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sustainability
Article
Exposure to 50 Hz Magnetic Fields in Homes and
Areas Surrounding Urban Transformer Stations in
Silla (Spain): Environmental Impact Assessment
Enrique A. Navarro-Camba 1, *ID , Jaume Segura-García2ID and Claudio Gomez-Perretta 3
1IRTIC, Universitat de València, C/. Catedrático JoséBeltran, 2, 46980 Paterna, Spain
2
Department Informática, ETSE, Universitat de València, Avd. de la Universidad S/N, 46100 Burjassot, Spain;
jaume.segura@uv.es
3Hospital Universitario La Fe, Avd. de Fernando Abril Martorell, 106, 46026 València, Spain;
gomez_cla@gva.es
*Correspondence: Enrique.navarro@uv.es; Tel.: +34-96-354-4794
Received: 30 June 2018; Accepted: 25 July 2018; Published: 27 July 2018
Abstract:
Exposure to extremely low frequency electromagnetic fields (ELFs) is almost inevitable
almost anywhere in the world. An ELF magnetic field (ELF-MF) of around 1 mG = 0.1
µ
T is typically
measured in any home of the world with a certain degree of development and well-being. There is
fear and concern about exposure to electromagnetic fields from high- and medium-voltage wiring
and transformer stations, especially internal transformer stations (TSs), which in Spain are commonly
located inside residential buildings on the ground floor. It is common for neighbors living near
these stations to ask for stations to be moved away from their homes, and to ask for information
about exposure levels and their effects. Municipality is the closest administration to the citizens that
must solve this situation, mediating between the citizens, the utility companies and the national
administration. In this case, the municipality of Silla (València, Spain) wanted to know the levels
of exposure in the dwellings annexed to the TSs, to compare them with Spanish legislation and the
recommendations coming from epidemiological studies. This article presents the first systematic
campaign of ELF-MF measurements from TSs carried out in a Spanish city. Many measurements
were carried out in the rooms of the apartments doing spatial averages of spatial grid measurements.
Measurements are made in the bed and bedrooms and a weighted average and an environmental
impact indicator were obtained for each location. We found that old TSs usually provide the highest
peak exposure levels. A notable result of this work is that approximately one quarter of the population
living above or next to a TS would be exposed to a weighted MF level greater than 0.3
µ
T, and that
about a 10% of this population would not be able to relocate their bedroom or living room to minimize
the level of exposure.
Keywords:
ELF-MF; magnetic field exposure; environmental impact EMFs; urban transformer
stations; transformer stations
1. Introduction
Exposure to extremely low frequency electromagnetic fields (ELFs) is almost inevitable almost
anywhere in the world in populations with a certain degree of development and well-being. Exposure
in homes comes from home wiring but mainly from electrical and electronic appliances and equipment
connected to the grid within the home. Typically, an extremely low frequency magnetic field (ELF-MF)
of around 1 mG (0.1
µ
T), 50 Hz, is detected inside a typical house in Spain [
1
,
2
]. Normally there is
more magnetic field where there is a higher consumption of electric current, and these higher levels
are mainly observed in the kitchen, where the refrigerator is always connected, but consumes power
Sustainability 2018,10, 2641; doi:10.3390/su10082641 www.mdpi.com/journal/sustainability
Sustainability 2018,10, 2641 2 of 11
when the compressor is started up, the electric stove consumes power by resistance or induction,
and the electric oven, the extractor fan, the various small electrical appliances and the microwave oven
consumes power when started up from time to time. It is worth mentioning that of all of them it is
the microwave that produces the greatest magnetic induction in the kitchen by far with respect to
other household appliances and this is due to its high power consumption to power the magnetron,
when the microwave oven is turned on the MF exceeds 0.5
µ
T in almost half of the kitchen, although
this exposure is of short duration since the microwave is running for only a few minutes.
Other sources of exposure that go unnoticed by residents and are under their control are speakers
on stereos and radio receivers connected to the wall socket, which in some cases are in the bedroom
headboards. However, there is fear and concern about possible exposure to electromagnetic fields from
high- and medium-voltage wiring and transformer stations, especially internal transformer stations
(TSs), which in Spain are commonly located inside residential buildings on the ground floor. In these
cases, the fear comes from a combination of ignorance of exposure levels and lack of control over them,
which obviously depends on the supply of electrical power to communities and industrial and service
areas through wiring and TSs.
