Embed Size (px)
Citation preview
SCIENTIFIC PAPER
No effects of power line frequency extremely low frequencyelectromagnetic field exposure on selected neurobehavior testsof workers inspecting transformers and distribution line stationsversus controls
Li Li • De-fu Xiong • Jia-wen Liu • Zi-xin Li •
Guang-cheng Zeng • Hua-liang Li
Received: 20 June 2013 / Accepted: 16 December 2013 / Published online: 31 December 2013
� Australasian College of Physical Scientists and Engineers in Medicine 2013
Abstract We aimed to evaluate the interference of 50 Hz
extremely low frequency electromagnetic field (ELF-EMF)
occupational exposure on the neurobehavior tests of
workers performing tour-inspection close to transformers
and distribution power lines. Occupational short-term
‘‘spot’’ measurements were carried out. 310 inspection
workers and 300 logistics staff were selected as exposure
and control. The neurobehavior tests were performed
through computer-based neurobehavior evaluation system,
including mental arithmetic, curve coincide, simple visual
reaction time, visual retention, auditory digit span and
pursuit aiming. In 500 kV areas electric field intensity at
71.98 % of total measured 590 spots were above 5 kV/m
(national occupational standard), while in 220 kV areas
electric field intensity at 15.69 % of total 701 spots were
above 5 kV/m. Magnetic field flux density at all the spots
was below 1,000 lT (ICNIRP occupational standard). The
neurobehavior score changes showed no statistical signifi-
cance. Results of neurobehavior tests among different age,
seniority groups showed no significant changes. Neurobe-
havior changes caused by daily repeated ELF-EMF expo-
sure were not observed in the current study.
Keywords Extremely low frequency electromagnetic
field (ELF-EMF) � Occupational exposure �Neurobehavior test
Introduction
In the past two decades, a great number of studies focused
on the effects of electromagnetic fields (EMFs) on human
physiology, for example, heart rate variability [1] and
cognitive performance [2, 3]. Although there was guid-
ances published by ICNIRP (2010) and IEEE (2002),
which are based on the avoidance of acute effects in the
central nervous system (CNS), there were still many
investigations that focused on the relationship between
extremely low frequency electromagnetic field (ELF-EMF)
exposure and variety of the interferences on neurobehavior.
Studies suggesting that magnetic field (MF) (50 Hz,
1,000 lT) exposure could have a subtle delayed but not
pathological effect on human behavior [4]. Another pre-
vious study recorded that 1 h MF (60 Hz, 1,800 lT)
exposure might modulate human involuntary motor control
without being detected in the cortical electrical activity [5].
A small negative delayed effect of a 50 Hz, 100 lT MF
exposure on memory recognition accuracy although no
effect in reaction time and accuracy in the visual dis-
crimination task were observed [3]. There was also study
presenting data that suggest detrimental effects of a 50 Hz,
28 lT MF on short-term memory and executive functions
[6]. Furthermore, a decreased performance in attention and
several working and secondary memory tasks under
exposure to a 50 Hz, 0.6 mT MF was found [7]. Addi-
tionally, subjects showed decreased accuracy in a choice
reaction task. For example, a previous study revealed a
small improvement in the accuracy of a visual duration
discrimination task under exposure to 50 Hz, 100 lT MF
[8]. The result of another study centering on reaction time
showed that ELF-MF had a relaxing effect on motor con-
trol and resulted in an attenuation of postural tremor
intensity [9]. Besides, the postural tremor of subjects were
L. Li (&) � J. Liu � G. Zeng � H. Li
Electric Power Research Institute of Guangdong Power Grid
Corporation, No. 8 Shuijungang Dongfengdong Road,
Guangzhou 510080, Guangdong, China
e-mail: [email protected]
D. Xiong � Z. Li
Guangdong Huianhengda Management Consulting Co., Ltd,
Guangzhou, China
123
Australas Phys Eng Sci Med (2014) 37:37–44
DOI 10.1007/s13246-013-0237-6
affected by MF (50 Hz, 1,000 lT) exposure, but the sen-
sitivity of individual subjects to this effect exerted differ-
entially [10]. Another issue on this topic is whether the
effects of ELF-EMF exposure on neurobehavior could be
persistent after the exposure ceased.
On the other hand, there were studies indicating that
ELF-EMF had no impact on neurobehavior performance.
