United States
Environmental Protection
Agency
 Health Effects
 Research Laboratory
 Research Triangle Park NC 27711
Research and Development
 EPA/600/S1 -86/006 Dec. 1986
Project  Summary
Effects of 60-Hz  Fields  on
Human  Health   Parameters

Mary R. Cook, Carl M. Maresh, and Harvey D. Cohen
  Research on the effects of exposure
to 60-Hz electric and magnetic fields
has provided contradictory evidence for
both increases and decreases in physio-
logical and metabolic functioning, and
specific results have often been difficult
to replicate. If biological responses to
powerline fields occur, they are un-
doubtedly subtle, and research strate-
gies  must be  specifically  designed to
enhance and clarify subtle effects.
  The study reported here used quanti-
tative exercise testing techniques to
evaluate whether increases in
metabolism,  caused by moderate
steady-state exercise prior to exposure
to real or sham fields, would clarify po-
tential field effects.
  This research showed that physical
recovery processes following moderate
steady-state exercise were the same in
real and sham fields. Of the variables
examined, only heart rate (cardiac in-
terbeat interval) was altered by 2 hr of
field exposure. A small, statistically sig-
nificant decrease in heart rate (3 beats/
min) was found when subjects were ex-
posed to the  real field after sitting
quietly prior to  exposure. This repli-
cates our earlier research, in which
heart  rate showed a similar decrease
after a total of 6 hr of field exposure.
The results suggest that future studies
should examine a broader range of the
continuum of human arousal and phys-
iological activation.
  This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park, NC,
to announce key findings of the re-
search project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
  Public concern has  been expressed
about possible health risks arising from
exposure to the electric and magnetic
fields generated by overhead power
transmission lines.  Previous  research
results have  often been contradictory
and difficult to replicate, suggesting
that field effects, if real, are subtle. Fur-
thermore, the literature suggests that
60-Hz fields might interact with neural
mechanisms important in the control of
levels of arousal. Research strategies.
specifically designed to elucidate subtle
effects are needed, and such strategies
should be used to directly investigate
the effects of field exposure  over the
continuum of human arousal.
  Quantitative  exercise testing tech-
niques have been quite helpful in im-
proving the understanding of mecha-
nisms associated with adaptation to
other  environmental conditions.  Con-
trolled exercise can be used  to  raise
physiological and metabolic function to
a higher level; at this higher level, sub-
tle changes in function may be more ap-
parent and therefore more easily mea-
sured. This research was based on the
idea that exercise testing methods
might be particularly promising in re-
search on 60-Hz field effects,  since re-
sults of previous studies on the effects
of field exposure have provided support
for both increases  and  decreases in
physiological functioning, as well as for
a dampening or shifting of normal circa-
dian variations.
  The research reported here had two
objectives: to evaluate the efficacy of
the approach by determining the feasi-
bility of combining  exercise and field
exposure techniques; and to  evaluate
whether increases in metabolism.

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caused by moderate steady-state exer-
cise prior to exposure to real or sham
fields, would clarify potential  field  ef-
fects.

Procedures

Experimental Design
  Each of eleven subjects participated
in a maximal exercise test, one familiar-
ization session, and four experimental
sessions. During the four experimental
sessions, which were held at weekly in-
tervals, four conditions were presented
in counterbalanced order: (1) exercise
on a bicycle ergometer at 50% of VO2
max for 45 min, followed by exposure to
sham  fields for 2 hr;  (2) exercise fol-
lowed by exposure to  real fields (9 kV/
m, 16 A/m) for 2 hr; (3) sitting quietly for
45 min, followed by exposure to sham
fields for 2 hr; and (4) sitting quietly fol-
lowed by exposure to real fields. All four
sessions were conducted under double-
blind conditions.
  Measure of cardiac activity, rectal
temperature, and biochemistry were
obtained at the end  of a 30-min equili-
bration period and  during the 45-min
pre-exposure period (exercise or sitting
quietly). Ratings of  perceived  exertion
also were collected  at 2-min intervals
during exercise. All measures except
rectal  temperature and perceived exer-
tion were obtained during recovery in
the real and sham fields. In addition,
continuous dosimetry measures were
taken  throughout exposure. At the end
of each session, both the experimenter
and the subject judged whether the real
or sham fields had been presented.

