of radiation to such cellular changes remains largely negative.

"What is clearly needed, experts agree, is a single, definitive, unbiased study — “one trial,” to borrow Paget’s terminology. Logistically speaking, the simplest such human trial is a case-control study that compares cancer patients with healthy patients, using phone-log data that companies have thus far been reluctant to provide.

The simplest animal study involves subjecting rats and mice to long-term exposure to cellphone radiation. The National Toxicology Program has begun such a study. Cellphone radiation will be turned on and off for 10-minute stretches for 20 hours each day. This experiment — the closest we will get to making mice use actual cellphones — is likely to be published in 2014." he notes.

Laptop fertility threats?
So how convincing then are reports on the studies in the Fertility & Sterility Journal by the State University of New York that for men, just sitting with a laptop in your lap, thighs together to balance it, will find that scrotal temperatures rise by 2.1^oC.

"Until further studies provide more information on this type of thermal exposure, teenage boys and young men may consider limiting their use of laptop computers on their laps," said Dr Yefim Sheynkin.

Speaking on behalf of the British Fertility Society, Dr Allan Pacey, senior lecturer in Andrology at the University of Sheffield, said: "Further work is needed to see if regular laptop use is a risk factor in male fertility."

Cooling off for certainty
For those who would like to take the pragmatic approach, the Personal Cooling Centre which offer a Mini Chillow for those who like their pillows cool (rrp £19.95) can now provide that vital  cooling pad that will absorb heat from the laptop and lower the temperature of your lap.

Simply filled with 1.25litres of tap water, absorbed into the internal foam core, and activated, it remains cool and ready for use. At 2cms thick it is comfortably light and thin to have in your lap.

For the scientists, it's back to practical trials, obliging mice and powerfully hot scientific computing.