LONDON -- Train passengers who hate it when other commuters use mobile phones on board may have every right to get angry, according to BBC News.

Research carried out by scientists in Japan suggests that using a mobile phone inside a train carriage could have serious health risks for other passengers.

They found that electromagnetic radiation levels inside trains can exceed international safety limits if even a small number of passengers are using their phones.

This is because the microwave radiation emitted from handsets has effectively no where to go and simply bounces back off the carriage's metal structure.

Tsuyoshi Hondou, from Tohuku University, used the plans of a typical train carriage to calculate the impact of mobile phone mivrowave radiation.

Unsafe levels

He found that very little radiation managed to escape through windows and was instead reflected inside.

He discovered that if just 30 people in a standard carriage with 151 passengers used their phone radiation levels exceeded the limits recommended by the International Committee for Non-Ionising Radiation.

But he added that because the radiation can build up, levels can be high in carriages with fewer passengers.

"It's possible even if the train is not crowded," he told New Scientist magazine.

Mr Hondou said the findings, originally published in the Journal of the Physican Society of Japan, were worrying in light of the growth in the number of people with WAP phones and other wireless electronic devices.

He suggested train operators should consider introducing rules on the use of mobile phones in carriages.

But he added that the effects seen in train carriages may also apply to buses and elevators.

"At the moment we have no regulation on the use of mobile phones in areas where many people are together.

Further research

Prof Les Barclay, who is a member of the Department of Heatlth mobile phone research committee, suggested that the health risks were minimal.

"Signals from the antenna and mobile phone decrease very rapidly as you move away from the phone," he said.

"By the time a signal has been reflected by a distant wall it will be at a very low level."

Prof Barclay said the committee was not planning to study the use of mobile phones on trains.

But speaking to BBC News Online, he added: "It is something we could look into. It would be rather an easy job to do that kind of assessment."

A spokeswoman for the Rail Passengers Council said it would be interested in finding out more about the issue.

"In terms of the health impact of using mobile phones on trains, this is not something we have researched in the past.

"But it is certainly something we would be interested in. While we probably wouldn't carry out such a study ourselves we would be interested in any findings."