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MARIN COUNTY'S NEWS MONTHLY - FREE PRESS
(415)868-1600 - (415)868-0502(fax) - P.O. Box 31, Bolinas, CA, 94924

May, 2006

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EMF Emissions and MERA
By Karen Nakamura

This paper has been looking at MERA, the Marin Emergency Radio Authority. This month we'll look at physical statistics.
Most Marinites want the first responder radio dispatch system to be there when disaster hits, but they also worry about microwave and electromagnetic waves that even the federal government admits may cause cancer and other health problems. The official version has it that emissions from the MERA antennas are too low to cause any damage past the thirty feet surrounding most sites.
What's the truth of the matter? Are our babies being bombarded with harmful electromagnetic/microwave emissions on a continuous basis or are those emissions so low that even in multiple forms, they are not enough to cause illness?

To find out, we'll examine three main sources of information; the United States Department of Labor's 1991 OSHA radiation and electromagnetic field employees memo found on its website and the 1999 "Q&A; about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields" issued by the FCC's Office of Engineering and Technology. We've also returned to Martin J. Nichols, MERA's director.

According to the OSHA memo, "The universe is full of EM [electromagnetic] fields and they are constantly mixing with the EM fields that are operating our electronic circuits."

Or as opponents have stated, "We are all antennas." Add the current proliferation of radiofrequency-microwave emissions and there's a real possibility of hazard.

The danger, it turns out, comes from Near-Field emissions within thirty feet of the antenna. The OSHA memo says, "Those working at sites are warned to take precautions with their equipment and themselves╔ it is especially important that workers be aware of the potentially hazardous╔ reactive near-field [within one wavelength]. The closer to the radiating source you get, the more caution should be exercised." The OSHA worker's memo continues. "╔Components of electromagnetic waves are absorbed by living tissue╔"

To reduce these dangers, the FCC has adopted recognized safety guidelines for radio frequency (RF) exposure. The Environmental Protection Agency (EPA), the Food and Drug Administration (FDA), the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) are also actively monitoring RF exposure. The safety guidelines include two tiers of recommended limits, one for the general population, normally fenced out of the near-field, and another for occupational exposure that occurs within feet of the antenna.

We contacted Martin J. Nichols, MERA director and asked him about the radiated power and dangerous fields around antennas. Using the Bolinas site as an example, his answer was:

"The site has to meet the FCC's established safety standards for public exposure. We believe the emissions will fall well below those guidelines." He continued in a more scientific mode. "The effective radiated power (ERP) at the proposed [Bolinas ranch] site will include 5 channels at 200 watts per channel. The maximum emissions level will be within about 30 feet of the antennas (within the fenced area of the site) and attenuates at the inverse square of the distance.

"For example, if the maximum power is at 30 feet (200 watts ERP), at 32 feet out it is 25 watts, [think 60 watt light bulbs], at 34 feet it is 6.25 watts, 36 feet 1.5 watts, and so on. The transmitter operates at 485 mHz which is below the FCC limits. The power line running into the site is 240 watts and also falls well below the limits."

The FCC's policies concerning environmental RF fields are designed to ensure that FCC-regulated transmitters do not expose the public or workers to levels of RF radiation considered by expert organizations to be potentially harmful. In 1997, the FCC adopted a provision that all transmitters regulated by the FCC were expected to be in compliance with the new guidelines on RF exposure by 2000.

Radio and television broadcast stations transmit their signals via RF electromagnetic waves. Broadcast stations transmit at various RF frequencies, depending on the channel, ranging from about 550 kHz for AM radio up to about 800 MHz for some UHF television stations. Operating powers ("effective radiated power") can be as little as a few hundred watts for some radio stations or up to millions of watts for certain television stations.

As far as the point-to-point, directional Microwave antennas are concerned; they transmit and receive signals across relatively short distances (from a few tenths of a mile to 30 miles or more). These antennas are normally mounted on a tower that provides a clear and unobstructed line-of-sight path between both ends of a transmission path. The RF signals from these antennas travel in a directed beam from a transmitting antenna to a receiving antenna. Microwave energy outside of the relatively narrow beam is minimal or insignificant.

In addition, these antennas transmit using very low power levels, usually on the order of a few watts. "Significant exposures from these antennas could only occur in the unlikely event that an individual stands directly in front of and very close to an antenna for a period of time."

MERA uses what is called "Land-mobile" communications that require the use of portable and mobile RF transmitting sources. These systems operate in narrow frequency bands between about 30 and 1000 MHz. There are three types of RF transmitters associated with land-mobile systems: base-station transmitters, vehicle-mounted transmitters, and hand-held transmitters.

Although base-station antennas usually operate with higher power levels, again, they are normally inaccessible to the public. Also, many of these antennas transmit only intermittently. The FCC continues, "For these reasons, such base-station antennas have generally not raised concerns with regard to possible hazardous exposure of the public to RF radiation."


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