Is there an objective basis for justifying residents’ concerns? From an epidemiological standpoint,
a first study in 1979 [
3
] found that the pediatric population living near high-current wiring configurations
doubled the risk of leukemia. These epidemiological results were confirmed in two combined
analyses [
4
], which with a cut-off level of 0.3
µ
T found an odd ratio (OR) of 1.7 (95% CI: 1.2–2.3),
and with a cut-off level of 0.4
µ
T [
5
] observed an OR of 2.0 (95% CI: 1.3–3.1). Based on these
epidemiological studies, the International Agency for Research on Cancer (IARC) classifies ELF
as a possible human carcinogen, classification 2B, based on these studies in which there is “limited”
epidemiological evidence for a causal relationship between exposure to an ELF magnetic field and
childhood leukemia. Finally, the results of Wertheimer and Leeper [
3
], Greenland et al. [
4
] and
Ahlbom et al. [
5
] are confirmed by Kheifets et al. [
6
] in a combined analysis of seven studies using the
reference of 0.3
µ
T. However, the epidemiological results are not supported by a known biophysical
mechanism, and various confounding arguments are put forward to explain this association, which is
ruled out (Greenland, [
7
]; Greenland and Kheifets, [
8
]), and corrections in the exposure estimation,
when taken into account, increase the level of association rather than subtract the level of association
(Greenland, [7]; Kheifets and Oksuzyan, [9]).
One of the problems encountered in epidemiological studies is the scarcity of individuals with
high exposure and the low participation of controls to carry out the measures. One of the alternatives
proposed to resolve this situation and improve epidemiological studies is the proposal to study the
buildings containing TSs, in particular TSs inside residential buildings on the ground floor (Kheifets
and Oksuzyan, [
8
]). In the TSs, the wiring connections and current bars converge, which when carrying
large currents generate high MF values that decay rapidly with the distance. Therefore, the attached
dwellings, next to or above the TSs, would result in strong exposure for their residents, while for more
distant dwellings the level of exposure would be much lower. The knowledge of the level of ELF-MF
in the dwellings of the buildings with internal TS on the ground floor would allow the establishment
of some mathematical statistical models to know the level of exposure of the residents retrospectively,
knowing the building where their dwelling is located and the location of their dwelling without
the need to measure in each case. This would greatly facilitate environmental and epidemiological
studies, eliminate the control selection biases, and eliminate confounding agents, such as the ionized air
surrounding the high-voltage cables, which would not be present in the dwellings attached to the TSs.
Measurement campaigns have been carried out in Finland, Israel, Hungary, and Switzerland to analyze
a possible exposure assessment procedure (Ilonen et al. [
10
]; Hareuveny et al. [
11
]; Szabo et al. [
12
];
Thuroczy et al. [
13
]; Martin Rösli et al. [
14
]); in these works, in the framework of the TransExpo
project [
15
–
18
], specific measurements have been made in apartments in buildings on which TSs are
located on the ground floor.
Sustainability 2018,10, 2641 3 of 11
In this work, an ELF-MF measurement campaign carried out in Silla, (València), is presented.
Silla is a city in the autonomous community of València (Spain), located in the county of L’Horta Sud,
and with a population of 18,440 according to 2017 data from the National Institute of Statistics [
19
].
The municipality of Silla promoted this work in response to the demand of a large part of the affected
residents, concerned about the possible exposure of their homes. The City Council of Silla proposed to
carry out a detailed analysis of the exposure levels of residents in their homes, to assess the possible
environmental impact with respect to the levels previously mentioned from epidemiological studies.
A detailed analysis of MF exposure in each room of each home was necessary because TSs are
localized sources of MF, unlike other structures such as medium- and high-voltage power transmission
lines. The exposure in the adjoining dwellings, either above or to the sides, will be a localized exposure.
It is possible that only some rooms are subject to high exposure, and the other rooms may have normal
levels of MF from a domestic environment. Depending on the type of TS, the structure of the building,
age, and the type of housing, it is also possible that almost all the housing is subjected to high levels of
MF. This paper aims to provide information in this regard, and the usefulness would be in its possible
extrapolation to the general population under these circumstances.
Finally, there are also homes in large buildings whose construction planning has allowed for the
existence of a meter cabinet attached to some part of the community’s home. In these cases, all the
electrical current consumed by the community passes through this cabinet, giving rise to high levels
of MF in these parts of the home. This situation has also been considered, in particular for the future
perspective that the remote management of meters by PLC signal [
20
] also increases radiation levels in
these areas.
This article presents the first systematic campaign of ELF-MF measures from TSs carried out in
a Spanish city. To our knowledge, this would be the first article in which the measurements obtained
from spatial averages in grids are presented, in each room, where average exposure values are
calculated with descriptive statistics of the measurements in all the dwellings, and the environmental
impact is analyzed taking into account the number of rooms in each dwelling. This work would be
a further contribution to the knowledge of the exposure levels of residents, and would complement all
the work done in this area to date in the world.
