Microwave radiation: level of acceptable exposure subject of wide disagreement SARAH HENRY
Some call it electronic smog. Others tary ones (using US recommended have dubbed it "the air pollution you levels) set by the Canadian Standards can't see Association. Whatever. Microwave radiation is But at the 1978 symposium on fast becoming the most hotly debated electromagnetic fields in biological and complex environmental health systems in Ottawa June 27 to 30, issue to come along in years. It began federal officials told visiting scientists as mild concern about the potential they believe it is time to propose the dangers of microwave ovens and has first government standards for limitrapidly escalated into vocal opposi- ing microwave exposure. tion from a number of consumer The symposium was one of four groups about the dangers of non-ion- microwave-related conferences held izing radiation in all its manifesta- over the course of the week, which tions. brought together about 1000 microwave researchers, the largest international gathering to be held anywhere It's everywhere this year. And there's no getting away from The proposed federal health standit. It's everywhere. ard is only 10% that of the existing Almost all communications sys- 100 W/m' recommended level. But tems emit microwave radiation - even 10 W/m2 is many times higher television and radio transmitters, taxi than the exposure most of the popudispatch lines, civilian and military lation will ever encounter. radar installations, long-distance teleThe new standard will likely be phones, burglar alarms, police radar put forward as a labour safety standtraps and the increasingly popular ard. The power density will be citizens' band radios. Microwave coupled with this formula: radiation has found its way into a 60 variety of industries for its powerful heating and drying effects. T Microwave radiation at extremely high power densities has been linked P is the acceptable power density to the formation of cataracts, heart and T is the number of minutes exdisease, cancer, central nervous sys- posure time per hour. tem disorders, genetic damage and The health department is calling changes in the blood brain barrier. for comments on the proposals from But scientists remain in disagree- scientists and industry before recment about the levels at which dan- ommending adoption to the federalger occurs, though all agree it is hard provincial committee on radiation to find conclusive evidence that harm surveillance. If accepted, the procan occur at the low radiation levels posals would then go to the conferthe population experiences. ence of deputy ministers before being Until now, our only maximum ex- passed on to provincial governments, posure guidelines have been volun- which could set legislative standards
on Canadian microwave industries. The recommendations won strong approval from scientists and microwave experts attending the conference, most of whom agree some checks should be put on rapidly expanding microwave technology. "Probably 99.9% of the population of North America is exposed to about 1000 times less than the recommended proposal," said federal health protection branch radiologist Michael Repacholi. Future problems But projects like the US solar satellite power station, a prototype of which may be aloft within the decade, could pose future problems, he said. The SSPS would translate sunrays into microwave radiation and beam the energy to receiving stations on earth. On the way, some radiation dispersal is inevitable, subjecting large portions of the population to additional exposure. "Present tabulations suggest people would not receive more than one or two microwatts," said Mr. Repacholi. "But the purpose of the proposed standard is to provide guidelines for these sorts of projects so they know they have to stay within them." The proposed standard also adjusts maximum levels for occupational exposure to 10 W/m', under the same frequency conditions that apply to the general population. Exposure of up to 50 W/m' would be permitted within a narrower frequency range. Although existing voluntary exposure standards are considered safe
CMA JOURNAL/AUGUST 26, 1978/VOL. 119 367
by most yardsticks, they are still 1000 times higher than legal maximums in the Soviet Union. The western philosophy for setting standards has been based on the assumption that the only potentially hazardous effect of microwave radiation is a heating effect while Soviet scientists have long believed there are effects - though not necessarily hazardous ones - at levels lower than the North American recommended maximums. The tightening of Canadian standards (the US is expected to make similar adjustments to recommended levels next year) is viewed as an acceptance that there is sufficient doubt about the effects of low-level exposure to warrant additional caution until research proves otherwise. Controversy While scientists disagree on the threshold levels and frequencies at which serious health problems may develop, even more controversial is Soviet research describing the neurasthenic syndrome. A number of epidemiologic and animal studies have suggested that extremely low levels - lower even than the proposed Canadian standards - can prompt reversible behavioural changes like apathy, fatigue, headache, insomnia, impotence and loss of libido. Until recently, US and Canadian researchers have been unable to replicate the animal studies or find any epidemiologic evidence within microwave industries that such changes can occur. Many North American microwave biologists are highly sceptical about the Soviet claims. However, researchers attending the Ottawa symposium heard a University of Washington medical department group describe the first successful western attempt to see the same behavioural changes described in Soviet studies. Rats exposed to radiation levels one 20th those of human exposure standards at microwaveoven frequencies became lethargic, forgetful, and didn't react to shock as readily as the control group. Dr. Richard Lovely, a biopsychologist working on the project, described the results as "provocative" but cautioned that the Washington researchers and other US groups must repeat the experiment before making final judgements.