Exposure Facility and Double-
Blind Control System
  The exposure room  is positioned  in-
side a parallel plate system. A set of ca-
pacitively coupled, copper gradient
rings is located behind the walls to in-
crease field uniformity. The magnetic
field is generated by six Helmholtz coils,
surrounding the room  in both the verti-
cal  and  horizontal axes. Dedicated
equipment is used to maintain ambient
temperature and  relative humidity at
controlled levels, and the exposure area
is continuously monitored from two ad-
jacent control  rooms via closed-circuit
television and audio intercommunica-
tion equipment. Uniform electric and
magnetic fields can be generated in the
subject test area (0-16 kV/m, ± 5.6%; 0-
32 A/m, ± 4.8%). The vertical axis of the
magnetic field is in phase with the elec-
tric field, and the  horizontal axis is
phase shifted 90° with the electric field.
Additional equipment provides continu-
ous monitoring of electric and magnetic
field status, and individual short circuit
current  (Isc) throughout the exposure
period. During exposure periods in this
study the E field was set at 9 kV/m and
the magnetic field components set at 16
A/m.
  The double-blind  experimental con-
trol system allows presentation of real
and sham fields without either the sub-
ject or the experimenters being  aware
of which field condition is in effect at
any given time. Experimenters are kept
unaware of  exposure conditions
through a system of hardware and soft-
ware interlocks under the control of a
master computer program. The inter-
locks blank, mask, or disguise all field-
related cues in the control room equip-
ment.
  Our previous research indicated that
subjects could often perceive the fields
when they raised their hands in the air.
The double-blind system was designed
to counteract this major perceptual cue.
It uses the continuous  Isc monitoring
circuit to detect arm and hand move-
ment. Whenever continuous Isc ex-
ceeds an individually set reference
value, the strength of the electric field is
immediately decreased  by 75% for 30
sec,  and then  gradually returns to the
original 9 kV/m level. When the original
level is attained, the Isc comparison is
again made. If the hands are still raised,
field strength again  decreases; if Isc is
below the  reference value, field
strength continues to be maintained at
9 kV/m. Once an experimental session is
started,  operation of the double-blind
system is completely automatic.

Subjects
  Twelve men between 21 and 29 years
of age volunteered to participate in the
study, but only 11 subjects completed
all of the experimental sessions. All
were in good health  and had not partic-
ipated during the past year in a formal
aerobic conditioning program. Each
subject's daily activity pattern remained
consistent throughout the duration of
the study. After a complete and accurate
verbal description of the procedures,
risks, and benefits associated with the
study, each subject provided written in-
formed consent. Subjects were paid for
their participation.

Maximal Exercise Test
  In  addition to measuring each sub-
ject's aerobic power, the maximal exer-
cise test was designed to determine the
workload and heart rate that  most
closely corresponded with 50% of the
VO2 max.  Metabolic measurements
were assessed using a breath-by-breath
system.  The  subject wore  a  Hans-
Rudolph respiratory  mask (Hans
Rudolph, Incorporated) connected to a
Medical Graphics Wave-Form analyzer
(Medical Graphics Corporation); 02 and
C02 percentages were determined
using a Perkin-Elmer MGA 1100 mass
spectrometer.
  The subject cycled continuously on a
bicycle ergometer (Monark A.B.) at 60
rpm beginning with a 2-min workload of
0 kgm-min~1  followed by incremental
increases of 180 kgnvmin"1 every 3 min
until volitional exhaustion. To ascertain
that V02 max  had been  attained, each
subject was required  to meet at least
three of the following criteria: (1) no fur-
ther increase in oxygen uptake, despite
an increase in workload  (plateau crite-
rion); (2)  attainment of the age-
predicted maximal heart  rate; (3) a res-
piratory  exchange ratio (VC02/VO2)
greater than 1.10; and (4) a blood lactic
acid value of at least 8 mM-L~1 at 4 min
after exercise.

Experimental Sessions
  When a subject arrived at the labora-
tory, he changed into a  sweatsuit and
cotton socks. Electrodes for recording
heart  rate were attached, a rectal tem-
perature probe inserted, and a 20-gauge
cannula maintained patent with a hep-
arin lock inserted into a forearm vein.
After  a 30-min equilibration period, a
blood sample was drawn; the standard-
ized 45-min exercise/no-exercise period
then  began.  Under the no-excercise
condition, the  subject sat quietly read-
ing for the remainder of the period.
Under exercise conditions, the subject
cycled continuously (60 rpm) at appro-
priately adjusted workload  settings to
maintain the desired 50% of his previ-
ously determined V"O2 max. Heart rate
and core temperature were monitored,
and differentiated ratings of perceived
exertion were  recorded every 5 min. A
3-mL  blood sample was  drawn via the
cannula after  30 min of exercise for
measurement of lactic acid. Prior to con-
clusion  of the exercise test, another
blood sample was drawn for measure-
ment  of  all blood variables.  Identical
physiological  and  biochemical  meas-
ures  were obtained under the no-
exercise condition, except that the 30-
min lactate sample was not required.
  After the exercise period, the subject

