Hang up - updates - train passengers exposed to cell phone electromagnetic radiation - Brief Article

Passengers on packed trains and subways may be exposing themselves to electromagnetic fields far more intense than those recommended under international guidelines. The problem? Crowds of commuters using cellular phones at the same time.

When hundreds of mobile phones emit radiation, their total power is found to be comparable to that of a microwave oven or even a satellite broadcasting station, according to a recent study published in the February 2002 issue of the Journal of the Physical Society of Japan.

Physicist Tsuyoshi Hondou, formerly of Tohoku University in Sendai, Japan, and now working at the Curie Institute in Paris, says Japanese commuter trains are often packed with people surfing the Web on their cellular phones. The trend spurred him to find out what effect this had on the electromagnetic radiation inside a train.

Starting with blueprints obtained from a carriage manufacturer, Hondou worked out the ratio of window area to structural metal for a typical carriage.

He then used this number to work out what proportion of microwave radiation from cell phones would be transmitted out of a carriage through the windows and how much would be reflected back inside.

The calculations show how microwaves from different phones can add together--much like light from different lamps can increase the overall illumination in a room.

By taking both reflection and the cumulative effect of the radio waves into consideration, Hondou found that the resulting electromagnetic field in a train car exceeds the maximum exposure level recommended by the International Committee for Non-Ionising Radiation. "High levels of radiation are possible even if the train isn't very crowded," Hondou says. His findings point to what could become an important environmental issue, especially as new wireless devices and laptop computers come onto the market. He suggests that train operators take notice.

"At the moment, we have no regulation on the use of mobile phones in areas where many people are together," he says, adding that the problem could also arise in other crowded, confined places such as buses and elevators.

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