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A magnetic field exposure facility for evaluation of animal carcinogenicity Bioelectromagnetics 21:432^438 (2000) AMagnetic Field Exposure Facility for Evaluation of Animal Carcinogenicity P.S. Maruvada,1 S.M. Harvey,2 P. Jutras,1 D. Goulet,3* and R. Mandeville4 1PSMConsulting, Boucherville, Quëbec, Canada 2SAIC Canada, Brampton, Ontario, Canada 3TransËnergie, Montrëal, Quëbec, Canada 4Biophage Inc., Montrëal, Quëbec, Canada Several animal studies have been carried out at the Institu
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Bioelectromagnetics 21:432 ^438 (2000)
A M agnetic Fi e ld Exposure Faci lity for
Eval uatio n of An i m al Carcinoge n icity
P.S. Maruvada,
1
S.M. Harvey,
2
P. Jutras,
1
D. Goulet,
3
* and R. Mandeville
4
1
PS M Consulting, Bouch ervill e, Qu e
¨
bec , Canada
2
SAIC Canada, Brampton , Ontario, Canada
3
Tr a n s E
¨
nerg ie, Mo ntre
¨
al, Que
¨
bec , Canada
4
B iophage I nc ., Montre
¨
al, Que
¨
bec , Canada
Several animal studies have been carried out at the Institut Armand Frappier (IAF) to determine
whether chronic exposure to 60 Hz linearly polarized sinusoidal magnetic fields might increase the
risk of cancer development of female Fisher rats. The magnetic field exposure facility was
developed to meet the requirements of the study protocol for chronic exposure of large number of
animals to field intensities of sham < 0.2 mT, 2 mT, 20 mT, 200 mT, and 2000 mT. At each exposure
level, including sham, the animals are distributed in a group of four exposure units. Each exposure
unit contains two exposure volumes having uniform distribution of magnetic fields for the animals,
while the magnetic field external to the unit falls off rapidly due to the ``figure-eight'' coil
topography used. A program of ``shake down'' tests, followed by verification and calibration of the
exposure facility, was carried out prior to starting the animal experiments. Continuous monitoring
of the magnetic field and other environmental parameters was an important part in the overall
quality assurance program adopted. Bioelectromagnetics 21:432±438, 2000.
ß 2000 Wiley-Liss, Inc.
Key words: laboratory study; animal carcinogenicity; magnetic fields; 60 Hz
INTRODUCTION
Following Wertheimer and Leeper [1979], a
number of epidemiological studies have been carried
out to determine whether exposure to power±fre-
quency magnetic ®elds (MFs) is associated with the
occurrence of certain types of cancer, particularly
leukemia, brain tumors, and breast cancer in men and
women. The results obtained so far show, however, that
the indices supporting any hypothesis that exposure
to MFs may cause cancer are very weak. Inherent
dif®culties in the methodology, such as dosimetry for
exposure assessment, absence of dose±response rela-
tionship and the small number of cases studied, limit
the interpretation of results obtained from epidemio-
logical studies. In order to obtain de®nitive informa-
tion on cause-and-effect relationships, there is a need
for carefully designed animal studies that would offer
the possibility of exposing large number of inbred
animals to graded intensities of power±frequency MFs
in a carefully controlled environment.
One of the ®rst such studies has been carried
out at the Institut Armand-Frappier (IAF), Montreal,
Quebec, with the objective of determining whether
chronic exposure to 60 Hz linearly polarized sinusoidal
MFs of different intensities might increase the risk of
leukemia and solid tumor development in female F344
rats [Mandeville et al., 1993, 1997, 1999; Tremblay,
1996]. The study design required exposure of ®ve
groups of 50 rats each for 20 h/day to MFs at intensities
of < 0.2 (sham controls), 2, 20, 200, and 2000 mTovera
period of 104 weeks. The study protocol also required
careful control of MF intensities and other environ-
mental parameters as well as double-blind operation of
the exposure facility. The design, operation, veri®ca-
tion, monitoring, and maintenance of a high quality
exposure system developed for this study is described
in this paper.
MATERIALS AND METHODS
Tec hnical Specifications for the
Exposure Facility
In order to meet the requirements of the study
design and the experimental protocol, technical
ß 2000 Wiley-Liss,Inc.
ÐÐÐÐÐÐ
*Correspondence to: Dr. Daniel Goulet, Direction Expertise et
Support technique de transport; TRANSENERGIE, 800 boul. De
Maisonneuve est, 21e e
Â
tage, Montreal, P.Q.; Canada H2L 4M8.
E-mail: goulet.daniel@hydro.qc.ca
Received 1 March 1999; Final revision received 10 November
1999.