2. Materials and Methods
A census of all the TSs in the town of Silla (València, Spain) was carried out. In the elaboration
of this census the TSs on industrial land, the areas of agricultural use and in general all the TSs
of non-residential use were omitted. There were 31 TSs in the urban area of Silla, throughout the
municipality, discounting the TSs in the industrial and agricultural areas. Of these TSs, one supplied
power to a communications center, one supplied power to a supermarket, and in both cases its
maintenance was managed by their respective companies. The remaining 29 TSs supply energy to
various areas of the city and were managed and maintained by the electricity distribution company.
Most of the TSs were found embedded in the ground floors of buildings, of which only two had
dwellings next door embedded in the structure of a building, one TS was found in a single-story house
with dwellings on the sides, one very old tower TS was found without adjoining dwellings, and three
TSs were found in prefabricated concrete cases in landscaped spaces away from dwellings.
With the support of municipal officials, the residents of the houses above or next to the TSs
were contacted, informed of the campaign of measures to be carried out by the municipality and
asked for written permission to access the houses to carry out the measurements. Information was
also collected on the number of persons residing in the dwelling, adults and children, and other
information for future statistical treatment. The census of the TSs with the addresses of the dwellings
with authorization to measure and the respective contact telephone numbers were provided to our
team to proceed with the measurement campaign.
It was decided that the measures had to show the most unfavorable situation, the one in which
the levels of MF were expected to be higher, for that reason the temporary range of measurements was
Sustainability 2018,10, 2641 4 of 11
chosen from 18:30 to 22:00 in which the energy consumption was assumed to reach maximum levels
due to the fact that the residents have returned from their working day, and the families are in their
homes, cooking, watching television, and doing their domestic chores with the electrical appliances
with the consequent consumption of electrical energy.
The campaign of measures started in the last week of September 2017 and lasted until February
2018. Residents were first phoned, and the visit was arranged, and then visited. The study was
approved by the ethics committee of the University of València.
The measures were carried out with the EFA-300 [
21
]. The measurements carried out in each
house aim to show the ELF-MF landscape by optimizing the measurement time in each case.
Upon entering the house, a quick inspection of the MF levels was carried out in all its accessible
rooms. The measurements were carried out following the “walking procedure”, widely used in noise
measurement campaigns and usually followed by our technicians since 2000 [
1
]. In measurements with
the EFA-300, it is measured at each step and stored in memory and/or recorded. The meter is held by
hand approximately 1.0 m above the ground. In each zone it is measured in a spatial grid covering the
area. If high levels of magnetic induction are detected, the source is identified and measured in distance
and around the source to limit the area of greatest exposure. The measures are regularly distributed in
the areas under study to identify the sources of emissions and their extent. If vertical field gradients
are discovered, the sources are searched and the field levels on the ground are characterized. In this
way, any MF source is detected a properly located.
Measurements were not recorded in spaces where the measurements made were negligible or
within the normal levels of a dwelling or open space away from TSs or other foreign sources of MF.
Finally, it was not measured in inaccessible spaces, spaces with furniture and fixtures that prevent
access and use on a regular basis.
Typical MF measurements in a house in Spain are around 0.1
µ
T. Values above 0.3
µ
T are found
very close to appliances that are in operation, the refrigerator when the compressor is running,
the washing machine, the electric stove either by resistance or induction, and especially the microwave
oven. These measurements are found in the kitchen, which is usually the area of the house with the
highest exposure of ELF-MF.
3. Results
Of the total number of encountered TSs, one was excluded from the study because the residents
living above the TSs refused to collaborate in the study. Of the remaining TSs counted, there were:
1 TS in a recently constructed concrete case on the periphery of a school playground, 2 TS in two
prefabricated concrete boxes in a newly developed area less than 10 years old, see Figure 1, away from
the building blocks in the center of a landscaped area, 1 TS next to a block of recent buildings less
than 10 years old, very close to a ground-floor house. There is a very old tower TS from before 1960,
away from a block of very old houses (see Figure 1). There is also 1 TS located on the ground floor
of an old house, possibly from around 1960, purchased and fitted out by the electricity distribution
company. Finally, there is 1 TS attached to the corner of a block of old buildings from before 1980;
this TS has apartments next to it and no apartments on top of it. In total we counted 7 TSs that would
result in high levels of magnetic induction in areas of easy access from the sides. Finally, we added
to the studio an apartment that had a panel of electricity meters attached to the outside wall of
an area of the house, which would also lead to high levels of MF in lateral access areas, in particular
a ground-floor dwelling. The rest up to the totality are TSs located in ground-floor spaces, at street
level, which have dwellings on top, and parking or commercial areas on their sides.
