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The popularity of cell phones and wireless communication devices has resulted in a proliferation of cell towers across the American landscape. Opposition to the placement of these towers has sometimes developed among segments of the population, usually based upon aesthetics, concern over the electromagnetic radiation, or both.
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EMF Services can conduct testing and site assessments for individuals, schools, building managers, condo boards, or municipalities who wish to become aware of the RF levels at a location near cell phone or broadcast towers. The report that we provide will permit comparison of measured levels with FCC Maximum Permissible Exposures (MPEs), precautionary guidelines, and routine background levels for comparable environments. If new antennas or towers are planned for your location, our site survey can be used to establish a baseline RF level for later comparison (before and after testing). Follow-up readings are provided at reduced cost compared to the initial survey.
The purpose of this testing is to empower you to make responsible, fact-based decisions about the RF environment surrounding your community, facility, home, or school. We use advanced equipment to perform the most accurate and comprehensive RF exposure assessments in the industry. All services are delivered by personnel with several years of experience in planning and directing the installation of radio communication facilities, using equipment with current factory calibration certificates. If exposure reduction measures are desired, recommendations will be included in the report. The greatest advantage of our surveys over that of other providers is the ability to address the issue of low-level, long-term, non-thermal exposures, and to articulate the scientific rationale for a precautionary exposure guideline.
EMF Services no longer performs standard RF compliance surveys. We provide only enhanced testing services that involve more detailed data collection, and a more extensive and broader coverage report, than a conventional compliance survey. Our surveys incorporate procedures and equipment to separately measure cellular power density, in addition to the composite power density (the combination of all RF signals present). We use top quality professional equipment, and extensive procedural safeguards, to ensure the highest degree of RF measurement accuracy.
The purpose of our testing services is not to provide a basis for contesting the siting of cell phone towers or to seek their removal once sited. This position is not the result of an alliance between EMF Services and the cellular service providers. They are not our clients. Rather, it represents an effort to avoid leading you down the path toward a disappointing result. The RF levels near a cell tower will not approach Maximum Permissible Exposures at ground level where people are present. Therefore, from a legal perspective, grounds for such an action do not exist. Further, a court of law is not the best venue for a challenge to the science on which existing standards are based. The likely result is disappointment and a wasted financial expenditure. The best reason for testing and measurement services is to understand the field levels that exist, and what can be done to reduce them.
Regulations adopted by the Federal Communications Commission (FCC) in 1996, and fully implemented in 2000, limit human exposure to electromagnetic radiation from cell phone, broadcast, and other radio communication systems. Both U.S. and international standards governing exposure to radio frequency (RF) fields have long existed, and the FCC regulations were adapted from a pre-existing standard. They establish Maximum Permissible Exposures, or MPEs, for the full range of frequencies encountered near transmitting equipment, towers, and antennas. These are the formal exposure standards in the U.S., and have full regulatory force.
For cellular antennas on towers, the level of RF energy that one would realistically be exposed to is usually less than 1% of the MPE. For broadcast towers and building mounted cellular antennas, much higher exposures are possible, although the MPEs are still unlikely to be exceeded in areas accessible to the public. So why are people concerned about cell towers, or RF exposure in general? Is some caution warranted? Three reasons for this concern are recognized:
Some people don't trust the cell phone companies or the government to act with the public's best interest in mind.
Many people equate the potential adverse health effects of cell phone use, which has received a lot of media coverage, with the presence of cell towers. (In reality, the energy that one is exposed to while holding a cell phone to the head is far greater than one is exposed to in the vicinity of a cell tower.)
The existing exposure limitations are based primarily on the avoidance of energy deposition in the body sufficient to cause heating of tissue. More recent research data indicates that some types of radio frequency fields influence cellular function through mechanisms that do not involve heating. Therefore, the existing limitations may be based upon incomplete and outdated science, and thus not fully protective.
To address the issues raised by recent health effects research (#3 above), it is necessary to look beyond the current exposure limits. Through a review of research on exposure to radio frequency radiation, it is possible to identify a range of numbers below which no adverse effects have been noted (or which have been reported only in limited or questionable studies), and above which potentially adverse effects have been seen. This range of numbers can form the basis for a "precautionary guideline." The science from which it is derived is not, at this time, sufficient in strength or consistency to permit the revision of existing standards. However, reference to such a precautionary guideline will permit those individuals who seek a level of protection beyond that conferred by existing standards to do so in a rational manner while research proceeds on this important public health issue.