Eight rats were exposed 7 h/d for 3 months. By the end of the period, the irradiated rats required higher levels of shock before they would react, they didn't move about their cages or engage in the "rearing" activity characteristic of rats and were unable to remember a shock avoidance task they had learned the month before, Lovely said. A month following the experiments, these behaviour changes disappeared. To parallel the effects of exposure in rats, human beings require about four times the microwave power density, but Dr. Lovely cautioned it is too early in the study to speculate on the effects of low-level radiation on human subjects. Biochemical changes in enzyme production observed in the Soviet studies were only partially duplicated by the US group, although studies on electrolytes showed the rats developed high sodium and low potassium levels. After the rats were sacrificed, the scientists found the only organs that showed any abnormality were the adrenals, which received the most immediate exposure to the nonionizing radiation. Further evidence was also presented by a US microwave researcher showing cataracts did not develop in rabbits exposed to high microwave levels daily over long periods. "We looked at levels way above those the US or Canadian governments consider hazardous," Dr. Russell Carpenter, a consultant to the US bureau of radiological health, said. "The lowest level we have been able to find cataracts at on a cumulative basis is 1800 W/m2 for 1 h/d for 20 consecutive days." Dr. Carpenter said his group also did a study in which rabbits were placed in front of a microwave oven deliberately altered to leak at a power density of 100-120 W/m'. After a 1 h exposure every day for 12 weeks, "their eyes were just as clear as they were before." Carpenter's work suggests cataracts will form only at microwave radiation levels high enough to heat the rabbit's eye a couple of degrees Celsius. The fact that heat will produce cataracts has long been known, he pointed out; glassblowers and workers dealing with molten lead were long ago identified as facing a particular risk to their eyes.E
368 CMA JOURNAL/AUGUST 26, 1978/VOL. 119
Cortisporin Otic Drops A leader in the field of otological therap
.Cortispori fl: Otic Drops (Polymyxin B-Neomycin-Hydrocortisone) Sterile
INDICATIONS: External otitis, otitis media with perforated tympanic membrane, infections of mastoidectomy and fenestration cavities. .ONTRAINDICATIONS: This product is contraindicated in tuberculous, fungal or viral lesions (herpes simplex, vaccinia and varicella) alsointhose individuals who have shown hypersensitivity to any of its components. CAUTION: This product should be used with care in cases of perforated ear drum and in long-standing cases of chronic otitis media, because of the danger of ototoxicity. As with any antibiotic preparation, prolonged use may result in the overgrowth of non-susceptible organisms, including fungi. Appropriate measures should be taken if this occurs. DOSAGE: 3 or 4 drops in ear 3 to 4 times daily or more frequently in acute conditions if required. SUPPLIED: Each ml contains: polyrrryxin B sulfate 10,000 units, neomycin sulfate 5 mg, hydrocortisone 10 mg (1%) in sterile aqueous suspension. Available in 7 ml plastic dropper bottles. Also available: CORTISPORIN Ointment 3.5 g tube. Additional product information available on request.
.CaImic Limited LaSalle, Que. PAAB
.Trade Mark
.