The installations are normally operated by the electricity supply company. When developing
and building, specifications are given to the developer-builder agent to prepare the spaces and install
the TSs, which are then transferred to the company that supplies the electricity and that, after the
assignment, takes care of their maintenance. These specifications have changed in the last 60 years
and this has given rise to different types of spaces, with different spacing between equipment walls
Sustainability 2018,10, 2641 5 of 11
and ceiling where obviously the considerations of maximum use of space have prevailed, without
going into assessing aspects related to the minimization or shielding of the magnetic field. In response
to residents’ response to possible exposure to magnetic fields, new developments have evolved and
no longer have internal TSs in new buildings, especially sensitive areas such as schools. If they have
sufficient land area, TSs are usually installed in the center of avenues or garden areas. TSs located on
the ground floors of old buildings in downtown area are difficult to modify due to the lack of spaces,
in these cases the minimization of ELF-MF in the adjacent spaces requires a change in the configuration
of the wiring or the TS technology itself.
Sustainability 2018, 10, x FOR PEER REVIEW 5 of 11
evolved and no longer have internal TSs in new buildings, especially sensitive areas such as schools.
If they have sufficient land area, TSs are usually installed in the center of avenues or garden areas.
TSs located on the ground floors of old buildings in downtown area are difficult to modify due to the
lack of spaces, in these cases the minimization of ELF-MF in the adjacent spaces requires a change in
the configuration of the wiring or the TS technology itself.
(a) (b)
Figure 1. The oldest and most recent TS where it has been measured: (a) Tower with very old TS,
more than 60 years old; (b) Precast concrete box with very recent TS, less than 10 years old.
Two of the TSs under study did not belong to the electricity supply company. In Spain there is
the possibility that a TS may not belong to the supply company, in this case the supply company
conducts the electricity in medium-voltage to the TS, and the TS owners are responsible for its
management and proper maintenance. Normally, to avoid maintenance costs, the promoters of the
installation pass it on to the electricity supply company.
Table 1 shows the results of the measurements in the 31 locations. The age is indicated in ten
years intervals, is known by municipal technicians and is easily deduced from the observation of the
techniques and building materials used in the construction. In Table 1, it is indicated whether the TS
is below or next to it, and the descriptive statistical parameters of the measurements are presented in
microTesla (μT), maximum, minimum, mean, median and standard deviation. The number of
spaces where it has been measured is indicated, and finally the average value of the measurements
made in the bed or beds of the most affected spaces are also presented.
Table 1. Summary of the measures in 31 dwellings. The spaces column indicates the number of
rooms or spaces in the dwelling that have been measured.
Code Location Age Mean Numbe
r
Max Min Std Median Spaces Bed
A1 Above 10 0.02 48 0.03 0.02 0.00 0.02 1 0.02
A2 Above 10 0.02 84 0.03 0.02 0.00 0.02 2 0.02
A3 Above 10 0.09 97 0.29 0.01 0.08 0.06 3 0.24
A4 Above 50 0.42 196 3.05 0.10 0.42 3.01 5 0.35
A5 Above 10 0.02 134 0.15 0.00 0.03 0.01 4 0.01
A6 Above 60 0.26 99 0.85 0.01 0.25 0.13 3 0.04
A7 Above 10 0.15 168 0.89 0.01 0.11 0.13 3 0.17
A8 Above 10 0.16 120 1.80 0.03 0.17 0.14 3 0.31
A9 Above 10 0.17 88 0.26 0.05 0.06 0.19 2 0.37
A10 Above 10 0.18 128 0.53 0.02 0.15 0.11 5 0.01
A11 Above 30 0.33 185 0.98 0.04 0.24 0.30 5 0.62
A12 Same floor 60 0.27 88 1.57 0.00 0.31 0.18 2 0.32
A13 Above 30 0.19 105 0.31 0.10 0.04 0.19 2 0.25
A14 Above 40 0.17 72 0.26 0.08 0.04 0.15 1 0.17
A15 Same floor 20 0.51 114 2.42 0.10 0.47 0.33 3 0.51
A16 Above 40 0.25 108 0.51 0.03 0.13 0.24 2 0.00
A17 Same floor 10 0.15 158 0.42 0.05 0.07 0.12 4 0.29
Figure 1.
The oldest and most recent TS where it has been measured: (
a
) Tower with very old TS,
more than 60 years old; (b) Precast concrete box with very recent TS, less than 10 years old.