In a study, no effects of 50 Hz, 400 lT MF exposure on
attention, working memory, integrate information ability
and simple reaction time were found [11]. Similar to that,
another study investigated the effects of 400 and 20 lT,
50 Hz MF on several tasks completed by subjects on
attention, working memory, cognitive flexibility, and time
perception also found no meaningful results [12]. There
was also a study showing decreased errors and non-affected
reaction time in a choice reaction task, but performances in
a simple reaction task, an attention task and a memory task
were not affected by exposure to a 60 Hz ELF-EMF [13].
The inconsistency of the findings and the failures of rep-
lication attempts could be attributed partially to the dif-
ferences of exposure conditions, such as frequency,
duration, flux density, measurements after or during the
exposure, individual sensitivity, etc. (see [2, 9, 10, 13] for a
review) Also, it had to be noted that interpretation of the
results was limited by the diversity of the neurobehavior
tests that were applied in the studies mentioned above.
At present, little is known about the biological mecha-
nisms underlying the suspected impact of ELF-EMF
exposure on neurobehavior abilities. There is some spec-
ulation that frontal and parietal cortex activity might be
affected by MF exposure, however, this hypothesis has
never been verified [14], although many researchers have
described redox-related cellular changes following ELF-
MF exposure [15, 16]. There are possible mechanisms that
ELF-EMF might influence the motor coordination, spatial
and short-term working memory by intervening synaptic
potentials of Purkinje cells, which form the main output of
the cerebellum, and pyramidal cells in the hippocampus
[13]. Researchers recently demonstrated that ELF-MF
exposure could cause significant changes in antioxidant
capacity, together with a reduced tolerance towards oxi-
dative challenges and DNA damage in newborn rats [17].
In vitro and in vivo results together might allow a rough
interpretation, but in order to develop strategies concerning
public health, studies on occupationally exposed popula-
tion are still in need.
So far as we know, the persistence of the effects of ELF-
EMF exposure is not clearly established. Therefore, in the
current study, we conducted a series of computer-based
neurobehavior tests in 310 regularly ELF-EMF exposed
subjects, compared with 300 control subjects. All of the
310 exposed and 300 control subjects finished the com-
puter-based tests in an ample room where the ELF-EMF
level could not be detected with the same measure device.
We aimed to examine whether there were effects and, if so,
which functions of the CNS might be affected and whether
the effects could be detectable after long-time repeated
ELF-EMF exposure, because the neurobehavior tests were
being regularly used to recognize sub-clinical symptoms of
CNS dysfunction that might be caused by ELF-EMF
exposure.
Materials and methods
Subjects
Subjects with CNS diseases like epilepsy (epilepsy family
history), cerebritis (cerebritis history), severe brain trauma
history, visual and auditory disturbance, upper limb dys-
kinesia were not qualified to be involved in the current
study. A total of 710 subjects with good state of health
were recruited and designated into exposure (n = 364) and
control (n = 346) group depending on whether there was
an occupational history of ELF-EMF exposure. The
research protocol was approved by the Institutional Review
Board (The Ethics Committees of Electric Power Research
Institute of Guangdong Power Grid Corporation, Guangz-
hou, China). Informed consent and Health Insurance Por-
tability and Accountability consent were obtained from
each subject. All the 25 investigators received standard and
unified training before the investigation started. All sub-
jects were required to complete a series of neurobehavior
tests (Table 1) unless they were not willing to, including
tests on mental arithmetic, visual retention, auditory digit
span and visual simple reaction time on the same laptops,
which mainly included memory recognition accuracy,
visual discrimination, short-term memory, cognitive per-
formance and executive functions. Six control and four
exposed workers were not willing to take the neurobe-
havior tests for unknown reasons. All the subjects (except
the six control and four exposed workers) were also
required to complete a questionnaire that were finished in
Table 1 Testing items of NES neurobehavioral capacity
Item (neurobehavioral capacity) Name
Intelligence Mental arithmetic
Learning and memory Visual retention
Perception and number-involved
memory capacity
Auditory digit span
Mental campaign and
hand-eye coordination
Visual simple
reaction time
Curve coincide
Pursuit aiming
38 Australas Phys Eng Sci Med (2014) 37:37–44
123
no \15 min, which included questions about age, sex,
nationality, smoking, alcohol, green tea drinking, medicine
intake, medical inspections like chest perspective, X-ray
based imagery and barium meal (in recent half year),
emotional shock or trauma like being victim of a violent
crime or losing a family member (in recent half year). After
each of the 700 subjects finished the questionnaire in
2 months, 610 of the total 700 questionnaires were selected
and were input with Epidata software (version 3.1). Other
90 subjects did not meet the inclusion criteria in part
because of incomplete data collection or because they had
past medical histories of mental diseases. 300 subjects
comprised 276 males and 24 females aged 23–50 years
(mean = 31.6 years) were finally selected as control. This
group included administrative staff and logistical personnel
who were not authorized to enter the 500 and 220 kV zone
during workday. The exposure group consisted 310 work-
ers who performed tour-inspection close to voltage trans-
formers and distribution power lines, including 284 males
and 26 females aged between 25 and 49 years
(mean = 30.5 years). All of the 310 exposed workers had
an occupational history of long-time ELF-EMF exposure
varying from 3 to 25 years. The inspectors worked in the
similar office environment with the control subjects while
the inspectors were not performing tour-inspection. Both
the inspectors and the control subjects exposed constantly
to ELF-EMF produced by computers and household
appliances and circuits. A pre-enrollment survey showed
no disease-related symptoms among control and exposure
subjects. None of the 610 subjects reported family history
or past medical history of mental and cardiovascular dis-
eases. All subjects denied having history of hepatitis, liver
or kidney failure.
