RF RADIATION—
FACTS AND FALLACIES
Ken Joyner*
Electromagnetic Compatibility Section
Telecom Australia Research Laboratories
Victoria
THE DEBATE OVER POSSIBLE ADVERSE HEALTH EFFECTS FOLLOWING exposure
to electromagnetic radiation (EMR) is very controversial and very much to the
fore in Australia today.
The Sir Harry Gibbs Inquiry into Community Needs and High Voltage
Transmission Line Development in New South Wales and the debate on siting of the
Richmond/Brunswick power line in Victoria have received a great deal of media
attention.
EMR is a generic term and refers to the transport of energy in the form of an
electromagnetic wave travelling at the speed of light. The EMR spectrum is very wide
and covers power frequency fields, radio-frequency and microwave, infrared, visible,
ultraviolet, X-ray and some nuclear radiations. (Note that, in the context of this paper,
microwave radiation will be regarded as a subset of the radiofrequency (RF) band.)
Claims of adverse health effects due to EMR exposure include increased cancer
rates, adverse pregnancy outcomes and cataract induction.
Insofar as police and law enforcement personnel are concerned, a possible risk
due to exposure to EMR, over and above that of the general community, may arise
because of the use of RF transmitting devices during the course of their employment.
In addressing the issue of increased risk of adverse health effects arising from
exposure to RF, this paper shall draw heavily from the experiences of Telecom
Australia, which is the largest user of RF radiation in Australia outside of the Defence
Department. As such, Telecom Australia has a large number of people involved in the
use and transmission of RF radiation with transmit powers as low as a few milliwatts
up to several hundred kilowatts. A detailed discussion of the health risk management
of RF radiation may be found elsewhere (see Hocking & Joyner 1991).
*
I wish to express my thanks to Dr Trevor Boal and Mr Morrie Facci from the Victorian
Health Department for much of the information on exposure levels from police radio
equipment. The permission of the Executive General Manager, Telecom Research
Laboratories, to publish this paper is hereby acknowledged.
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Australian RF Exposure Standard
The allowable RF exposure limits in Australian Standard AS2772.1–1990 are shown
in Figure 1.
Figure 1
Australian Standard AS2772.1–1990
Source: Standards Australia 1991, Australian Standard
AS2772.1 Radio Frequency Radiation, Part 1: Maximum
Exposure Levels, 100 kHz–300 GHz.
Several points about the Australian Standard are worthy of note.
•
The time over which the measured RF level is to be averaged is sixty
seconds. Obviously if an exposure takes longer than sixty seconds then the
measured level is compared directly to the limit value. However, if an
exposure takes only thirty seconds then the time-averaged exposure level is
half of the measured level. For pulsed or intermittent RF sources, the timeaveraged exposure level is found by multiplying the measured RF level by
the duty cycle of the source. The duty cycle is the ratio of the time the RF
source is on to the time it is both on and off.
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RF Radiation — Facts and Fallacies
•
The exposure limits for the community are set at one-fifth of the lowest
occupational levels in recognition of the fact that the general community
encompasses babies, old people, sick and infirm persons and, those who, by
virtue of living next to a transmitter site, may be exposed to the radiation for
up to 24–hours a day.
•
There is an exclusion clause in the Standard which exempts from compliance
all devices which have output powers of less than 7 W and transmit
frequencies of less than 1000 MHz.
Health Studies on Exposed Populations in Australia
Telecom Australia has conducted or contributed to two studies of the health status of
its workforce. These are:
•
All cases of neoplasms of the blood leading to invalidity retirement for the
period 1 July 1976 to 30 December 1982 from the Australian Public Service
and Telecom were obtained from the Australian Government Retirement
Benefits Office. There were 119 cases of which twenty-five (21 per cent)
involved Telecom staff. Of the 287,614 contributors, 28 per cent were
Telecom staff. Analysis of the twenty-five Telecom cases did not show an
over-representation of any work designation for leukaemia. Within the
limitation of this study there is no evidence of Telecom operations causing an
excess of leukaemia cases in staff (Hocking 1984).
•
Chromosome studies were performed on blood samples from thirty-eight
radio-linemen matched by age with thirty-eight controls, all of whom were
employed by Telecom Australia. The radio-linemen had all worked with RF
radiation in the range 400 kHz to 20 GHz with exposures at or below the
occupational limits in the Australian Standard. The controls were members of
the clerical staff who had no known exposure to RF radiation. Two hundred
metaphases from each subject were studied and chromosome damage was
scored by an observer who was blind to the status of the subjects. The ratio
of the rate of aberrant cells in the radio-linemen group to that in the control
group was 1.0 (95 per cent confidence interval, 0.8–1.3). There were no
statistically significant differences in the types of aberrations that were
scored. It was concluded that exposure to RF radiation at or below the limits
in the Australian Standard did not appear to cause any increase in
chromosomal damage in circulating lymphocytes (Garson et al. 1991).
Another study, independent of Telecom, was carried out by Hollows & Douglas
(1984) who investigated the incidence of lens opacities in the eyes of Telecom radiolinemen. Hollows and Douglas examined with a slit-lamp the lenses of Telecom radiolinemen and age-matched controls. The exposed sample consisted of persons who had
worked for fifteen or more years as radio-linemen and were over forty-five years of
age but less than sixty years of age. The controls were mail sorters. The results of this
study found that posterior subcapsular opacities occurred in 21 per cent of radiolinemen and 8 per cent of controls.