C.6011
Some call it electronic smog. Others tary ones (using US recommended have dubbed it "the air pollution you levels) set by the Canadian Standards can't see Association. Whatever. Microwave radiation is But at the 1978 symposium on fast becoming the most hotly debated electromagnetic fields in biological and complex environmental health systems in Ottawa June 27 to 30, issue to come along in years. It began federal officials told visiting scientists as mild concern about the potential they believe it is time to propose the dangers of microwave ovens and has first government standards for limitrapidly escalated into vocal opposi- ing microwave exposure. tion from a number of consumer The symposium was one of four groups about the dangers of non-ion- microwave-related conferences held izing radiation in all its manifesta- over the course of the week, which tions. brought together about 1000 microwave researchers, the largest international gathering to be held anywhere It's everywhere this year. And there's no getting away from The proposed federal health standit. It's everywhere. ard is only 10% that of the existing Almost all communications sys- 100 W/m' recommended level. But tems emit microwave radiation - even 10 W/m2 is many times higher television and radio transmitters, taxi than the exposure most of the popudispatch lines, civilian and military lation will ever encounter. radar installations, long-distance teleThe new standard will likely be phones, burglar alarms, police radar put forward as a labour safety standtraps and the increasingly popular ard. The power density will be citizens' band radios. Microwave coupled with this formula: radiation has found its way into a 60 variety of industries for its powerful heating and drying effects. T Microwave radiation at extremely high power densities has been linked P is the acceptable power density to the formation of cataracts, heart and T is the number of minutes exdisease, cancer, central nervous sys- posure time per hour. tem disorders, genetic damage and The health department is calling changes in the blood brain barrier. for comments on the proposals from But scientists remain in disagree- scientists and industry before recment about the levels at which dan- ommending adoption to the federalger occurs, though all agree it is hard provincial committee on radiation to find conclusive evidence that harm surveillance. If accepted, the procan occur at the low radiation levels posals would then go to the conferthe population experiences. ence of deputy ministers before being Until now, our only maximum ex- passed on to provincial governments, posure guidelines have been volun- which could set legislative standards
on Canadian microwave industries. The recommendations won strong approval from scientists and microwave experts attending the conference, most of whom agree some checks should be put on rapidly expanding microwave technology. "Probably 99.9% of the population of North America is exposed to about 1000 times less than the recommended proposal," said federal health protection branch radiologist Michael Repacholi. Future problems But projects like the US solar satellite power station, a prototype of which may be aloft within the decade, could pose future problems, he said. The SSPS would translate sunrays into microwave radiation and beam the energy to receiving stations on earth. On the way, some radiation dispersal is inevitable, subjecting large portions of the population to additional exposure. "Present tabulations suggest people would not receive more than one or two microwatts," said Mr. Repacholi. "But the purpose of the proposed standard is to provide guidelines for these sorts of projects so they know they have to stay within them." The proposed standard also adjusts maximum levels for occupational exposure to 10 W/m', under the same frequency conditions that apply to the general population. Exposure of up to 50 W/m' would be permitted within a narrower frequency range. Although existing voluntary exposure standards are considered safe
CMA JOURNAL/AUGUST 26, 1978/VOL. 119 367
by most yardsticks, they are still 1000 times higher than legal maximums in the Soviet Union. The western philosophy for setting standards has been based on the assumption that the only potentially hazardous effect of microwave radiation is a heating effect while Soviet scientists have long believed there are effects - though not necessarily hazardous ones - at levels lower than the North American recommended maximums. The tightening of Canadian standards (the US is expected to make similar adjustments to recommended levels next year) is viewed as an acceptance that there is sufficient doubt about the effects of low-level exposure to warrant additional caution until research proves otherwise. Controversy While scientists disagree on the threshold levels and frequencies at which serious health problems may develop, even more controversial is Soviet research describing the neurasthenic syndrome. A number of epidemiologic and animal studies have suggested that extremely low levels - lower even than the proposed Canadian standards - can prompt reversible behavioural changes like apathy, fatigue, headache, insomnia, impotence and loss of libido. Until recently, US and Canadian researchers have been unable to replicate the animal studies or find any epidemiologic evidence within microwave industries that such changes can occur. Many North American microwave biologists are highly sceptical about the Soviet claims. However, researchers attending the Ottawa symposium heard a University of Washington medical department group describe the first successful western attempt to see the same behavioural changes described in Soviet studies. Rats exposed to radiation levels one 20th those of human exposure standards at microwaveoven frequencies became lethargic, forgetful, and didn't react to shock as readily as the control group. Dr. Richard Lovely, a biopsychologist working on the project, described the results as "provocative" but cautioned that the Washington researchers and other US groups must repeat the experiment before making final judgements.