ELF-MF measurement protocols
The 500 kV areas were grouped into three types depending
on the placement of equipments. Type A: The electrical
equipment was set outdoor, circuit breaker, switch, current
transformer (CT) and busbar potential transformer (PT)
were fixed independently in an open-plan. Type B: The
electrical equipment was set outdoor, circuit breaker,
switch, CT and PT were fixed assembly in combined
arrangement, called ‘‘Half GIS’’. Type C: The electrical
equipment was set in a room that was built with concrete,
with a gas insulation closed switch, called ‘‘GIS’’. 220 kV
areas were also grouped into type A: The electrical
equipment was set out door, circuit breaker, switch, CT and
PT were fixed independently in an open-plan. Type B: The
electrical equipment was set outdoor, with a gas insulation
closed switch, called out door ‘‘GIS’’. Type C: The elec-
trical equipment was set indoor, with a gas insulation
closed switch, called indoor ‘‘GIS’’.
Three-axis ELF-EF intensity and ELF-MF flux density
outdoor in the 500, 220 kV areas of voltage transformers
and distribution power lines respectively were measured
with PMM 8053A portable field meter with an EHP50
three-axial probe (PMM Construction Center for Elec-
tronic Radio Measurements, Cisano Sul Neva, Italy) at
spots located in the routes where workers regularly per-
form tour-inspections. The spots started 2 m away from
the enclosing wall and dotted in the route of tour-
inspection, which surround 500 or 220 kV areas respec-
tively, with 5 m apart from each other and 1.5 m high
from the ground. Besides, it is necessary to mention that
the investigated frequency in current study is 50 Hz.
Computer-based neurobehavior tests
Neurobehavior tests were performed on 25 specified lap-
tops through computer neurobehavioral evaluation system
(NES) software, in a quiet room with soft light. All of the
310 exposed and 300 control subjects finished the com-
puter-based tests in a large room where the ELF-EMF was
below the level of detection using the survey meter
described in section ‘‘ELF-MF measurement protocols’’.
All the qualified subjects were told not to take alcohol, nor
did take any depressant or stimulant medicine 12 h before
the tests. Items including mental arithmetic, curve coin-
cide, simple visual reaction time, visual retention, auditory
digit span and pursuit aiming were set in NES software for
the tests of subjects (Table 1). A standard procedure of the
tests and the algorithms of the tests score or index in the
NES software were based on the WHO neurobehavioral
core test battery (NCTB) [18].
Statistical analysis
The group average of neurobehavior tests score and/or
match capability index were calculated and presented in
form of mean ± standard deviation (SD), and range for
95 % confidence interval was included. Neurobehavioral
test score and index between control and exposure were
compared by student t test, with green tea drinking and
alcohol consumption being treated as covariant through
covariance analysis. The total group averages and aver-
ages in different age (\30, 30–40, 40 years) or seniority
groups (control, \5, [5 year) of neurobehavior evalua-
tion score and index were compared using one-way
ANOVA to determine if any statistical significance
existed. All P values \0.05 were considered as statisti-
cally significant. All the statistical analysis was per-
formed using SPSS 11.0 software (SPSS Inc., Chicago,
USA).