Two of the TSs under study did not belong to the electricity supply company. In Spain there is the
possibility that a TS may not belong to the supply company, in this case the supply company conducts
the electricity in medium-voltage to the TS, and the TS owners are responsible for its management and
proper maintenance. Normally, to avoid maintenance costs, the promoters of the installation pass it on
to the electricity supply company.
Table 1shows the results of the measurements in the 31 locations. The age is indicated in ten
years intervals, is known by municipal technicians and is easily deduced from the observation of the
techniques and building materials used in the construction. In Table 1, it is indicated whether the TS is
below or next to it, and the descriptive statistical parameters of the measurements are presented in
microTesla (
µ
T), maximum, minimum, mean, median and standard deviation. The number of spaces
where it has been measured is indicated, and finally the average value of the measurements made in
the bed or beds of the most affected spaces are also presented.
Table 1.
Summary of the measures in 31 dwellings. The spaces column indicates the number of rooms
or spaces in the dwelling that have been measured.
Code Location Age Mean Number Max Min Std Median Spaces Bed
A1 Above 10 0.02 48 0.03 0.02 0.00 0.02 1 0.02
A2 Above 10 0.02 84 0.03 0.02 0.00 0.02 2 0.02
A3 Above 10 0.09 97 0.29 0.01 0.08 0.06 3 0.24
A4 Above 50 0.42 196 3.05 0.10 0.42 3.01 5 0.35
A5 Above 10 0.02 134 0.15 0.00 0.03 0.01 4 0.01
A6 Above 60 0.26 99 0.85 0.01 0.25 0.13 3 0.04
A7 Above 10 0.15 168 0.89 0.01 0.11 0.13 3 0.17
A8 Above 10 0.16 120 1.80 0.03 0.17 0.14 3 0.31
A9 Above 10 0.17 88 0.26 0.05 0.06 0.19 2 0.37
A10 Above 10 0.18 128 0.53 0.02 0.15 0.11 5 0.01
Sustainability 2018,10, 2641 6 of 11
Table 1. Cont.
Code Location Age Mean Number Max Min Std Median Spaces Bed
A11 Above 30 0.33 185 0.98 0.04 0.24 0.30 5 0.62
A12 Same floor 60 0.27 88 1.57 0.00 0.31 0.18 2 0.32
A13 Above 30 0.19 105 0.31 0.10 0.04 0.19 2 0.25
A14 Above 40 0.17 72 0.26 0.08 0.04 0.15 1 0.17
A15 Same floor 20 0.51 114 2.42 0.10 0.47 0.33 3 0.51
A16 Above 40 0.25 108 0.51 0.03 0.13 0.24 2 0.00
A17 Same floor 10 0.15 158 0.42 0.05 0.07 0.12 4 0.29
A18 Above 10 0.14 115 0.33 0.04 0.09 0.12 2 0.36
A19 Above 40 0.38 168 1.51 0.04 0.27 0.37 3 0.07
A20 Above 50 7.03 20 20.08 0.87 6.17 4.31 1 0.42
A21 Above 10 0.04 72 0.10 0.00 0.02 0.04 3 0.03
A22 Above 50 0.15 277 0.43 0.01 0.11 0.11 5 0.07
A23 Above 40 0.12 112 0.27 0.01 0.08 0.12 2 0.02
A24 Above 10 0.03 196 0.10 0.00 0.02 0.02 3 0.04
A25 Same floor 50 0.07 253 0.28 0.01 0.06 0.03 7 0.30
A26 Above 50 0.33 327 0.89 0.03 0.23 0.29 4 0.88
A27 Same floor 10 0.35 94 0.83 0.15 0.14 0.32 1 0.00
A28 Same floor 10 0.35 94 0.83 0.15 0.14 0.32 1 0.00
A29 Same floor 60 0.03 48 0.07 0.01 0.02 0.02 2 0.03
A30 Above 40 0.07 144 0.21 0.04 0.02 0.07 5 0.07
A31 Same floor 10 0.02 90 4.10 0.01 0.44 0.24 3 0.02
A31 data are obtained in the apartment under the influence of the meters cabinet attached the exterior of the
kitchen wall.
Our measurements are within the order of magnitude of the measurements carried out in
Finland, Switzerland, Hungary, Israel, Bulgaria, and The Netherlands [
10
–
18
], in the framework
of the TransExpo Project [
15
]. The average of the average values gives us an average value of 0.4
µ
T
for the dwellings above or adjacent to the TS. This result is interesting because it almost coincides
with the average values obtained in Israel, Bulgaria and Netherlands [
15
], and is close to the average
of Finland and Switzerland, which show average values of 0.56 (0.17–1.55), and 0.59 (0.16–1.30).