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immediately entered the exposure facil-
ity. The rectal  probe and the subject's
shoes were removed, the subject put
the sweatshirt  back on, and the electric
field dosimetry "ground" was attached
to both ankles. This transition required
approximately 2 min. The real or sham
field was then activated by initiating the
computer  program. Cardiac  measures
were obtained continuously during the
exposure  period. Blood pressure and
blood samples for all blood variables
were obtained  at 10, 30, 60, 90, and 120
min after exercise. Approximately 2 min
of field deactivation was required each
time blood pressure readings and blood
samples were  obtained.

Results
  The first goal  of  statistical analysis
was to verify that the conditions speci-
fied in the experimental design were
met. No difference  in temperature or
humidity was  found between real and
sham exposure days. Subjects were un-
able to distinguish  between real and
sham conditions at better than chance
levels. All subjects met criteria for max-
imal exercise tests, and increased
metabolic  steady-state  was associated
with the 45-min exercise regimen.

Analysis of  Experimental
Variables
  Each dependent measure was sub-
mitted to three analyses. The first ad-
dressed the question of whether exer-
cise, as compared  to  sitting quietly,
altered the measure significantly. The
other two  analyses examined exercise
and no-exercise  conditions separately
to determine whether exposure to 60-Hz
fields had a significant effect. This strat-
egy was chosen since a major hypothe-
sis was that any field effects observed
would show higher  levels of statistical
significance after exercise. Data at 10,
30, 60, 90,  and  120 min from the end of
the exercise or resting period were used
for these analyses. An effect was
considered to be statistically significant
if  probability was .05 or less.  The
Greenhouse-Geisser correction  was
used to adjust for inflated degrees of
freedom due to repeated measures.
  Although exercise produced  the ex-
pected changes in the physiological and
biochemical measures, the variables
were not different under real and sham
field conditions subsequent to exercise.
However, when subjects rested quietly
prior to exposure, heart rate was slower
during  exposure  to the real fields than
during  exposure  to sham fields. Com-
parison between heart rate at the end of
the first 10 min of exposure and after
120 min of exposure indicated that, on
real field  exposure days, subjects
showed a significant decrease in heart
rate, while on sham exposure  days no
change was  found.  This  decrease in
heart rate associated with exposure to
the real fields occurred for 9 of the  11
subjects; the magnitude of the change
was correlated with  total  exposure to
the electric field as measured with short
circuit current (r = .49, df 9, p < .10). No
other differences in response between
real and sham field exposure were
found.

Conclusions and
Recommendations
  The feasibility of the methods and
procedures used was clearly estab-
lished. Exercise at 50% of maximal oxy-
gen uptake  produced the expected
changes in plasma volume and in hor-
mone, electrolyte, and lactic acid levels.
When subjects were subsequently ex-
posed to real and sham fields, the
double-blind  control procedures used
were  effective in preventing the sub-
jects from distinguishing between the
two conditions at better than chance
levels. If subjects sat quietly instead of
exercising during the preexposure pe-
riod, heart rate significantly decreased
during subsequent exposure to the real
fields. This phenomenon was also ob-
served in our  previous study of field ex-
posure  effects.  However, the use  of
moderate, steady-state exercise prior to
exposure did not serve to clarify field
effects.  The recovery process was the
same under real versus sham exposure
conditions.
  These results suggest  that future
work should focus on evaluation of the
effects of 60-Hz fields on the entire proc-
ess of exercise-induced activation and
recovery (pre-exercise, exercise, and re-
covery). Ideally, such studies  should:
(1) contrast exercise results with results
obtained after periods of very low phys-
iological arousal; (2) vary the duration
of exposure to fields  before exercise;
and (3) examine the effects of different
intensities of exercise in the fields.

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    MaryR. Cook, Carl M. Maresh, and Harvey D. Cohen are with Midwest Research
      Institute, Kansas City. MO 64110.
    Carl F. Blackman is the EPA Project Officer (see below).
    The complete report, entitled "Effects  of  60-Hz Fields on  Human  Health
      Parameters," (Order No. PB 86-231 297/AS; Cost: $ 11.95. subject to change)
      will be available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA 22161
           Telephone: 703-487-4650
    The EPA Project Officer can be contacted at:
           Health Effects Research Laboratory
           U.S. Environmental Protection Agency
           Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for EnviroRrffSntal Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S1-86/006


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