Australas Phys Eng Sci Med (2014) 37:37–44 39
123
Results
Analysis of neurobehavior influencing factors
between control and exposure group
Both the control and exposure group were exposed con-
stantly to ELF-EMF produced by household appliances and
circuits. The levels of ELF-MF produced by household
appliances varied tremendously and could reach
1,500–2,000 lT, like electric shaver or hairdryer [19, 20].
In the current study, the total levels of ELF-EMF produced
by household appliances that both the control and exposure
group were exposed to were not assumed statistically
different.
Each subject was required to complete a questionnaire,
in order to investigate the equilibrium of neurobehavior
influencing factors between control and exposure group.
The equilibrium of the items between control and exposure
group were analyzed with v2 test. All the distribution of the
influencing factors between control and exposure group
were not found significantly different, except alcohol and
green tea (P \ 0.05). The distribution proportion of sub-
jects who were accustomed to alcohol and green tea
drinking were in disequilibrium between control and
exposure, which should be taken into account while doing
further statistical analysis of neurobehavior score and index
(Table 2).
The ELF-EMF level of 500 and 220 kV transformers
and distribution lines
The ELF-EMF level at the spots dotted in the route of tour-
inspections nearby 500 and 220 kV transformers and dis-
tribution lines were measured respectively. Both magnetic
and electric filed intensity at type A, B and C 500 kV areas
were different (Table 3). The ELF-EF intensity of more
than 50 % of the spots measured was above 5 kV/m at type
A, B 500 kV areas, which is the national ELF-EF exposure
limit of China. However the ELF-EF intensity was not
found higher than 5 kV/m at the spots in type C 500 kV
areas. The ELF-EF intensity at 110 spots in type A 220 kV
areas was above 5 kV/m (Table 4). It was reported by the
workers performing tour-inspection that the duration time
spent at particular locations range from 2 to 15 min.
Table 2 Equilibrium analysis of neurobehavioral influencing factors
Items Control Exposure P
Sex
Male 276 284 0.906
Female 24 26
Nationality
Han 296 307 0.704
Other 4 3
Smoking
Smoker 84 66 0.054
Non smoker 216 244
Alcohol
Never 26 52 0.000
Occasionally 244 249
Frequently 28 9
Not clear 2 0
Green tea
Never 5 18 0.000
Occasionally 158 199
Frequently 134 90
Not clear 3 3
Medicine (within 2 weeks)
No 294 301 0.471
Ever 6 9
X-ray (within half year)
No 276 281 0.553
Ever 24 29
Computerized tomography (within half year)
No 292 297 0.301
Ever 8 13
Barium meal (within half year)
No 299 309 1.0
Ever 1 1
Mental stress (within half year)
No 283 295 0.718
Ever 17 15
Body stress (within half year)
No 295 306 0.748
Ever 5 4
Table 3 The ELF-EMF level of the spots dotted at 500 kV
Type A B C
Total measured spots number 360 180 50
ELF-EF intensity
Maximum (kV/m) 14.00 11.91 4.0 9 10-4
Minimum (kV/m) 0.651 1.648 9.0 9 10-5
Median(kV/m) 7.310 6.517 1.4 9 10-4
C5 kV/m spots number 296 133 0
ELF-MF intensity
Maximum (lT) 30.19 19.57 32.02
Minimum (lT) 0.620 0.791 1.426
Median (lT)) 17.83 11.99 16.52
C1,000 lT spots number 0 0 0
Duration time ranges at particular
locations (min)
2–10 2–10 2–15
40 Australas Phys Eng Sci Med (2014) 37:37–44
123
Neurobehavior evaluation score and index were
not different between control and exposure group
The neurobehavior capacity tests including mental arith-
metic, curve coincide, simple visual reaction time, visual
retention, auditory digit span and pursuit aiming test, were
carried out for each individual. The items of neurobehavior
tests were treated as dependent, ELF-EMF exposure as
independent. No significant differences were found
between control and exposure group, even after green tea
and alcohol were treated as covariant through covariance
analysis (Table 5).
Neurobehavior evaluation score and index were
not significantly different among different age
and seniority groups
560 male volunteers were grouped according to the age
(\30, 30–40, 40 years) and length of service (control, \5,
[5 year). 50 female volunteers were parted into control
and exposure group. Neurobehavior evaluation were car-
ried out for each individual and compared in different
groups mentioned above with one-way ANOVA. No sta-
tistical differences in neurobehavior evaluation score and
index were found among different age and seniority groups
(Table 6).