Measurement of the emissions from cell towers presents particular technical challenges beyond those encountered for broadcast antenna sites. To understand these challenges, a few comments about radio frequency measurement are required.
Protocols for the measurement of RF energy for the purpose of human exposure assessment often recommend the use of an "isotropic broadband probe" because this type of sensor responds equally to energy arriving from any direction, and over a broad frequency range, as does the human body. These instruments are commonly used because they permit a quick and simple measurement. Unfortunately, some of the meters used for typical RF compliance surveys are unable to accurately measure the low power densities present at some cell sites. An alternate approach is required.
A related problem involves the concurrent presence of other signals besides those from the cell phone system. The "broadband" characteristic of the isotropic broadband probe means that it will measure any signals across a wide range of frequencies. The reading produced by the instrument will be the combination of all signals present. In a large number of cases, the other signals present near a cell tower will be as strong as the cellular signals that one is trying to measure. Realistically, this composite measurement of all signals may be the most relevant exposure metric, but an interpretation of the significance of a reading sometimes requires that one know the frequency of the signal that produced it. For instance, is it FM, TV, cellular, or something else?
One of the most significant RF measurement problems, and one responsible for some of the greatest inaccuracy, involves an instrument erroneous response that can occur when there are two or more strong signals present at the same time. A very large proportion of antenna sites (cell and broadcast) now have multiple strong signals. Instrument design can minimize this problem, but many of the commonly used isotropic broadband meters perform very poorly in this multi-signal environment. The result is a reading that is much higher than actual, sometimes double (100% error).
An additional challenge results from the fact that power density levels at a cell tower site are not always constant, as they usually are at a broadcast antenna site. People use their cell phones more at some times of the day, and on some days of the week, than at others. The cellular service providers maintain additional capacity in the form of multiple channels which will become active as needed to meet demand. Each active channel adds to the measured power density at the cell site. The variable nature of power density levels at some sites must be taken into account. When necessary, we employ timed signal averaging or data logging to produce an accurate assessment.
RF measurement surveys conducted by EMF Services employ procedures and equipment to address each of the challenges noted above. A spectrum analyzer is used for identification of RF sources, and for assessment of the relative magnitude of signals in different frequency ranges. The use of this instrument with a calibrated antenna will allow a sensitive and precise "channel power measurement" across selected frequency ranges, or measurement of the strength of an individual broadband signal. This completely eliminates the problem of inaccuracy in the presence of multiple strong signals. It also permits a determination of the amount of power that is present in different parts of the RF spectrum, such as FM radio, TV, cellular, etc. Another benefit of spectrum analysis is the ability to identify the cellular carriers that are present at a site. Our comprehensive analytical report summarizes all this data in a concise and understandable format, but includes an Appendix with detailed site data, such as the spectrum analyzer plots shown below.
Most people recognize that the most extreme position on any issue is seldom the best. Likewise, the lowest exposure guideline number is not necessarily the best number. At the far extreme, we could all be advised to live in a welded steel box with no windows and a leakproof RF door. How practical is that, and how good would that quality of life be? It is time we allowed reason to prevail over fear.
We are sometimes presented with questions about the guidelines referenced by other organizations. The frequency at which this occurs has prompted the following comments about the guidelines being used by some groups:
There is no stated scientific basis for the recommended levels. They seem to be derived from what a small group of people (possibly one person) felt were best, based on personal experience. In at least one case, they were based upon the lowest displayable level on the instrument that their practitioners are advised to use. Such recommendations are neither objective nor scientifically verifiable, and should not be generalized to whole populations. This is an example of how science should not be done.
The range of levels in different categories, ranging from lowest to highest exposure, appear to be completely arbitrary as there is no supportable explanation for this stratification, such as a rising risk curve or dose-response ratio in any type of study.
The lowest recommended exposure level is often unachievable in a typical suburban or urban environment without shielding the building, or at least shielding specific rooms of the building. Any recommendation which implies that most people in the world today are living in a hazardous environment should be considered suspect. At the best, it is fear-mongering that fosters the development of phantom illness. Most practitioners in this field are fundamentally responsible and highly ethical people who are committed to making a positive difference in their clients' lives, but reliance on a standard with no discernible scientific basis threatens their legitimacy.
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