However, our result is about half that of Hungary, 0.98 (0.18–3.68). The measurements were made
in circumstances of minimal electricity consumption within each dwelling, i.e., without cooking
stoves or baking ovens, or heating electric stoves. The consumption in the houses was caused by
the luminaires and occasionally the televisions turned on. This is important in order to have some
assurance that the measure being taken has its source in the TS, and not in the wiring of the house
itself. These circumstances are not obvious in the previous works [
10
–
18
]. Also, when the successive
averages are carried out, the values obtained are smoothed out and do not appear to be so high;
however, they are high in some areas where values of 2–20
µ
T were reached. There were circumstances
of very high magnetic fields in spatially reduced areas where residents occupied these areas in very
short periods of time, and cases where the magnetic field was not excessively high, but affected
virtually the entire dwelling. These special circumstances have been assessed with the introduction of
the weighted average and the environmental impact factor to be introduced below.
Figure 2shows the location of TSs on a map of Silla, where the interpolated values are shown in
a color code using a geostatistical procedure [
18
,
19
], and Figure 3shows the mean value at each place
(from Table 1) with a red line showing the limit level of 0.3 µT.
From the measures in Table 1, a weighted exposure level is calculated that takes into account
the possible permanence of residents in each part of the dwelling and bedroom. The average level of
exposure in the rooms and in the bed is taken into account, assuming that the resident spends 12 h in
his or her home and of these, 8 h rests in the bedroom. The averaged measurement in the rooms is
multiplied by 1/3 and the measure in the bed is multiplied by 2/3, the sum of both amounts gives us
the weighted average in each dwelling. The weighted average is shown in Figure 4, with a red line
showing the limit level of 0.3 µT.
Sustainability 2018,10, 2641 7 of 11
When residents are informed of the levels of exposure in each room, residents may carry out
individual actions to reduce exposure, which would be of a temporary nature, pending other definitive
minimization actions by the company in charge of TS maintenance. If the house has many rooms and
mostly MF levels are low there are many possibilities for relocation. Based on this, we developed
an environmental impact indicator that not only evaluates the weighted exposure level, but also the
possibility of minimizing the exposure with individual actions of residents. For example, the area with
high exposure is a single room or only the bedroom, but there are other rooms with low or normal
levels, in this case the resident can change the bedroom and this indicator would score 1, on the
extreme side this indicator would be 3 for high exposure in all rooms with no possibility of relocation.
The environmental impact is calculated by multiplying the weighted exposure times the score and
divided by 0.3 (the maximum). The environmental impact calculated in this way is shown in Figure 5,
with a red line showing the limit level of 2.5. The value 2.5 is a reference value in a home with half of
the rooms well below the recommended levels (0.3 µT).
Sustainability 2018, 10, x FOR PEER REVIEW 7 of 11
possibility of relocation. The environmental impact is calculated by multiplying the weighted
exposure times the score and divided by 0.3 (the maximum). The environmental impact calculated in
this way is shown in Figure 5, with a red line showing the limit level of 2.5. The value 2.5 is a
reference value in a home with half of the rooms well below the recommended levels (0.3 μT).
Figure 2. Map of the city of Silla, with the location of the TSs. The color shows the average MF values
interpolated with the geostatistical methodology used by our team in the analysis of noise levels
[22,23].
Figure 3. Mean value of the measured MF versus the age of the TS and the building were the TS is
embedded.
Figure 4. Weighted average of the measured MF versus the age of the TS and the building were the
TS is embedded.
Figure 2.
Map of the city of Silla, with the location of the TSs. The color shows the average MF values
interpolated with the geostatistical methodology used by our team in the analysis of noise levels [
22
,
23
].
Sustainability 2018, 10, x FOR PEER REVIEW 7 of 11
possibility of relocation. The environmental impact is calculated by multiplying the weighted
exposure times the score and divided by 0.3 (the maximum). The environmental impact calculated in
this way is shown in Figure 5, with a red line showing the limit level of 2.5. The value 2.5 is a
reference value in a home with half of the rooms well below the recommended levels (0.3 μT).
Figure 2. Map of the city of Silla, with the location of the TSs. The color shows the average MF values
interpolated with the geostatistical methodology used by our team in the analysis of noise levels
[22,23].
Figure 3. Mean value of the measured MF versus the age of the TS and the building were the TS is
embedded.
Figure 4. Weighted average of the measured MF versus the age of the TS and the building were the
TS is embedded.
Figure 3.