Discussion
Among the environmental risk factors that affect human
health, ELF-EMF might play an role in neurological dis-
eases and neurobehavior performance in adults [21–23].
Studies showed that ELF-EMF exposure could influence
the motor control [9], cognitive performance [11] and
cognitive function [12] in humans. Therefore, we assumed
that abnormal neurobehavior tests results were signs of the
alteration of CNS function. However, there are also studies
indicating that ELF-EMF have no impact on neurobehavior
activities [24, 25]. In the current study, we measured the
ELF-EMF exposure level of workers performing tour-
inspection close to 500 and 220 kV transformers and dis-
tribution power lines, and conducted a series of tests on the
computer system to examine whether there were effects
and, if so, which neurobehavior activity of the CNS might
be affected.
Table 4 The ELF-EMF level of the spots dotted at 220 kV
Type A B C
Total measured spots number 605 48 48
ELF-EF intensity
Maximum (kV/m) 9.52 3.623 6.0 9 10-4
Minimum (kV/m) 0.068 0.053 8.0 9 10-5
Median(kV/m) 6.862 1.331 2.659
C5 kV/m spots number 110 0 0
ELF-MF intensity
Maximum (lT) 60.11 44.54 16.23
Minimum (lT) 0.509 0.396 1.337
Median (lT)) 36.680 20.371 6.833
C1,000 lT spots number 0 0 0
Duration time ranges at particular
locations (min)
2–10 2–10 2–15
Table 5 Neurobehavioral tests score and index between control and
exposure
Item Statistical
index
Control Exposure
Total mental arithmetic Number 300 310
Average 26.90 27.27
SD 7.37 7.35
P 0.55
Accurate mental arithmetic Number 300 310
Average 25.92 26.02
SD 7.56 7.45
P 0.79
Visual reaction Number 300 310
Average 7.35 7.45
SD 1.92 1.78
P 0.57
Auditory digit span Number 300 310
Average 17.36 17.08
SD 6.03 6.07
P 0.35
Simple visual reaction time Number 300 310
Average 0.421 0.414
SD 0.099 0.092
P 0.27
Curve coincide Number 300 310
Average 370.09 365.37
SD 99.67 111.58
P 0.32
Total pursuit aiming number Number 300 310
Average 109.87 111.15
SD 25.17 26.59
P 0.67
Accurate pursuit aiming number Number 300 310
Average 99.51 100.47
SD 20.89 21.62
P 066
Each P value was obtained while tea and alcohol were treated as
covariant through covariance analysis
Australas Phys Eng Sci Med (2014) 37:37–44 41
123
The exposure level in the current study is higher than
that measured in other industries in China, like automotive
industry [26]. Besides, the ELF-MF level in the current
study is also higher than that measured in residential
apartments close to transformers or distribution power lines
in other countries, like Hungary [27], Finland [28] and
Israel [29]. The exposure group in the current study is
exposed to relative higher levels of ELF-EMF than the
ELF-EMF exposure groups reported in the researches
mentioned above. However, uncertainty evaluation needs
to be considered in the measurement of ELF-EMF [30],
which would increase the comparability of different mea-
surement results.
A recent study showed that ELF-EMF might have
effects on the nervous, cardiovascular, liver and
hematology system of workers in automotive industry [26].