Eight rats were exposed 7 h/d for 3 months. By the end of the period, the irradiated rats required higher levels of shock before they would react, they didn't move about their cages or engage in the "rearing" activity characteristic of rats and were unable to remember a shock avoidance task they had learned the month before, Lovely said. A month following the experiments, these behaviour changes disappeared. To parallel the effects of exposure in rats, human beings require about four times the microwave power density, but Dr. Lovely cautioned it is too early in the study to speculate on the effects of low-level radiation on human subjects. Biochemical changes in enzyme production observed in the Soviet studies were only partially duplicated by the US group, although studies on electrolytes showed the rats developed high sodium and low potassium levels. After the rats were sacrificed, the scientists found the only organs that showed any abnormality were the adrenals, which received the most immediate exposure to the nonionizing radiation. Further evidence was also presented by a US microwave researcher showing cataracts did not develop in rabbits exposed to high microwave levels daily over long periods. "We looked at levels way above those the US or Canadian governments consider hazardous," Dr. Russell Carpenter, a consultant to the US bureau of radiological health, said. "The lowest level we have been able to find cataracts at on a cumulative basis is 1800 W/m2 for 1 h/d for 20 consecutive days." Dr. Carpenter said his group also did a study in which rabbits were placed in front of a microwave oven deliberately altered to leak at a power density of 100-120 W/m'. After a 1 h exposure every day for 12 weeks, "their eyes were just as clear as they were before." Carpenter's work suggests cataracts will form only at microwave radiation levels high enough to heat the rabbit's eye a couple of degrees Celsius. The fact that heat will produce cataracts has long been known, he pointed out; glassblowers and workers dealing with molten lead were long ago identified as facing a particular risk to their eyes.E
368 CMA JOURNAL/AUGUST 26, 1978/VOL. 119
Cortisporin Otic Drops A leader in the field of otological therap
.Cortispori fl: Otic Drops (Polymyxin B-Neomycin-Hydrocortisone) Sterile
INDICATIONS: External otitis, otitis media with perforated tympanic membrane, infections of mastoidectomy and fenestration cavities. .ONTRAINDICATIONS: This product is contraindicated in tuberculous, fungal or viral lesions (herpes simplex, vaccinia and varicella) alsointhose individuals who have shown hypersensitivity to any of its components. CAUTION: This product should be used with care in cases of perforated ear drum and in long-standing cases of chronic otitis media, because of the danger of ototoxicity. As with any antibiotic preparation, prolonged use may result in the overgrowth of non-susceptible organisms, including fungi. Appropriate measures should be taken if this occurs. DOSAGE: 3 or 4 drops in ear 3 to 4 times daily or more frequently in acute conditions if required. SUPPLIED: Each ml contains: polyrrryxin B sulfate 10,000 units, neomycin sulfate 5 mg, hydrocortisone 10 mg (1%) in sterile aqueous suspension. Available in 7 ml plastic dropper bottles. Also available: CORTISPORIN Ointment 3.5 g tube. Additional product information available on request.
.CaImic Limited LaSalle, Que. PAAB
.Trade Mark
.
C.6011
