'Diluted' Measurements Are Used To Give NEXRAD a Clean Bill of Health

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The radar signal from NEXRAD will be thousands of times greater than what current standards allow. However, by using an “averaged” value for the signal’s emissions, NEXRADs proponents claim that no harm will come from exposure to the beam.

Peak Power

In 1991, the Institute of Electronic and Electrical Engineers adopted standards for human exposure to radio-frequency radiation. For electrical fields having frequencies of 2700 to 3000 MHz (2.7 to 3 million cycles per second), the IEEE recommended limits for public exposure are 1.8 to 2.0 mW/cm2. By contrast, standards promulgated by the former Soviet Union are far more stringent. In the NEXRAD frequency range, the Soviet exposure limit is 0.01 m W/cm2 – or one one-thousandth the power density of a NEXRAD beam at a distance of two miles.

The duration of the pulses emitted by NEXRAD is, in most cases, extremely short – measured in microseconds. This means that even at the peak pulse frequency rate (up to 1,300 pulses per second), the actual percentage of time when electrical fields will be emitted by a NEXRAD system is less than two-tenths of one percent.

Because of this, the time-averaged power densities associated with NEXRAD are thousands of times lower than the peak power densities. The consultants hired to prepare the environmental and health studies on NEXRAD’s potential effects tend, therefore, to speak almost always in terms of time averaged exposures, rather than peak exposures. Indeed, in the Environmental Assessment prepared for the Moloka’i NEXRAD, no mention is made whatsoever of the peak power densities. Instead, the consultants – SRI International – write: “When a NEXRAD antenna is at its lowest practical height, the highest average power density RF [radio frequency] radiation to which the general public will be exposed is expected to be 0.003 mW/cm2 – more than a factor of 600 lower than the current U.S. standard.”

‘Diluted’ Measurements

This is not the first time that “time-averaged” exposures have been used to minimize the potential health effects of a radar installation. Writing in The New Yorker of June 19, 1989, Paul Brodeur describes the attempt of the Air Force to assuage public worries that an Air Force radar system, called PAVE PAWS,1 proposed for Cape Cod, Massachusetts, might harm people living nearby (It is worth noting that the consulting firm hired to prepare the Air Force’s EIS was SRI International.) Brodeur writes that in August 1979, John C. Mitchell, chief of the radiation sciences division of the Air Force’s School of Aerospace Medicine “and an Air Force survey team, along with civilian monitors, set out to measure microwave-radiation levels emanating from the partly completed Cape Cod PAVE PAWS radar. The Air Force survey team diluted its measurements, however, by time-averaging the power density of the microwave radiation; that is, the team included in its calculations the intervals between the radar’s short pulses, with the result that the average power calculated was only a small fraction of the peak pulse power. This expedient allowed the Air Force to say that it was adhering to the recommended standard for exposure to microwave radiation, of ten milliwatts per square centimeter,2 which was based upon the obsolete notion that its only harmful effect was the heat it could create in the body if it was generated at high power.”

History Lessons

In the EIS for PAVE PAWS, according to Brodeur, the Air Force and SRI International were dismissive of studies indicating a possible link between the type of microwave radiation emitted by the PAVE PAWS radar and health effects other than that of heating. (A propos of the Air Force’s health standard based on the heating properties of microwave radiation, Brodeur writes: “Skeptics who had watched the Air Force pull this stunt time and again over the years called it the English-muffin standard, because of the implication that microwave radiation was harmless as long as you didn’t turn brown or feel toasty.”)

SRI’s “Supplemental Environmental Assessment of the Effects of Electromagnetic Radiation from the WSR-88D Radar”3 is similarly dismissive of studies suggesting that microwave or radio frequency radiation might harm health. This should not be surprising. Appendix B to the Supplemental EA, titled “Human Health Effects of RFR,” contains the statement: “Some of the analyses and critiques here of papers published before 1987 have been derived from a general review entitled: Critique of the Literature on Bioeffects of Radiofrequency Radiation: A Comprehensive Review Pertinent to Air Force Operations,” which was prepared by L.N. Heynick of SRI International, under contract to the Air Force, following the PAVE PAWS controversy.

Accentuating the Negative

In Appendix B, SRI International runs through the list of suspected health effects. These include thermal and non-thermal “interactions,” with the latter category by far the more interesting.