However, in current study, the items of neurobehavior tests
were treated as dependent, ELF-EMF exposure as inde-
pendent, no significant differences were found between
control and exposure group, even after green tea and
alcohol were treated as covariant through covariance ana-
lysis. Further analysis was carried out in different age,
seniority groups, but no statistical significant results were
found either. Obviously, our results do not seem to support
our assumption, but there are always inconsistencies
among results of in vivo, in vitro and epidemic studies. The
inconsistencies might be attributed mainly to the differ-
ences of the demographic characteristics of the study
subjects and experimental conditions, etc. [9, 10, 13]. On
the other hand, in a recent research, a considerable nocebo
Table 6 Neurobehavioral evaluation score and index among different age or seniority group
Group Accurate mental arithmetic Visual retention Auditory digit span Simple visual reaction time
Sex Age Seniority Number Average P Number Average P Number Average P Number Average P
Male \30 Control 141 28.13 141 7.78 141 18.91 141 0.412
\5 years 123 27.97 0.98 123 7.80 1.00 123 18.41 0.70 123 0.394 0.22
C5 years 28 26.07 0.31 28 8.07 0.60 28 19.18 0.96 28 0.428 0.65
30–40 Control 99 25.31 99 7.07 99 16.91 99 0.429
\5 years 25 26.04 0.87 25 7.08 1.00 25 17.84 0.70 25 0.432 0.99
C5 years 78 25.03 0.95 78 7.26 0.77 78 17.05 0.98 78 0.419 0.77
C40 Control 36 19.72 36 6.50 36 11.94 36 0.421
\5 years 7 19.71 1.00 7 6.57 1.00 7 8.29 0.21 7 0.445 0.75
C5 years 23 22.87 0.15 23 6.26 0.90 23 10.22 0.42 23 0.445 0.50
Total Control 276 26.03 276 7.36 276 17.28 276 0.419
\5 years 155 27.28 0.17 155 7.63 0.27 155 17.86 0.54 155 0.403 0.17
C5 years 129 24.87 0.25 129 7.26 0.83 129 16.29 0.22 129 0.425 0.79
Female Control 26 24.27 26 7.38 26 16.42 26 0.422
Exposure 24 24.54 0.91 24 7.25 0.80 24 18.04 0.36 24 0.440 0.32
Group Accurate pursuit aiming Curve coincide
Sex Age Seniority Number Average P Number Average P
Male \30 Control 141 105.08 141 374.08
\5 years 123 105.41 0.99 123 378.28 0.93
C5 years 28 106.07 0.96 28 343.11 0.25
30–40 Control 99 97.88 99 373.31
\5 years 25 95.24 0.80 25 382.76 0.89
C5 years 78 98.64 0.96 78 369.09 0.95
C40 Control 36 83.44 36 326.78
\5 years 7 87.29 0.87 7 368.14 0.66
C5 years 23 90.70 0.33 23 316.70 0.94
Total Control 276 99.67 276 367.63
\5 years 155 102.95 0.21 155 378.55 0.50
C5 years 129 98.84 0.91 129 354.11 0.39
Female Control 26 94.00 26 348.77
Exposure 24 98.17 0.47 24 400.96 0.09
42 Australas Phys Eng Sci Med (2014) 37:37–44
123
effect in symptoms related to 50 Hz EMF exposure was
reported, because idiopathic environmental intolerance to
EMF seemed to be formed through a vicious circle of
psychosocial factors, such as enhanced perception of risk
and expectations, self-monitoring, somatization and
somatosensory amplification and misattribution [25]. On
this basis, previous studies that reported ELF-EMF expo-
sure influenced the neurobehavior activities might not take
the nocebo effect into account when the conclusions were
made.
Besides, despite all that mentioned above, there are
possibilities that ELF-EMF exposure might induce or
promote effects (probably damages) on CNS. In the last
few years, both in vitro and in vivo studies on the health
effects of ELF-EMF exposure described redox-related
changes in CNS following ELF-EMF exposure [16, 31]. In
fact, abnormal neurobehavior might emerge after but not
before the alteration of CNS function, which means that we
should have chosen biomarkers that emerge in earlier state
of the alteration of CNS function. Such as nerve growth
factor (NGF) which is widely recognized to play a crucial
role in the process of free radicals scavenging and neuronal
systems protection [32]. Therefore, more reliable and ear-
lier biomarkers would be applied in following studies. On
the other side, the effects of ELF-EMF exposure on CNS
could only be detected during the exposure, and the effects
might be disappeared as soon as the exposures stops [9,
33]. This indicated that the effects of ELF-EMF on humans
CNS function, if any, exerted in a on and off way, but the
cumulative effects of long-term intermittent ELF-EMF
exposure were not observed in the current study. That
means ELF-EMF might have transient effects without
interfering with the CNS in a way measured here. Nerve
cells are spontaneously active in awake animals, soma and
dendrite membrane potentials continually fluctuate. So
there is a possibility that thresholds for impulse initiation
by externally ELF-EMF would be lowered than those
necessary for the direct stimulation of peripheral nerves
[34], however, the overall effect could be either excitatory
or inhibitory, depending on the functional and brain tissue
properties of the neuron(s) involved [13, 14, 35].
