Electromagnetic Field Safety

While power lines aren't pretty, they are generally safe to live around.

Many sites on the Internet promulgate the view that electromagnetic fields, sometimes referred to as EMFs, are dangerous. With our homes now filled with electronic equipment, and the air teeming with electromagnetic radiation from cell phones, radios and computers, you might be persuaded to think you're being affected by unseen hazards. The question remains, however, as to whether it presents a real danger.

ELF

Much of the controversy surrounding EMF centers on the invisible radiation surrounding power lines. The alternating current flowing through utility lines in the United States runs at a 60 hertz frequency. This produces what's called ELF, for extremely low frequency radiation. Though millions receive exposure to it every day, evidence connecting it to health problems is uncertain.

Magnetic Fields

ELF, as with all electromagnetic radiation, takes the form of both electric and magnetic fields. Each field type has its own strength measurement. The unit of magnetic field strength is the tesla, where the Earth's magnetic field measures 0.05 millitesla (thousandths of a tesla, or mT). The American Conference of Governmental Industrial Hygienists has set an exposure limit of 1 mT for magnetic fields from 60 hertz electricity.

Electric Fields

ELF's electric field component is measured in volts per meter. The ACGIH has set a limit of 25,000 volts per meter as the strongest electric field to which you should be exposed at these low frequencies. While magnetic fields penetrate most materials, you can easily block electric fields with the proper use of electrical grounds and shielded cables.

Studies

According to the World Health Organization, studies conducted on people exposed to a 5 mT magnetic field experienced no discernible reaction. They saw no effects for body temperature, heart rate or blood pressure that would indicate stress. For electric fields, the WHO studies of exposures up to 20,000 volts per meter had no significant effects. Studies of animal reproduction and development with electric field exposures up to 100,000 volts per meter showed no abnormalities.

Workplace

Health and safety organizations set higher limits for ELF exposure in the workplace, as industrial and commercial equipment have more electrical power than home appliances. The International Commission on Non-Ionizing Radiation Protection has set workplace limits on ELF electric fields at 8,300 volts per meter and 0.417 mT for magnetic fields.

Home

Because you'll find children at home and not in industrial settings, safety organizations set limits for home exposure more conservatively. The ICNIRP recommends residential limits for ELF electric fields at 4,200 volts per meter and 0.083 mT for magnetic fields.

References

• World Health Organization: Electromagnetic Fields and Public Health
• American Industrial Hygiene Association: ELF Fields
• Cool Magnet Man: How Strong are Magnets?