There have been a number of health warnings over the years about possible radiation risks associated with the use of mobile phones. In case anyone is not taking these warnings seriously, British health researcher Dr. Vini Khurana puts it in language designed to get your attention:
"Mobile phones could have health consequences far greater than asbestos and smoking," he said.
Khurana a neurosurgeon who has published more than 30 scientific papers reviewed more than 100 studies on the effects of mobile phones. He has written a paper based on the research, which is currently being peer-reviewed for publication in a scientific journal.
Is he exaggerating? Khurana says the numbers bear him out. He points out that three billion people around the world now use a cell phone. That's three times the number of people who smoke, and smoking amounts for some five million worldwide deaths each year.
But are cell phones really a serious risk? Khurana expresses little doubt, saying "there is a significant and increasing body of evidence for a link between mobile phone usage and certain brain tumors."
The risks, he says, will become even more apparent in the years ahead.
Khurana believes governments should act immediately, but stops short of saying exactly what they should do. Separating people from their cell phones, at this point, might be beyond the reach of any earthly power.
Meanwhile, the cell phone industry remains unconvinced. Britain's Mobile Operators Association dismissed his study as "a selective discussion of scientific literature by one individual."
In the U.S., exploration of a possible link between mobile phones and health is moving at a slower pace. In January the National Academy of Sciences reported on its review of scientific evidence, requested by the Food and Drug Administration, by identifying areas where more research is needed.
Among the research requested by the Academy are human population studies of children and pregnant women, including childhood cancers and brain cancer; and a study of adults in the general population, comparing them with a group with medium to high exposure to mobile phones.
Last month, a study in the American Journal of Epidemiology, suggests that cell phone use contributes to at least some cancers.
The study found focused on cancer of the salivary gland, looking at 500 Israeli citizens who had developed the disease and 1,300 healthy subjects.
Researchers concluded that those who had held a mobile handset against one side of their head for several hours a day were 50 percent more likely to have a tumor in the salivary gland.
Since cell phones were introduced in the 1980s, there has been speculation of a heightened risk of cancer, caused by holding an electronic device against the head. There have been a number of studies, but no conclusive evidence one way or the other.
This latest study is different because it has focused on long-term users. Also, researchers say, previous studies have looked for tumor formation exclusively in the brain, not other parts of the body.
Cancer of the salivary gland, they point out, is very rare, and its location so close to where a handset is held makes the tumor-cell phone connection all the more intriguing.
The mobile communications industry has repeatedly questioned studies suggesting a cancer link. It argues cell phones have been shown to be safe, and should be considered so until they are conclusively shown to be unsafe.
Skeptics worry that radio-frequency radiation emitted from the devices might be harmful to human tissue, and might contribute to the formation of tumors. Dr. Siegal Sadetzki, who headed up the research team, notes that cancer risks appeared to be higher among rural cell phone users, because their mobile phones put off increased radiation to compensate for weaker signals.
But Sadetzki concedes her study is inconclusive and should be followed up with ongoing research. Even so, she says "precautions should be taken" in order to reduce risk, especially for children and young adults who use mobile phones.
Add to that worries about wireless computer networks. Last year, the British scientist who raised one of the early warnings about potential health hazards from cell phones has a new worry -- wireless Internet, or WiFi.
Sir William Stewart, chairman of Britain's Health Protection Agency, is lobbying British authorities for an investigation into WiFi's possible health risks, according to Britain's The Independent.
Stewart is concerned because wireless Internet may become more prevalent than mobile telephones.
A few individuals are known to suffer from a heightened sensitivity to electromagnetic radiation, but in recent years more and more physicians have expressed concern that repeated and prolonged exposure might be harmful to the wider population.
A study conducted in Finland found that people who have used cell phones for ten years or more are 40 per cent more likely to get a brain tumor on the same side of the head as they hold their handset. Research done in Sweden puts the risk at almost four times greater.
Stewart is reportedly concerned because of the similarity of the radiation emitted by cell phones and WiFi systems. But whereas cell phone radiation exposes only the person using the handset, WiFi radiation could affect everyone in the general vicinity.
Much of the concern is directed at children, who are seen as more vulnerable than adults to the effects of radiation, and because they will likely be exposed to increasing levels of radiation throughout their lives.
The Austrian Medical Association is pressing the government to ban the deployment of WiFi in schools.
Concerns about WiFi health effects have also been raised in the U.S.
In 2003, parents sued an Illinois school that installed a WiFi system, claiming the radiation was causing headaches and memory problems. Last year, Lakehead University in Thunder Bay, Ontario refused to install a campus WiFi system, citing possible health concerns.