In all, despite the shortcomings mentioned in the current
study, it seemed that long-term intermittent ELF-EMF
exposure do not appear to disrupt normal neurobehavior
like learning and memory capacity, perception and num-
ber-involved memory capacity, mental campaign and hand-
eye coordination. The acute effects of ELF-EMF exposure
were not explored and discussed in the current study, and
the possible cumulative effects of ELF-EMF exposure on
the CNS functions mentioned above were not observed in
the current study. In the future, researches on this issue
must include subjects that exposed to higher level of ELF-
EMF, in order to reveal whether there is the latent dose–
response relation between ELF-EMF exposure and the
alteration of CNS function.
Acknowledgments This work was supported by the Guangdong
Power Grid Corporation, Guangzhou, China.
Conflict of interest The authors declare they have no competing
financial interests.
References
1. McNamee DA, Legros AG, Krewski DR, Wisenberg G, Prato FS,
Thomas AW (2009) A literature review: the cardiovascular
effects of exposure to extremely low frequency electromagnetic
fields. Int Arch Occup Environ Health 82:919–933
2. Corbacio M, Brown S, Dubois S, Goulet D, Prato FS, Thomas
AW, Legros A (2011) Human cognitive performance in a 3 mT
power-line frequency magnetic field. Bioelectromagnetics 32:
620–633
3. Podd J, Abbott J, Rowland A, Kazantzis N (2002) Brief exposure
to a 50 Hz, 100 lT magnetic field: effects on reaction time,
accuracy, and recognition memory. Bioelectromagnetics 23:
189–195
4. Legros A, Beuter A (2005) Effect of a low intensity magnetic
field on human motor behavior. Bioelectromagnetics 26:657–669
5. Legros A, Corbacio M, Beuter A, Modolo J, Goulet D, Prato FS,
Thomas AW (2012) Neurophysiological and behavioral effects of
a 60 Hz, 1800 lT magnetic field in humans. Eur J Appl Physiol
112:1751–1762
6. Keetley V, Wood A, Sadafi H, Stough C (2001) Neuropsycho-
logical sequelae of 50 Hz magnetic fields. Int J Radiat Biol
77:735–742
7. Preece AW, Wesnes KA, Iwi GR (1998) The effect of a 50 Hz
magnetic field on cognitive function in humans. Int J Radiat Biol
74:463–470
8. Kazantzis N, Podd J, Whittington C (1996) Acute effects of
50 Hz, 100 lT magnetic field exposure on visual duration dis-
crimination at two different times of the day. Bioelectromagnetics
19:310–317
9. Legros A, Gaillot P, Beuter A (2006) Transient effect of low-
intensity magnetic field on human motor control. Med Eng Phys
28:827–836
10. Legros A, Beuter A (2006) Individual subject sensitivity to
extremely low frequency magnetic field. Neurotoxicology 27:
534–546
11. Nevelsteen S, Legros JJ, Crasson M (2007) Effects of information
and 50 Hz magnetic fields on cognitive performance and reported
symptoms. Bioelectromagnetics 28:53–63
12. Delhez M, Legros JJ, Crasson M (2004) No influence of 20 and
400 lT, 50 Hz magnetic field exposure on cognitive function in
humans. Bioelectromagnetics 25:592–598
13. Cook MR, Graham C, Cohen HD, Gerkovich MM (1992) A
replication study of human exposure to 60 Hz fields: effects on
Neurobehavior measures. Bioelectromagnetics 13:261–285
14. Cook CM, Thomas AW, Prato FS (2002) Human electrophysio-
logical and cognitive effects of exposure to ELF magnetic and
ELF modulated RF and microwave fields: a review of recent
studies. Bioelectromagnetics 23:144–157
15. Frahm J, Mattsson MO, Simko M (2010) Exposure to ELF
magnetic field modulate redox related protein expression in
mouse macrophages. Toxicol Lett 192:330–336
16. Turkozer Z, Guler G, Seyhan N (2008) Effects of exposure to
50 Hz electric field at different strengths on oxidative stress and
Australas Phys Eng Sci Med (2014) 37:37–44 43
123
antioxidant enzyme activities in the brain tissue of guinea pigs.
