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III base station,cannot cause such effects. stations,indicates that base stations expose As mentioned previously,a typical base The most common effect of fields from the public to levels of RF energy many station consists of a small shed or enclosure base stations is a slight warming of tissue hundreds or thousands of times less than for radio equipment and a set of antennas near an energized transmitting antenna. the modem limits set by standards-setting mounted 100 or more feet above ground. This is called the thermal effect.Some organizations, including ANSI,ANSI/ In many cases,base stations can be people have wondered whether athermal IEEE,the National Council on Radiation designed to be unobtrusive. If there is effects from weak radio fields pose any Protection (NCRP),and International already an antenna tower,water tower,or health consequences.Most scientists say Radiation Protection Agency(IRPA). office building in the area where a system no,and claims to the contrary have not One expert at the Symposium described licensee needs to install a new base station, been reproduced in laboratory experiments. exposures from base stations as almost a the licensee can use that existing structure "nonissue"in terms of applicable safety and avoid putting up its own antenna Various srandartis-setting bodies have adopted standards. tower.Where new tower cons limits or guidelines for the exposure of people construction is necessary camouflage can, in some cases, to radio frequency(RF)energy. In 1985, IV. There Is No Evidence Base mitigate the visual impact of the structure. the FCC adopted the"C95.1-1982"expo Stations Pose Interference sure standard issued by the American Symposium participants presented National Standards Institute.(ANSI is the Problems anecdotal evidence and summaries of ration's preeminent private standard- Radio signals—if they are strong enough studies to the effect that base stations do coordinating body.)That standard set a —can sometimes interfere with electronic not appear to depress the values of single exposure limit for both works and devices such as radio and television surrounding parcels and homes.Participants the general public.Permissible exposure receivers,stereo systems,medical monitors, also described the public-interest benefits under the 1982 ANSI standard from a cel- and automotive systems in unintended of locating base stations on public property. lular base station is about 2700 micro- ways.Consumer electronic devices vary There appear to be no benefits to iebuicting warts per square centi-meter,averaged in their ability to coexist with radio signals. base stations from areas with potentially ,er six minutes. (One microwatt is one Some manufacturers build high levels of sensitive populations such as school children. e-millionth of a wu„and one square immunity to interference into their prod- Finally,Symposium participants and pan- centimeter is an area about the size of an uccs.Other manufacturers include none, elists described the strong federal interest adult's pupil in dim light.) or virtually none.The signals from base in a well-developed telecommunications Based on an extremely low risk of exposure stations diminish rapidly with distance.As infrastructure.The FCC requires a cellular in excess of the 1982 ANSI standard,the a result,in areas where people live and system operator to detail,when filing for FCC excused cellular base stations from work,the signals are too weak to upset renewal of its system license,how it has having to demonstrate compliance with electronic devices.There is no evidence expanded system capacity to meet the the standard.In 1992,ANSI supplanted that the placement of a base station in or public's demand for service.If an operator its 1982 standard with a 1991 exposure near a community has resulted in elec- fails to install new base stations to satisfy standard drawn up by the Institute of tronic interference to consumer electronics. that demand,the operator may not gamer Electrical and Electronic Engineers(11-_r1-), There have been reports of interference a"renewal expectancy,"and may not a prestigious professional society.For to medical devices from the radio waves obtain a renewal of its license.The strong occupational exposures from cellular base emitted by portable cellular phone or federal policy preference for system stations, the 1992 limit is the same as the security guards'walkie-talkies;there have expansion can conflict with local govern- 1982 limit,and the six-minute averagingnot been any reports of such interference ment efforts to restrict new base stations. period remains the same.In areas frequented from cellular base stations. This conflict could be a source of signifi- by the general public,the 1992 standard's IV. Base Stations and Land Use cant federal-local tension in the future. limit is five times lower than the 1982 standard,although the averaging time Issues increased CO 30 minutes. The construction of a base station usually The FCC is updating its exposure limits. requires one or more municipal permits. The FCC has proposed to adopt the 1992 Depending on state and local zoning laws, ANSI standard as the most recent and corn- the required permit ranges from a simple Oensive of all the published standards. building permit issued upon application to FCC is also reevaluating its exclusion a special exception or zoning variance of base stations from having to demonstrate requiring a public hearing.Where the law compliance with RF exposure limits, considers a base station to be part of the public utility infrastructure,obtaining the A large body of data,based on actual necessary authorization to build such a 3 measurements of exposures from base facility is usually not complicated.