Value chain · CLM-1155
In plain terms
The 1978 reviewers did the sum for a small bird flying four kilometres through the beam centre and concluded it would probably die of heat, on rat data and the physics of a bird the size of half a wavelength; nobody had flown a bird through a continuous beam to find out.
The claim as recorded
The 1978 PNL review reasoned that a bird crossing the reference beam would probably not survive: "the power density of the microwave beam will be at least 20 mW/cm2 within an approximate 2-km radius of the rectenna" centre, so "A bird that attempted to fly along a path through the center of the beam would travel a distance of nearly 4 km through fields within which rates of energy absorption could double or treble because of resonance", a 5 cm bird aligned with the E-field being "resonant in a 2450-MHz field" and effectively "exposed to radiation at a power density in excess of 50 mW/cm2", and "Even neglecting the factor of resonance, it is doubtful that an animal could survive such a flight because of the added thermal burden"; the rodent basis is a free-field lethal range of "50 to 500 mW/cm2", rats that "expired within two hours while exposed to radiation at a power density of 30 mW/cm2" under restraint, and convulsive doses "between 22 and 30 J/g" at 25-210 mW/g; while "no experimental studies have been reported on effects of unmodulated microwaves on birds in flight" and whether a bird would sense and avoid the beam "are open questions".
Evidence behind this: T3-the reviewers' own hazard reasoning from cited rodent dosimetry and the beam geometry; the lethal figures are the cited studies', the bird inference is the review's.
Scope and limits
AN INFERENCE, NOT A MEASUREMENT: the review says so ("doubtful", "open questions"), the lethal figures are for restrained rats and mice in cavities and free fields, and the resonance argument assumes E-field alignment. The honey-bee programme (SRC-537, CLM-1150 and CLM-1152) later found insects unaffected at up to 50 mW/cm2 for 30 minutes and willing to enter 40 mW/cm2; the bird case was addressed by SRC-454 (1984) and the 1980 assessments, which the register should read against this row rather than treat this row as the finding.
What it assumes
The Bloomquist 1976 beam profile (20 mW/cm2 out to 2 km) as cited; rodent thermal tolerance as a guide to avian.
Where it comes from
PDF 41 / printed 34 (render read): "As currently projected, the power density of the microwave beam will be at least 20 mW/cm2 within an approximate 2-km radius of the rectenna" (normalised); "A bird that attempted to fly along a path through the center of the beam would travel a distance of nearly 4 km through fields within which rates of energy absorption could double or treble because of resonance, i.e., a small avian with a long axis that approximates 5 cm would, given parallel alignment to the vector of the E-field, be resonant in a 2450-MHz field" (normalised); "Even neglecting the factor of resonance, it is doubtful that an animal could survive such a flight because of the added thermal burden" (normalised). PDF 44 / printed 37 (render read): "the extrapolated range of power densities that corresponds to the range of dose rates of Phillips, et al. is 50 to 500 mW/cm2" (normalised); "Under restraint, the animals expired within two hours while exposed to radiation at a power density of 30 mW/cm2" (normalised); "with a long axis near five centimeters, effectively will be exposed to radiation at a power density in excess of 50 mW/cm2" (normalised). PDF 43 / printed 36: "convulsive doses ranged narrowly between 22 and 30 J/g for latencies that ranged between 100 and 1200 sec" (normalised); "the averaged dose to convulsion for a normal rat under standard environmental conditions is near 25 J/g, given a dose rate of 100 mW/g" (normalised); "a mouse irradiated in a 2450-MHz field at l mW/cm2 would accumulate a 25-J/g dose after six to seven hours, but no untoward heating would occur" (normalised, the page's "l"); "At lower power densities and longer durations of exposure, the predictive value of the energy-dose number breaks down" (normalised). PDF 39 / printed 32: "no experimental studies have been reported on effects of unmodulated microwaves on birds in flight" (normalised); parakeets under "9300-MHz pulsed radiations (40-mW/cm2 average, 4-W/cm2 peak) produced aversive behaviors" (normalised). PDF 42 / printed 35: "no controlled experiments that bear on aversive behaviors of airborne avians in a CW field have been reported" (normalised); "Whether the airborne avian possesses a fine thermal sensitivity, and whether such a sensitivity, if present, would be used to avoid excessive radiation, are open questions" (normalised). Recomputed: 2 x 2 km = 4 km; 25 x 2 to 3 = 50-75 mW/cm2; a 4 km crossing at 10 m/s takes 400 s, inside the 100-1200 s convulsive latencies quoted for 25-210 mW/g, a comparison this record makes and the review does not.
Basis: mW/cm2; km of beam; J/g and mW/g absorbed dose; cm of body length
Cite this
energyaperture.com/c/clm-1155
CLM-1155, Energy Aperture, as of 1978-05.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-557
- CLM-1154In 1978 the literature said the fence-line level was well below anything known to cause disease over the short term, that no study had come...CLM-1156The one worrying result at the fence-line level in 1978 was thinner eggshells in hens kept twelve weeks in a metal cage whose field...CLM-1157The reviewers said most of the older microwave-health literature could not be trusted on how much power the animals actually got, that...