Int J Radiat Biol 84:581–590
17. Rageh MM, El-Gebaly RH, El-Bialy NS (2012) Assessment of
genotoxic and cytotoxic hazards in brain and bone marrow cells
of newborn rats exposed to extremely low-frequency magnetic
field. J Biomed Biotechnol 2012:716023
18. Anger WK, Liang YX, Nell V, Kang SK, Cole D, Bazylewicz-
Walczak B, Rohlman DS, Sizemore OJ (2000) Lessons
learned—15 years of the WHO-NCTB: a review. Neurotoxi-
cology 21:837–846
19. Gauger JR (1985) Household appliance magnetic field survey.
IEEE Trans Power Appar Syst PAS 104:2436–2444
20. Gandhi OP, Kang G, Wu D, Lazzi G (2001) Currents induced in
anatomic models of the human for uniform and nonuniform power
frequency magnetic fields. Bioelectromagnetics 22:112–121
21. Nishimura T, Tada H, Guo X, Murayama T, Teramukai S, Okano
H, Yamada J, Mohri K, Fukushima M (2011) A 1-lT extremely
low-frequency electromagnetic field vs. sham control for mild-to-
moderate hypertension: a double-blind, randomized study. Hy-
pertens Res 34:372–377
22. Crasson M (2003) 50–60 Hz electric and magnetic field effects
on cognitive function in humans: a review. In: Weak ELF electric
field effects in the body. Proceedings of an International Work-
shop, Chilton, National Radiological Protection Board, March
2003. Radiat Prot Dosimetry 106:333–340
23. Trimmel M, Schweiger E (1998) Effects of an ELF (50 Hz, 1
mT) electromagnetic field (EMF) on concentration in visual
attention, perception and memory including effects of EMF
sensitivity. Toxicol Lett 96–97:377–382
24. Rubin GJ, Hillert L, Nieto-Hernandez R, van Rongen E, Oftedal
G (2011) Do people with idiopathic environmental intolerance
attributed to electromagnetic field display physiological effects
when exposed to electromagnetic field? A systematic review of
provocation studies. Bioelectromagnetics 32:593–609
25. Szemerszky R, Koteles F, Lihi R, Bardos G (2010) Polluted
places or polluted minds? An experimental sham-exposure study
on background psychological factors of symptom formation in
‘Idiopathic Environmental Intolerance attributed to electromag-
netic field’. Int J Hyg Environ Health 213:387–394
26. Liu X, Zhao L, Yu D, Ma S, Liu X (2013) Effects of extremely
low frequency electromagnetic field on the health of workers in
automotive industry. Electromagn Biol Med 32(4):551–559
27. Thuroczy G, Janossy G, Nagy N, Bakos J, Szabo J, Mezei G
(2008) Exposure to 50 Hz magnetic field in apartment buildings
with built-in transformer stations in Hungary. Radiat Prot
Dosimetry 131(4):469–473
28. Valjus J, Hongisto M, Verkasalo P, Jarvinen P, Heikkila K,
Koskenvuo M (1995) Residential exposure to magnetic fields
generated by 110–400 kV power lines in Finland. Bioelectro-
magnetics 16(6):365–376
29. Hareuveny R, Kandel S, Yitzhak NM, Kheifets L, Mezei G
(2011) Exposure to 50 Hz magnetic fields in apartment buildings
with indoor transformer stations in Israel. J Expo Sci Environ
Epidemiol 21(4):365–371
30. Ztoupis IN, Gonos IF, Stathopulos IA (2013) Uncertainty eval-
uation in the measurement of power frequency electric and
magnetic fields from AC overhead power lines. Radiat Prot
Dosimetry 157(1):11–21
31. Di Loreto S, Falone S, Caracciolo V, Sebastiani P, D’Alessandro
A, Mirabilio A, Zimmitti V, Amicarelli F (2009) Fifty hertz
extremely low-frequency magnetic field exposure elicits redox
and trophic response in rat-cortical neurons. J Cell Physiol
219:334–343
32. da Cruz MT, Cardoso AL, de Almeida LP, Simoes S, de Lima
MC (2005) Tf-lipoplex-mediated NGF gene transfer to the CNS:
neuronal protection and recovery in an excitotoxic model of brain
injury. Gene Ther 12:1242–1252
33. Saunders RD, Jefferys JG (2007) A neurobiological basis for ELF
guidelines. Health Phys 92:596–603
34. Hodgkin AL, Huxley AF (1952) A quantitative description of
membrane current and its application to conduction and excita-
tion in nerve. J Physiol 117:500–544
35. Z’Graggen WJ, Bostock H (2008) Nerve membrane excitability
testing. Eur J Anaesthesiol Suppl 42:68–72
44 Australas Phys Eng Sci Med (2014) 37:37–44
123
