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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,

S.M. Harvey,

P. Jutras,

D. Goulet,

* and R. Mandeville

PS M Consulting, Bouch ervill e, Qu e

bec , Canada

SAIC Canada, Brampton , Ontario, Canada

Tr a n s E

nerg ie, Mo ntre

al, Que

bec , Canada

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

tage, Montreal, P.Q.; Canada H2L 4M8.

E-mail: goulet.daniel@hydro.qc.ca

Received 1 March 1999; Final revision received 10 November

1999.

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



* The variation in long-term stability of MF in each

exposure unit was  1% and that of temperature

was  0.1



* 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

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

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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