Another area of concern is the radiation emitted by the fixed infrastructure used in mobile telephony, such asbase stationsand their antennas, which provide the link to and from mobile phones. This is because, in contrast to mobile handsets, it is emitted continuously and is more powerful at close quarters. On the other hand, field intensities drop rapidly with distance away from the base of the antenna because of theattenuation of power with the square of distance. Base station emissions must comply with safety guidelines (seeSafety standards and licensingbelow). Some countries however (such asSouth Africafor example) have no health regulations governing the placement of base stations.
Several surveys have found increases of symptoms depending upon proximity to electromagnetic sources such as mobile phone base stations.
A 2002 survey study by Santiniet al.inFrancefound a variety of self-reported symptoms for people who reported that they were living within 300Â metres (984 ft) ofGSMcell towers in rural areas, or within 100Â m (328 ft) of base stations in urban areas. Fatigue, headache, sleep disruption and loss of memory were among the symptoms reported.[58]Similar results have been obtained withGSMcell towers inSpain,Egypt,PolandandAustria.No major studies have been reported in which health effects did not occur on actual populations living near mobile base stations. However, there are significant challenges in conducting studies of populations near base stations, especially in assessment of individual exposure.Self-report studies can also be vulnerable to thenocebo effect.
A study conducted at theUniversity of Essexand another in Switzerlandconcluded that mobile phone masts were unlikely to be causing these short term effects in a group of volunteers who complained of such symptoms.The Essex study has been criticised as being skewed due to drop-outs of test subjects,although these criticisms were answered by the authors.
As technology progresses and data demands have increased on the mobile network, towns and cities have seen the number of towers increase sharply, including3Gtowers which work with larger bandwidths.Many measurements and experiments have shownthat transmitter power levels are relatively low - in modern2Gantennas, in the range of 20 to 100 W, with the 3G towers causing less radiation than the already present 2G network. An average radiation power output of 3 W is used. The use of 'micro-cell geometries' (large numbers of transmitters in an area but with each individual transmitter running very low power) inside cities has decreased the amount of radiated power even further. The radiation exposure from these antennas, while generally low level, is continuous,
Experts consulted by France consider it is mandatory that main antenna axis not to be directly in front of a living place at a distance shorter than 100 meters.This recommendation was modified in 2003to say that antennas located within a 100-metre radius of primary schools or childcare facilities should be better integrated into the cityscape and was not included in a 2005 expert report.
Occupational health hazards
Telecommunication workers who spend time at a short distance from the active equipment, for the purposes of testing, maintenance, installation, etcetera, may be at risk of much greater exposure than the general population. Many times base stations are not turned off during maintenance, but the power being sent through to the antennas is cut off, so that the workers do not have to work near live antennas.
A variety of studies over the past 50 years have been done on workers exposed to highRFradiation levels; studies includingradarlaboratory workers, military radar workers, electrical workers, and amateur radio operators. Most of these studies found no increase in cancer rates over the general population or a control group. Many positive results could have been attributed to other work environment conditions, and many negative results of reduced cancer rates also occurred.
Safety standards and licensing
In order to protect the population living around base stations and users of mobile handsets, governments and regulatory bodies adopt safety standards, which translate to limits on exposure levels below a certain value. There are many proposed national and international standards, but that of the International Commission for Non-Ionizing Radiation Protection (ICNIRP) is the most respected one, and has been adopted so far by more than 80 countries. For radio stations, ICNIRP proposes two safety levels: one for occupational exposure, another one for the general population. Currently there are efforts underway to harmonise the different standards in existence.
