Electromagnetic fields are generated by presence of electric charges and current flow, and in households are generally associated with extremely low frequencies (ELF) generated by electrical appliances, wires and power lines.

Some debate still exists over the actual health hazards associated with residential exposure to ELF, however, the prevailing opinion of the scientific community and that of the National Institutes of Health (1998 press release statement regarding power-frequency fields) is that EMF associated with residential exposure can only be classified as a “possible,” but not “probable” human carcinogen. Meaning, it cannot be excluded as a cause, but has not been shown to be a cancer-causing agent. One way to measure the levels of EMF in the home is with a Gauss meter. However, since no action level has been established by the EPA, it is difficult to determine the level of concern based on these findings. Non-residential sources of stronger electromagnetic fields that should be seen with caution are high tension transmission power lineselectric transformers and electrical substations. 

Cellular phone base antennas, radar stations, TV and radio antennas, and microwave devices are sources of electromagnetic radiation (ER). There has been a lot of controversy about the effect of electromagnetic radiation on the health of persons and animals living close to those devices. Besides the elevation of temperature of organic tissue (heating effect) for short distance exposure, there are other possible risks (non-heating effects) cited in the technical literature such as: cancer, including brain cancer and leukemia; insomnia; headache; brain and nervous system damage; genetic damage to embryos and cells; cornea and retina damage, etc. No government regulations or standards have been established in the U.S. at the moment of writing this report. However, in Europe and Australia some townships and cities have established precautionary regulations that in most cases require the installation of sources of electromagnetic radiation and particularly antennas at considerable distance (typically in the range of 100-500 meters or about 300-1500 feet) from schools, homes, hospitals and public or office buildings. The WHO (World Health Organization) of the UN is conducting since 1996 an International EMF Project to assess health and environmental effects in human health of exposure to static and time varying electric and magnetic fields in the frequency range 0-300 GHz. Some publications have been presented by the WHO regarding these topics (See Fact Sheet N° 193) on the use of cell phones; and Fact Sheet N° 304 for base antennas and wireless networks). These publications indicated that considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak radio frequency signals from base stations and wireless networks cause adverse health effects. Similar conclusions were presented regarding the use of mobile phones.
A recent release (Press release 208, 2011) by the WHO indicated that radiation from cell phones might cause cancer. The agency now lists mobile phone use in the same "carcinogenic hazard" as some chemicals, finding enough evidence to categorize personal exposure as "possibly carcinogenic to humans." Evidence of increase in glioma and acoustic neuroma brain cancer for mobile phone users was found, but have not been able to draw conclusions for other types of cancers. Additionally, there could be a whole host of other effects like cognitive memory function, since the memory temporal lobes are where we hold our cell phones."
In any case, the precautionary principle regarding electromagnetic fields and electromagnetic radiation must be applied and prudent avoidance should be considered until more conclusive evidence is available. The physiological effects of radio frequencies and electromagnetic radiation of base stations and other sources diminishes with the distance to the source.

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