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It is of interest to note that mail sorters require particularly good vision. In
addition, a recent litigation case in Australia for cataract induction from occupational
exposure to microwave radiation was lost by the applicant. The Administrative
Appeals Tribunal found that:
On the balance of probabilities, it is probable that the applicant’s exposure to
microwave radiation did not cause, or accelerate the development of, the cataracts or
contribute to doing so (Joyner 1989, p. 548).
Exposure Measurements
Table 1 contains measurements of typical exposures for specific classes of equipment
in use by police and law enforcement personnel in Australia. Many of the radios are
not operated continuously and typically have a duty cycle of around 5 per cent. To
find the time averaged exposure level the measured level should therefore be
multiplied by 0.05.
As a general rule of thumb, for devices transmitting around 100 W a separation
distance of 60 cm (an arm’s length) is required to achieve compliance with the
Australian Standard. Where possible, vehicular antennas should be located as far as
practicable from occupants. Covert antennas should not be located in the head rests of
vehicles.
Portable radios
Close to the antennas of devices operating below 1000 MHz and with output powers
of less than 7 W, the measured levels can exceed the occupational exposure limits in
the Australian Standard.
Even though these devices are exempt from compliance, questions have been
asked about the legitimacy of the exemption given that exposure levels may exceed
the limits. Very recent work at Telecom Research Laboratories has shown that the
underlying basis for the exclusion clause is scientifically based and little or no thermal
response is elicited in operators of exempt portable RF devices (Joyner 1989).
Portable radios that are not covered by the exclusion clause, such as high power
backpack units, have to be treated on a case by case basis but, in general, the duty cycle of
typical transmissions needs to be taken into account.
Radio maintenance
Technicians maintaining radio equipment should minimise exposures through the use
of dummy loads and safe work procedures. Maintenance personnel should be involved
in the formulation of the safe work procedures.
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RF Radiation — Facts and Fallacies
Table 1
Typical Exposure Levels for Specific Equipment Classes
Measured Exposure Level
Relative To Limit
Equipment Type
Antenna Mounting
FALCOM Speed Radar
Gun (24.15 GHz;
10–40mW)
Hand Held
0.4 @ 5 cm from aperture
0.3 through car windscreen
not detected behind unit
UHF Radio (25 W)
Rear parcel shelf
of vehicle
1.3 @ head of rear passenger
(25 cm dist.)
0.13 @ head of driver
0.53 @ 40 cm outside of car
adjacent rear door
0.19 @ 60 cm outside of car
adjacent rear door
UHF Radio (25W)
Police motorcycle
above rear wheel
0.7 @ rider's head
0.35 @ rider's waist
2.1 @ 15 cm from antenna
VHF Radio (20 W)
Police motorcycle
above rear wheel
0.2 @ rider's head
0.13 @ rider's waist
4.0 @ 15 cm from antenna
UHF Radio (50 W)
Standard car radio
antenna – passenger side
0.4 @ passenger's head
0.3 @ passenger's waist
8.0 @ 15 cm from antenna
PCM Hawk
(100 W 4.78 GHz)
Rear of van driver's side
not detected inside van
17 @ 15 cm from antenna
Source: Author's own measurements plus measurements supplied by the Radiation Section,
Department of Health and Community Services, Victoria.
Conclusion
A number of conclusions can be drawn from the previous discussions. These are:
•
there do not appear to be any serious health problems caused by exposure to
RF radiation at or below the recommended limits in the Australian Standard;
•
the RF exposure levels to which police and law enforcement personnel are
exposed are, in general, lower than the recommended limits in the Australian
Standard;
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•
vehicular antennas should be mounted as far as is practicable from the
occupants of the vehicle. Covert antennas should not be placed in the head
rests of vehicles; and
•
specific operational procedures may need to be introduced with the use and
maintenance of some equipment in order to ensure compliance with the
Australian Standard.
References
Garson, O.M., McRoberts, T.L., Campbell, L.J., Hocking, B. & Gordon, I. 1991, ’A
chromosonal study of workers with long-term exposure to radio frequency radiation’,
Medical Journal of Australia, no. 155, pp. 289–92.
Hocking, B. 1984, Neoplasms of the Blood, Occupational Health Services, Paper
No. 6, Telecom Australia.
Hocking, B. & Joyner, K.H. 1991, 'Health risk management of radio frequency
radiation', Journal of Occupational Health & Safety: Australia and New Zealand,
vol. 8, no. 1, pp. 21–30.
Hollows, F.C. & Douglas, J.B. 1984, 'Microwave cataract in radiolinemen and
controls', Lancet, no. 2, p. 406.
Joyner, K.H. 1989, 'Microwave cataract and litigation: a case study', Health
Physics, no. 57, pp. 545–9.
Joyner, K.H., Lubinas, V., Wood, M.P., Saribalas, J. & Adams, J.A. 1992, 'Radio
frequency radiation (rfr) exposures from mobile phones', Proceedings of the IRPA
(Intensification of Research in Priority Areas) 8th World Congress, Montreal,
May 17–21.
Standards Australia 1991, Australian Standard AS2772.1 Radio Frequency Radiation,
Part 1: Maximum Exposure Levels, 100 kHz–300 GHz, North Sydney.
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