SPECIAL Report
The use of Cellular Telephones:Is it a Health Hazard?
Theincreased use of cellular telephones in the Cayman Islands hasraised questions whether this modern form of communication posesa health hazard for its users. Following inquiries made, and inthe interest of continuing with its commitment to communicatewith the public, the Cayman Islands Health Services recently submittedinformation in connection with this issue, which was producedby the World Health Organization (PAHO).
In recent weeks the issue of cellular telephoneuse has been raised in terms of being a health hazard and it hasbeen recommended that people who use cellular phones regularlypurchase a hands free head phone device which attaches to thecellular phone to and allows the user the freedom of talking intothe headset without having to physically hold up the phone tothe ear.
However, with the discussion continuing on the entire aspect ofexposure to radio frequency and surrounding Electro magnetic fieldswhich emit from base stations to the cellular phone and its user,hand held or hands free the verdict on the overall exposure isyet to be determined.
It is obvious that locally there has an increase in the numberof subscribers as evidently Cable and Wireless has now exhaustedits 916 cellular prefix numbers and has started issuing 926 numbersto new subscribers. The exact numbers have not been obtained bypress deadline.
Obviously sales have increased for Cable and Wireless who arenow in an active sales and marketing campaign for a new prepaidmobile phone service locally called, "Pay as you Go"featuring the talking (Nokia brand in appearance) cellular telephonecartoon complete with intellectual looking glasses or designershades depending on your interpretation.
In terms of safe driving practices, the traffic department isalso recommending that cellular telephone users purchase the device.The Cayman Islands Medical Officer of Health, Dr. Kumar also recentlyreleased a document fact sheet courtesy of the World Health Organisationwith information related to the use of cellular telephones, ina document titled "Electromagnetic Fields and Public Health- Mobile Telephones and their base stations." Revised inJune 2000 from the World Health Organisation. The document states:
Mobile telephones now an integral and popular part of modern telecommunicationsand often regarded as the most reliable in some parts of the worldas the only telephones available. Mobile phones are popular becausethey allow people to maintain continuous communication withouthampering freedom of movement.
This fact sheet has been updated in light of recent reviews ofthe effects on human beings of exposure to radiofrequency (RF)fields conducted by the WHO in November 1999, the Royal Societyof Canada (1999), and a review on mobile phones and health byan expert committee in the united Kingdom (EGMP 2000).
In many countries over half the population already use mobilephones and the market is still growing rapidly. The industry predictsthat there will be as many as 1.6 billion mobile phone subscribersworldwide in the year 2005. Because of this, increasing numbersof mobile base stations have had to be installed.
Base stations are low powered radio antennae that communicatewith users' handsets. In early 2000 there were about 20,000 basestations in operation in the United Kingdom and about 82,000 cellsites in the United States with each cell site holding one ormore base stations.
Given the immense number of users of mobile phones even smalladverse effects on health could have major public health implications.Several important considerations must be kept in mind when evaluatingpossible health effects of RF fields. One is the frequency ofoperation as current mobile phone systems operate at frequenciesbetween 800 and 1800 MHz.
It is important not to confuse such RF fields with ionising radiationsuch as x-rays or gamma rays. Unlike ionising radiation. RF fieldscannot cause ionisation or radioactivity in the body and becauseof this RF, fields are called non-ionising.
Mobile phone handsets and base stations present quite differentexposure situations RF exposure to a user of a mobile phone isfar higher that to a person living near a cellular base station.However, apart from infrequent signals used to maintain linkswith nearby base stationsm the hand set transmits RF energy onlywhile a call is being made, whereas base stations are continuallytransmitting signals.
Mobile phone handsets are low powered RF transmitters, emittingmaximum powers in the range of 0.2 to 0.6 watts. Other types ofhand held transmitters, such as 'Walkie talkies' may emit 10 wattsor more. The RF field strength (and hence RF exposure to a user)falls off rapidly with distance from the handset.
Therefore the RF exposure to a user of a mobile phone located10s of centimetres from the head (using a 'hands free' appliance)is far lower that to a user who places the headset against thehead. RF exposures to nearby people are very low.
Base stations transmit power levels from a few watts to 100 wattsor more depending on the size of the region or 'cell' that theyare designed to service. Base station antennae are typically about20-30 cm in width and a metre in length mounted on buildings ortowers at a height of from 15 to 50 metres above ground.
These antennae emit RF beams that are typically very narrow inthe vertical direction but quite broad in the horizontal direction.Because of the narrow vertical spread of the beam, the RF fieldintensifies at the ground directly below the antenna. The RF fieldintensity increase slightly as one moves away from the base stationand then decreases at greater distances from the antenna.
Typically within 2-5 metres of some antennae mounted on rooftops,fences keep people away from places where the RF fields exceedexposure limits. Since antennae direct their power outward anddo not radiate significant amounts of energy from their back surfacesor towards the top or bottom of the antenna, the levels of RFenergy inside or to the sides of the building are normally verylow.
Other RF sources in the community are paging and other communicationsantennae such as those used by fire, police and emergency servicesthat operate at similar power levels as cellular base stations,and often at a similar frequency. In many urban areas televisionand radio broadcast antennae commonly transmit higher RF levelsthan do mobile base stations.
RF fields penetrate exposed tissues to depths that depend on thefrequency - up to a centimetre at the frequencies used by mobilephones. RF energy is absorbed in the body and produces heat, butthe body's normal thermoregulatory process carries the heat away.
All established health effects of RF exposure are clearly relatedto heating. While RF energy can interact with body tissues atlevels too low to cause any significant heating, no study hasshown adverse health effects at exposure levels below internationalguideline limits.
Most studies have examined the results of short-term, whole bodyexposure to RF fields at levels far higher than those normallyassociated with wireless communications. With the advent of suchdevices as walkie-talkies and mobile phones, it has become apparentthat few studies address the consequences of localised exposureto RF fields to the head.
Who has identified research needs to make better health risk assessmentand promoted the research in funding agencies. Briefly, at presenttime this research indicates:
Cancer:
Current scientific evidence indicatesthat exposure to RF fields, such as those emitted by mobile phonesand their base stations, is unlikely to induce or promote cancers.Several studies of animals exposed to RF fields similar to thoseemitted by mobile phones found no evidence that RF causes or promotesbrain cancer.
While one 1997 study found that RF fields increased the rate atwhich genetically engineered mice developed lymphoma, the healthimplications of this result are unclear. Several studies are underwayto confirm this finding and determine any relevance of these resultsto cancer in human beings. Three recent epidemiological studiesfound no convincing evidence of increase in risk of cancer orany other disease with use of mobile phones.
Other Health Risk:
Scientist have reported other effectsof using mobile phones including changes in brain activity, reactiontimes, and sleep patterns. These effects are small and have noapparent health significance. More studies are in progress totry to confirm these findings.
Driving:
Research has clearly shown an increasedrisk of traffic accidents when mobile telephones (either handheldor with a 'hands-free' kit) are used while driving.
Electromagnetic Interference:
When mobile phones are used close tosome medical devices (including pacemakers implantable defibrillators,and certain hearing aids) there is the possibility of causinginterference. There is also the potential of interference betweenmobile phones and aircraft electronics.
Who is conducting RF research which is being co-ordinated in over10 countries by ARC (the international Agency for Research onCancer) - a specialised cancer research agency of WHO - to identifyif there are links between use of mobile phones and head and neckcancers.
The study is anticipated to be completed in 2003.