There is, for example, the auditory “interaction” – the possibility that people exposed to a NEXRAD pulse might hear it manifested as a loud sound. “Some researchers regard these reports” (of auditory effects) “as evidence of potentially harmful nonthermal RFR bioeffects. There is no experimental evidence that the RFR auditory effects is [sic] harmful to humans or animals.”

Some studies indicate that RFR can promote tumor growth. Others suggest RFR exposure can influence the rate at which calcium ions bind to or separate from brain cells (a phenomenon described as calcium efflux) while still more indicate cell membrane functions may be affected by weak electrical and magnetic fields.

Heart disease and eye damage are among other effects investigated in still more studies.

Almost invariably however, SRI International disparages the studies that point to a positive association between nonionizing electromagnetic radiation (including radiofrequency radiation) and impacts on human health, while accentuating those studies that cast doubt on such links.

A Lack of Balance

To a letter dated May 26, 1992, Richard E. Sanderson, director of the EPA’s Office of Federal Activities, attached 14 pages of specific criticisms of SRI’s Supplemental Environmental Assessment. Appendix B, containing the most detailed discussion of scientific studies on health effects, “offers several areas that need to be changed for a more balanced presentation,” Sanderson wrote even though he agreed that, “given the current data on biological effects of pulsed RFR, there is no known health hazard from WSR-88D Radar (formerly known as NEXRAD).”

SRI prepared draft responses to the 79 specific points Sanderson raised and allowed the EPA to comment once more on the draft. In a letter dated October 8, 1992, the EPA’s Health Effects Research Laboratory listed its comments on those draft responses. While many were deemed satisfactory, serious disagreements remained in several significant areas. For example, the EPA reviewers were not pleased that SRI dismissed altogether studies on calcium efflux (a decision based, SRI stated, on a lack of observed health effects).

Sanderson had objected to the heavy reliance of the Supplemental EA upon SRI’s own Critique of the Literature on Bioeffects of Radiofrequency Radiation, a document that, he noted, “has not been subjected to peer review.” He continued: “The use of the Critique has contributed to errors of omission and commission that should be corrected before the SEA can be accepted as a comprehensive and objective review of the literature.” SRI responded by noting that its study “was critically reviewed by RFR-bioeffects researchers at the U.S. Air Force School of Aerospace Medicine” and that the study “has served as the primary reference on RFR bioeffects for the EISs or EAs of a number of Air Force radar systems (e.g., PAVE PAWS, OTH-B) reviewed by interested members of the public and various governmental agencies, including EPA.”

Errors of Omission, Commission

In its return volley of October 8, 1992, the EPA wrote: “We accept your statement that the Heynick (1987) document was reviewed by RFR-bioeffects researchers at the U.S. Air Force School… but this type of intramural review of a contractor’s report does not equate to peer review… Our position is unchanged. The use of the 1987 report contributed to errors of omission and commission that should be corrected before the SEA can be accepted as a comprehensive and objective review of the literature.”

SRI International had the last word; the final Supplemental EA continues to rely heavily on the previous SRI study and, apart from a few minor changes, the emphasis remains on studies showing no correlation between health effects, while contrary findings are criticized as flawed, inconclusive, and the like.

But at least on this criticism, the EPA stood its ground. On an even more fundamental comment that the format be reorganized the EPA pulled back. In its October comments, it stated: “Recommendation to reorganize draft SEA withdrawn because of the need to complete the final SEA as quickly as possible.”

On several other points, too, the EPA reviewers seem to accept defeat, issuing cautions that SRI seems to have ignored in the final Supplemental EA. For example, the EPA reviewers state: “To be judged an objective report, again in regard to RF radiation, the report cannot give the wrong impression that all RF epidemiologic studies are badly done and report negative effects. And, “The authors of the SEA will make a major error in judgment if they do not incorporate the conclusions of the EPA Science Advisory Board… and the Advisory Croup on Nonionizing Radiation to the UK… The interpretations of the literature by these two expert panels are essential to the conclusions drawn in the SEA.” (The final Supplemental EA does not incorporate these suggestions.)

1 Short for Precision Acquisition of Vehicle Entry Phased Array Warning System.
2 The standard has since been made more stringent, as mentioned earlier.
3 WSR-88D is the new name for NEXRAD, standing for Weather System Radar – 88D (with the D presumably standing for Doppler.)

Volume 4, Number 4 October 1993

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