Mean value of the measured MF versus the age of the TS and the building were the TS
is embedded.
Sustainability 2018,10, 2641 8 of 11
Sustainability 2018, 10, x FOR PEER REVIEW 7 of 11
possibility of relocation. The environmental impact is calculated by multiplying the weighted
exposure times the score and divided by 0.3 (the maximum). The environmental impact calculated in
this way is shown in Figure 5, with a red line showing the limit level of 2.5. The value 2.5 is a
reference value in a home with half of the rooms well below the recommended levels (0.3 μT).
Figure 2. Map of the city of Silla, with the location of the TSs. The color shows the average MF values
interpolated with the geostatistical methodology used by our team in the analysis of noise levels
[22,23].
Figure 3. Mean value of the measured MF versus the age of the TS and the building were the TS is
embedded.
Figure 4. Weighted average of the measured MF versus the age of the TS and the building were the
TS is embedded.
Figure 4.
Weighted average of the measured MF versus the age of the TS and the building were the TS
is embedded.
Sustainability 2018, 10, x FOR PEER REVIEW 8 of 11
Figure 5. Environmental impact of MF at each location versus the age of the TS and the building were
the TS is embedded.
4. Discussion
The obtained results must be analyzed according to the MF measured levels and the affected
area. Obviously, all the measures are below the levels set by Spanish legislation, 100 μT at 50 Hz,
which is Royal Decree 1066/2001, based on the guidelines of the European recommendation [24].
There are 20 dwellings, 65%, with maximum values above the recommendation of 0.3 μT, but
the maximum values can be in very small areas, or areas of low traffic and therefore have little
environmental impact. In this case it is necessary to take into account the average values and average
values weighted according to the temporary occupation in each room. There are six homes, 22.2% of
the 27 locations, with mean values above the recommendation of 0.3 μT. These are the
measurements in A4-11-15-19-20-26. Of these measurements, two, A27-28, correspond to TS in
isolated concrete boxes and these are transit zones. A15 is a TS that has been installed in an old
single-family house but that affects recent neighboring houses, is not the most common case. Of
these six sites, four correspond to buildings dating from 1960–1980. This would indicate that the
levels exceeding the recommendations for housing would be mainly in buildings more than 40 years
old. Although it would not be the responsibility of the utility company, but of the construction
developer, the guidelines are set by the utility company, and the developer always tries to scratch
the square meters of construction to the maximum to obtain the maximum return on the investment
made. On the other hand, the possible environmental sensitivity in Spain 30 years ago is not the
same as it is at the moment and this is reflected in the measures carried out: the most recent
installations tend to have less impact on the neighboring houses. The sites of the new A27-28
urbanization have the TSs in prefabricated concrete cabins far from the houses, and the recent
constructions that do not have space to relocate outside the buildings show lower levels due to a
combination of a better cabling layout and a higher height of the first floor.
We then assess the impact on residents based on the weighted average level. The weighted
average level takes into account the average level of exposure in the rooms which is multiplied by
1/3 and the measure in the bed which is multiplied by 2/3, the sum of both amounts gives us the
weighted average in each dwelling. Figure 4 shows that the weighted mean of ELF-MF levels varies
between a minimum of 0.01 and a maximum of 0.75, we find seven dwellings that reach weighted
average levels above 0.3 μT, i.e., we find that about one quarter of the residents living above or next
to a TS have a weighted average exposure higher than the 0.3 μT.
The possibility of a hypothetical relocation of the bedroom or of the areas of greater
permanence within the dwelling has also been assessed to reduce the weighted exposure level, is
done by assigning an environmental impact index. The environmental impact assesses the
Figure 5.
Environmental impact of MF at each location versus the age of the TS and the building were
the TS is embedded.
4. Discussion
The obtained results must be analyzed according to the MF measured levels and the affected area.
Obviously, all the measures are below the levels set by Spanish legislation, 100
µ
T at 50 Hz, which is
Royal Decree 1066/2001, based on the guidelines of the European recommendation [24].
