The second camp is companies -- and this means colleagues and immediate bosses, not just senior management. Companies need to accord a greater amount of respect to employees' right to personal time. Ideally they should define a corporate policy on out-of-hours calls, and ensure staff sticks to it. Not only will a responsible, respectful policy on mobile phone use keep employees happier and more motivated, it will ultimately translate into greater efficiencies, since staff that doesn't fear constant interruptions are more likely to make them available to deal with a real emergency.

While evidence remains inconclusive, there remain concerns about the frequent use of mobile phones on human health. The potential impact of the kind of electromagnetic fields generated by cellular phones on the human brain has received little attention until relatively recently, and it's probably still much too soon to pronounce on the possible adverse effects of long-term exposure.

The little, and inconclusive, research undertaken so far has nonetheless hinted that excessive exposure to electromagnetic fields (EMF) could cause such undesirable effects as memory loss, Parkinson's and Alzheimer's diseases, and even brain tumors.

An Australian study published in 1997, for example, suggested that transgenic mice exposed to signals similar to those emitted by a cellular phone were up to twice as likely to develop lymphomas. A UK study, meanwhile, found that mobile phone use could affect the nerve cells responsible for short-term memory, while a study carried out in the Nordic region linked excessive use of mobile phones with headaches and fatigue -- symptoms which generally disappeared as soon as cell phone use was discontinued.

But so far the lack of hard data has meant scientists have felt themselves unable to pronounce favorably or negatively on the effects of heavy mobile phone use -- apart from meting out (unintentionally) amusing advice such as the recommendation which appeared in a UK newspaper last year: "If you use a mobile phone a lot, you need your head examined."

In an effort to garner some concrete evidence about the possible effects of widespread long-term mobile phone use, the Geneva-based World Health Organization (WHO) has initiated the International EMF Project, designed to provide a reasonable risk assessment of the dangers of frequent exposure to radio frequency fields.

In what is the largest long-term study ever undertaken, EMF researchers will spend the next few years working with the International Agency for Research on Cancer, a WHO specialized agency in Lyon, examining 3,000 head and neck tumor patients. The typical mobile phone use of this group will then be contrasted with the cell phone habits of 3,000 tumor-free control patients, to determine whether any correlation exists. The results of the study, along with other investigations into other possible non-cancerous side effects of mobile phone use, are due to be evaluated in 2003 and 2004.

For the moment, many operators and manufacturers are playing it safe and recommending that users take precautionary action, such as alternating ears every few minutes during a long call, or taking advantage of new, low-radiation antennas and phone chips. Separate earphones and microphones are also increasingly widely used, as a way of keeping the possible radiation effects further away from the brain, as well as allowing hands-free operation of the phone.