Fact Sheet N� 193 AND PUBLIC HEALTH Mobile Telephones and Their Base Stations Mobile telephones, sometimes called cellular telephones or handys, are fast becoming an integral part of modern telecommunications. In some parts of the world, they are the most reliable or only telephones available. In others, cellular phones are very popular because they allow people to maintain continuous communication without hampering freedom of movement -- a quality widely appreciated both at work and leisure.
The rapid increase in use of mobile telephone handsets and construction of their base stations have also triggered concerns about the possible adverse health effects of cellular technology, including cancer, headaches and memory loss. With an estimated 190 million mobile telephones in use world-wide today, even small adverse effects on health could have major public health implications. In response to these concerns, WHO established in 1996 the International EMF Project to assess the existing scientific evidence of possible health effects of electromagnetic fields (EMF), including radiofrequency (RF) fields emitted by mobile phones and their base stations, and to recommend new research. When discussing possible adverse health effects of human exposure to RF fields it is important not to confuse RF fields with ionizing radiation, such as X-rays, gamma rays, or short-wave ultraviolet radiation. Unlike ionizing radiation, even high-intensity RF fields cannot cause ionization or radioactivity in the body. Because of this, RF fields are called non-ionizing radiation (NIR). Current mobile telephone systems operate at frequencies between 800 and 1800 MHz. Systems using 2100 MHz and higher frequencies may be introduced soon. These frequencies fall into the range between 1 MHz and 10 GHz (1 GHz =1 thousand MHz). Adverse health effects of RF exposure within this range have been researched over the past forty-five years. Health Effects of RF Fields between 1 MHz and 10 GHz: RF fields within this range are known to penetrate exposed tissues and produce heating due to energy absorption. The depth of penetration of the RF field into the tissue depends on the frequency of the field and is greater for lower frequencies. Even very low levels of RF energy produce a small amount of heat, but the body's normal thermoregulatory processes carry this heat away. However, international technical standards, according to which mobile telephones are made and their base stations are constructed, do not allow them to cause any significant heating (in other words there isn't a threshold below which there is no physiological effect of non ionising radiation radiated by base stations, but cooking of children in schools, homes. playgrounds, etc. is outlawed). Exposure to RF Fields of Low Intensity -- too low to produce significant heating (but not "too low" to have physiological effects such as :) -- has been reported to alter the electrical activity of the brain in cats and rabbits by changing calcium ion mobility. This effect has also been reported in isolated tissues and cells. Other studies have suggested that RF fields change the proliferation rate of cells, alter enzyme activity or affect the genes in the DNA of cells. These effects are not well established, nor are their implications for human health sufficiently well understood to provide a basis for restricting human exposure to RF fields of low intensity (not true ). Exposure to RF Fields and Cancer: Current scientific evidence indicates that exposure to low levels of RF fields, including those emitted by mobile phones and their base stations, is unlikely (not true - and in any case even if such outcomes were "unlikely" to be caused, triggered, enabled, aggravated by the effects of rf radiation, installation and operation in accordance with the Maastricht Precautionary Principle would still be prudent, to put it mildly) to induce or promote cancers.
It is important to emphasize that most RF studies conducted at frequencies exceeding 1 MHz, examined the results of acute exposure to high levels of RF fields - an exposure level that is not normally found in everyday life (unless you are in a school, home, playground etc, bathed in radiation from a powerful base station). However, with the advent of such devices as walkie-talkies and mobile telephones, it has become apparent that there were very few studies addressing the question of localized exposures to RF fields to the head and neck. RF fields from handsets: Even though mobile telephone handsets transmit much less power than a base station (and it is also worth pointing out that self irradiation resulting from personal handset use is a voluntary self inflicted injury ranking with alcohol or nicotine use - children in schools, homes and playgrounds are not offered a choice), the user's body absorbs significantly more power from the handset antenna (not true - if there is "less power" radiated, then how on earth can there be "more power" "absorbed" ?) -- a small rod emerging from the handset case. The head of the user receives the highest localized RF exposure. However, this localized RF exposure is limited by international guidelines and national standards and should not cause any local temperature increases in excess of 1�C (Gee ! - self inflicted cooking is not allowed) . For a person at 30 cm from a transmitting handset, RF absorption is 100 times less than that typically absorbed by the handset user. This exposure does not cause any measurable increase in body temperature. The amount of RF absorbed decreases rapidly at greater distances from the handset (another argument in favour of operation in accordance with the Maastricht Precautionary Principle by achieving appropriate separation through distance or insulation). WHO's International EMF Project has identified specific scientific studies needed to address the problem of localized exposure. One important study being undertaken by the International Agency for Research on Cancer -- a specialised cancer research organization of WHO -- is looking at the relationship between mobile telephone use and potential long-term adverse health effects. RF Fields Near Base Stations: Base station RF antennas are narrow and about 1 metre long. Several such antennas are mounted on a tower that is generally 15 to 50 m high or on buildings. These antennas each emit a confined, almost spotlight-like beam of RF that is roughly parallel to the ground. Because of the narrow vertical spread of the beam, the RF field intensity on the ground directly below the antenna is low ("15 to 50 m" below the radiating antennas) and decreases rapidly as one moves away from the antenna. At all distances, the RF field levels on the ground from base stations are well within international RF guidelines (which admittedly define hazard as cooking) for exposure of the general public. Some antennas mounted on rooftops have fences to keep people away from places where the RF fields exceed these limits. Since antennas mounted on the sides of buildings direct their power outward, people inside are not highly (Gee!) exposed. Measurements of RF intensities on the ground near base station antennas have ranged from 1/40 to 1/250 or less of international guidelines limiting public exposure (to the danger of getting cooked), depending on the distance from the antennas. TV station antennas operating at similar frequencies (500-800 MHz) broadcast greater total power than base stations and emit RF fields to the ground which are about � to about 1/500 of the international guideline limits. What should be done while research is ongoing? (easy peasy : adopt and rigorously enforce the Maastricht Precautionay Principle) : One of the objectives of the International EMF Project is to help national authorities weigh the benefits of mobile telecommunications technology against the detriment of any, even subtle, adverse health effects, and decide what additional protective measures may be needed. It will take about 5 years for the required research to be completed, evaluated and published by WHO. In the meantime, WHO recommends:
For further information, please contact Igor Rozov, Health Communications and Public Relations, WHO, Geneva, Switzerland (4122) 791 2532/2584, fax (4122) 791 4858, email: [email protected] All WHO Press Releases, Fact Sheets and Features can be obtained on Internet on the WHO home page http://www.who.ch |
read notes from a Royal Society of Canada report on human
biological effects of radio frequency radiation here
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