There are hundreds of them around the State and more are planned. Scientists consider them very safe, and their signals are thousands of times weaker than radio and television signals.

So why is it that the transmitters for mobile telephones, known as base stations, have provoked so much opposition on health grounds?

According to Dr John Moulder, professor of radiation oncology at the Medical College of Wisconsin, international scientific consensus is that there is no health hazard associated with living, working, playing, or going to school near a base station.

And although Irish mobile phone operator, Esat Digifone, says mobile phone users are exposed to around 10,000 times more radiation from the phones than we all are from the base stations, Dr Moulder says he gets 50 questions about the base stations for every question about the mobiles, on his Website on cellular phone antennas and human health.*

In his opinion, the main reason for this is that living or working near base stations is involuntary, while using a phone is voluntary. However, he says, FM radio and UHF television antennas are 100 to 5,000 times more powerful than base stations, and radiation at their frequencies is absorbed more in human bodies than radiation at mobile frequencies. However, they are usually on higher masts.

Mr Declan Drummond, acquisitions manager at ESAT Digifone, which has erected more than 200 base stations around the State makes the same point. He says while radio and television transmitters may transmit hundreds of thousands of watts, the average base station only transmits about 10 watts, which because it is concentrated in certain directions, is equivalent to 200 watts in the main beam. This directionality means the amount of radiation at the bottom of the base station masts is less than at 100 metres away. Mr Drummond says Digifone's measurements at various distances from antennas show field strengths tens of thousands of times lower than guidelines.

The State has very little equipment for measuring radiation fields around base station masts. Up until now the only meter, owned by Forbairt, can measure at frequencies up to 1,000 MHz, just enough for GSM signals but not enough to measure the new DCS 1800 or MMDS signals. For these higher frequencies, new equipment is being procured, but the GSM field strengths measured have so far been so low they would register as zero on standard safety equipment, according to Department of Public Enterprise sources.

Besides dedicated masts, Mr Drummond says Digifone has used church towers, grain silos, one lighthouse, and water towers to house base stations, but thinks many of the objections are because people find purpose-built masts unattractive. In some areas, he says, he thinks people are worried new GSM masts will be "Trojan horses" for MMDS transmitters. He says people who want the continuation of the free television deflector schemes don't want any new masts which may subsequently be used for MMDS transmitters.

In future we are likely to see a proliferation of many, small base stations, particularly in metropolitan areas. Already micro-cells are being installed in offices, where a tiny base station gives mobile coverage within a building. These use minute signal strengths, microwatts according to one scientist. Eoin Licken can be reached at eoin@stilet.to

*(www.mcw.edu/gcrc/cop/cellphone-health-FAQ/toc.html).