The sudden and massive increase in mobile phone usage has led to concerns that these devices can harm human health.
There are fears that people who use these phones a lot could be a greater risk of some rare forms of cancer, dementia, depression, sleeping disorders or other illnesses.
There are also concerns about the siting of the mobile phone network’s base stations and masts as they emit electromagnetic radiation.
Scientific studies has so far proved inconclusive, however, and the World Health Organization has concluded that they provide no evidence for health impacts.
In 2007, the European Commission Scientific Committee on Emerging and Newly Identified Health Risks concluded that normal exposure to mobile phone radiation cannot cause headaches, dizziness, brain cancers and effects on the nervous and reproductive systems, but it said more studies on the risks to children were needed.
Other governmental and nongovernmental bodies agree on the need for more research.
Interphone, a ten-year study in 13 countries was set up in 2000 to assess links between mobile phone use and various illnesses. In May 2010 it published its report on phones and brain tumours.
However, the researchers concluded that “biases and errors” within their study meant they were unable to make any clear link between mobile phone use and brain tumours.
Also in 2010, five European nations launched another long-term study called Cosmos that will track 250,000 mobile phone users over more than 20 years to find out about how people use phones and whether this is linked to health problems. The first results are expected within ten years.
Concerns about mobile phones are divided into those about the phones themselves and those about the masts or base stations.
As people hold phones to their heads, this means that the head absorbs some of the radiation emitted by the phone.
One effect of this is that tissues at the surface of the head can heat up, but only slightly and about ten times less than happens because of sunlight. Any heat created will be rapidly dispersed by the movement of blood in our heads.
Many people have reported health concerns immediately after using mobile phones (such as headaches, dizziness and loss of attention), a condition termed electromagnetic hypersensitivity.
But current research suggests that these symptoms are just as likely in people who have not been exposed to mobile phone radiation.
Some researchers say however that it is too early to assess whether mobile phones can cause health problems over the long term – such as by inducing brain tumours, as these can take years to develop.
There are also concerns about the health of people living and working near the masts (antennae) at mobile phone base stations as they emit continuous radiation.
Such people have often reported health problems but it is very difficult to scientifically assess whether these are caused by the radiation or whether people simply associate common symptoms with the masts they are aware of in their local environments.
In the absence of strong evidence to link mobile phones and disease, many health authorities limit their advice to simple precautionary steps.
These include recommending the use of hands-free headsets, which keep the source of radiation away from the head, and discouraging children from using mobile phones for non-essential calls.
In many countries base station emissions must comply with safety guidelines and some countries have ruled that masts cannot be erected close to schools or homes.
The International Commission for Non-Ionizing Radiation Protection’s standards have been adopted by more than 80 countries.
Top sources for journalists covering this topic include the World Health Organization, which is set to issue recommendations about mobile phones in 2011.
Because cancers grow slowly, any increase due to mobile phone use is unlikely to have become apparent yet.
Part of the problem with reporting on mobile phone radiation is the word radiation. It brings to mind other hazardous forms of radiation, such as nuclear.
Journalists must remember that light is also a form of radiation, and that the term is just a piece of scientific jargon that describes any form of energy that is transmitted in rays. Some forms of radiation are harmful and some are harmless.
It is important for journalists who are reporting on claims about the safety or non-safety of mobile phones to check their sources of information very carefully to see whether they have links either to mobile phone companies or to companies that are marketing products that would benefit from negative publicity about phones.
Scientific studies in peer-reviewed academic journalists are the best source of information but even with these it is important to find out how studies have been funded.
The British medical doctor Ben Goldacre has made it a personal mission to expose bad science, particularly as it is reported in the mainstream media. His blog is a good source of analysis of stories about mobile phone radiation, among other issues.
The Environmental Working Group, a US-based advocacy group, has posted an online tool that let people compare the levels of radiation emitted by 1,200 models of mobile phones.