Passengers on packed trains could be exposed to electromagnetic fields far higher than those recommended under international guidelines when large numbers of commuters all using their mobile phones at the same time. This can happen in buses, subway cars and elevators, and in other closed environments, such as offices, as well.

Tsuyoshi Hondou, a physicist from Tohoku University in Sendai, Japan, says Japanese commuter trains are often packed with people surfing the web on their cellphones. He decided to find out what effect this has on the electromagnetic radiation in a train car.

Starting with plans of a typical train car that he got from a Japanese train operator, Hondou worked out the ratio of window area to structural metal. He then used this to work out what proportion of the microwave radiation from the cellphones would be transmitted out of a carriage through the windows and how much would be reflected back inside.

Hondou then calculated how microwaves from mobile phones distributed throughout a train or subway car would add together, the same way light from different lamps would increase the overall illumination in a room. He found that when both reflection and the cumulative effect of the radio waves were taken into consideration, the resulting electromagnetic field in a train carriage could exceed the maximum exposure level recommended by the International Committee for Non-Ionizing Radiation (ICNIRP). “It’s possible even if the train is not crowded,” Hondou says.

For a standard railway car, with a capacity of 151 people, Hondou’s calculations show that it is possible to exceed ICNIRP exposure limits if 30 people, each with a mobile phone that emits radio waves at a power of 0.4 watts, all use their phones at the same time. The peak power a mobile phone is allowed to produce is two watts.

Les Barclay, a radio engineering consultant, is cautious about Hondou’s findings. While he concedes microwaves will bounce around inside carriages and boost field levels, the increase should be minimal, he says, because power drops off a short distance away from each phone. But Hondou says that the drop-off doesn?t happen if the radio waves are bounced off the train’s walls.

Hondou says his findings point up what could become a new environmental issue, especially as new wireless devices and laptop “connections” come onto the market, and says, “At the moment, we have no regulation on the use of mobile phones in areas where many people are together.”

If everyone on the train used a Waveguard, radiation would be no problem. To learn about waveguard,click here.

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