![](https://csdnimg.cn/release/download_crawler_static/19899135/bg2.jpg)
speci®cations have been developed for the design and
construction of the MF exposure facility. The 50
animals at each of the ®ve levels of MF, including
sham, have been distributed into four exposure units,
which constituted an exposure facility comprising of
twenty identical exposure units. The technical speci-
®cations prepared for the exposure facility are:
* The ®ve MF levels to which the animals were
exposed were sham (< 0.2 mT), 2 mT, 20 mT, 200 mT
and 2000 mT;
* The MF generated inside each exposure unit by the
®eld coils were distributed uniformly in the volume
occupied by the animals;
* The external MF generated by each exposure unit
had negligible in¯uence on the MF inside any
neighboring exposure unit;
* The exposure units were arranged inside the
exposure room in ®ve rows of four units each, each
row corresponding to one MF level. Each row of
exposure units had negligible in¯uence on any of
the adjacent rows;
* The temperature in all exposure units were equal
with the difference being 1
C;
* The variation in long-term stability of MF in each
exposure unit was 1% and that of temperature
was 0.1
C;
* The ®ve MF levels, including sham, were inter-
changeable among the ®ve rows of exposure units in
a ``blind'' manner;
* The MF was to be ramped up and down at the start
and end, respectively, of each exposure period, to
prevent undesired transient responses;
* Any artifacts, such as sound, vibration, electric ®eld,
associated with MF generation were adequately
controlled.
Design and Construction of the
Exposure Facility
Exposure and control rooms The MF exposure
facility is located in building 25 of IAF, which was
dedicated for use only for this study. In this building,
an ``exposure room,'' having a ¯oor area of about
154 m
2
was used for long-term exposure of animals to
the ®ve MF levels and a small room adjacent to it was
used as a ``control room.'' The control room was fully
separated from the exposure room, except for a glass
viewing window, which was covered with a blind
during the dark periods of animal exposure. Access to
both these rooms was restricted to authorized person-
nel only. The current in the coils of the different rows
of exposure units was controlled and monitored from a
panel located in the control room.
Animal cages Each exposure unit contained eight
animal cages, four placed at the top and four at the
bottom exposure volume, and each cage accommo-
dated two adult rats. The cages were located in the
space at the center of both the top and bottom sets of
coils, a design to generate uniformly distributed MF
level in each cage. Thus each exposure unit can
accommodate 16 rats and a maximum of 64 animals
can be exposed to each of the ®ve MF levels. Each
cage, having dimensions of 28.5 28.5 18 cm and
made of polycarbonate material, is provided with ¯at
stainless steel cover top that holds a 500 mL glass
bottle ®tted with a No. 6
1
2
rubber stopper with a glass
sipper and a suspended ceramic feeder. The cage cover
is provided with a small Te¯on tubing so as to interrupt
the full vertical loop in the stainless steel cover. The
four cages in each exposure volume are placed on a
polycarbonate tray (59 59 cm).
Field coils Circular or square Helmholtz coils have
generally been used [Misakian, 1984] to obtain an
exposure volume with a desired degree of magnetic
®eld uniformity. Substantial improvements in the
uniform-®eld exposure volume may be achieved by
using three-, four-, and ®ve-coil systems, in which the
number of turns in each coil and the spacings between
the turns are chosen to maximize the exposure volume
[Garrett et al., 1971; Kaminishi et al., 1981; Grisenti
et al., 1981; Merritt et al., 1983]. In studies of
biological effects of magnetic ®elds, it is often
necessary to have sham exposure units which are
similar to the actual exposure units and positioned
close to them, but which require negligible magnetic
®eld in the exposure volume. The twin objectives of
having a suf®ciently large uniform-®eld exposure
volume in the exposure unit while at the same time
minimizing the stray external ®elds produced by the
coils may be met by using nested coils [Purcell, 1989]
or other quadrupolar con®gurations. The ``®gure-
eight'' quadrupole coil con®guration has been used
in several recent studies [Harvey, 1988; Miller et al.,
1989; Wilson et al., 1994]. The dimensions, spacing,
and the number of turns of the ``®gure-eight'' coil
con®guration used in the present study have been
computer generated to optimize the ®eld uniformity
over the actual cage dimensions.
As described above, each exposure unit has two
exposure volumes, located at the top and the bottom of
the unit. Four rectangular ®eld coils, placed coaxially
and parallel to each other, produce the uniform MFs in
each exposure volume. Thus, a total of eight ®eld coils
are required for each exposure unit and they are all
connected in series, so that the same current ¯ows in
all the coils. Of the four coils used for an exposure
Animal Magnetic Field Exposure Facility 433
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