There are 20 dwellings, 65%, with maximum values above the recommendation of 0.3
µ
T, but the
maximum values can be in very small areas, or areas of low traffic and therefore have little environmental
impact. In this case it is necessary to take into account the average values and average values
weighted according to the temporary occupation in each room. There are six homes, 22.2% of the
27 locations, with mean values above the recommendation of 0.3
µ
T. These are the measurements in
A4-11-15-19-20-26. Of these measurements, two, A27-28, correspond to TS in isolated concrete boxes and
these are transit zones. A15 is a TS that has been installed in an old single-family house but that affects
recent neighboring houses, is not the most common case. Of these six sites, four correspond to buildings
dating from 1960–1980. This would indicate that the levels exceeding the recommendations for housing
would be mainly in buildings more than 40 years old. Although it would not be the responsibility of
the utility company, but of the construction developer, the guidelines are set by the utility company,
and the developer always tries to scratch the square meters of construction to the maximum to obtain
the maximum return on the investment made. On the other hand, the possible environmental sensitivity
Sustainability 2018,10, 2641 9 of 11
in Spain 30 years ago is not the same as it is at the moment and this is reflected in the measures carried
out: the most recent installations tend to have less impact on the neighboring houses. The sites of the
new A27-28 urbanization have the TSs in prefabricated concrete cabins far from the houses, and the
recent constructions that do not have space to relocate outside the buildings show lower levels due to
a combination of a better cabling layout and a higher height of the first floor.
We then assess the impact on residents based on the weighted average level. The weighted average
level takes into account the average level of exposure in the rooms which is multiplied by 1/3 and
the measure in the bed which is multiplied by 2/3, the sum of both amounts gives us the weighted
average in each dwelling. Figure 4shows that the weighted mean of ELF-MF levels varies between
a minimum of 0.01 and a maximum of 0.75, we find seven dwellings that reach weighted average
levels above 0.3
µ
T, i.e., we find that about one quarter of the residents living above or next to a TS
have a weighted average exposure higher than the 0.3 µT.
The possibility of a hypothetical relocation of the bedroom or of the areas of greater permanence
within the dwelling has also been assessed to reduce the weighted exposure level, is done by assigning
an environmental impact index. The environmental impact assesses the possibilities of relocation
to minimize, in addition to the weighted average level. The indicator of environmental impact on
residents varies between 0.03 and 6.96. We observe that it is 0.03 for the case of average levels well below
the recommendations and/or with large dwellings with reduced affected area, and the maximum
is 6.96 for a dwelling with high levels in all rooms and no possibility of relocation. The value 2.5 is
an intermediate value in a home with half of the rooms well below the recommended cut-off levels
(0.3
µ
T). From this quantification and from the results shown in Figure 5, we can see that we have
three cases, 11% of the total, which imply a high environmental impact on reported residents.
5. Conclusions
In this work we present the ELF-MF measurements made in dwellings located above or next
to TSs in a typical population of the Mediterranean coast. This work includes the first campaign of
measures of this nature carried out in Spain, among the first three in Europe, and four in the world.
It has been measured in all the rooms or spaces of the dwellings that have been accessible by measuring
a spatial average in a grid.
Without assessing whether the Spanish regulations respect the epidemiological evidence, simply
taking it as an obligatory reference, and using the city of Silla as a representative city of the whole
country, we could say that in every place in an urban environment MF levels comply with Spanish
regulations or “official standard”. The official standard in Spain is the Royal Decree 1066/2001, a copy
of the European recommendation [
24
], and ICNIRP (International Commission on Non-Ionizing
Radiation Protection) guidelines. The limits of official standard in Spain are 100 µT at 50 Hz.
The “recommended level” or “limit level” 0.3
µ
T comes from the bibliographical references
[2–9]
.
Other references sustaining this recommended level can be found in [
2
] or elsewhere [
25
].
The “recommended level” does not correspond to “official standard”. There is no consensus that
chronic exposure in the range >0.3
µ
T have any health effects. Health agencies acknowledge that there
is a suspicion that such effects may exist, but health agencies have not concluded that health problems
actually do exist [26].
We could say that apartments not attached or next to a TS have (associated to TS) MF levels far
below 0.3
µ
T. Also, we could say that the electrical meter cabinets have a limited influence on the
adjacent dwellings (A31 in Table 1), the weighted exposure and the environmental impact is minimal,
but this could depend on the configuration of the wiring relative to the dwelling, and it would be
necessary to study a greater number of cases to reach a more generalized conclusion.
A notable result of this work is that approximately a quarter of the population living above or
next to a TS would be exposed to a weighted MF greater than 0.3 µT.
Another important result of this work is that approximately 10% of this population would not be
able to relocate their bedroom or living room to minimize the level of exposure, i.e., after measuring
Sustainability 2018,10, 2641 10 of 11
and analyzing their home and looking at the possibilities of rearranging the activity in the home to
minimize exposure, about 10% of the homes would have difficulties with this possibility and possibly
residents would have to leave their home and look for a home that did not have a TS underneath it.
A positive outcome of the present campaign is that empirically is demonstrated that TSs in
spaces far from homes, in landscaped areas or in the center of wide avenues, have a negligible impact
in residents. Also, in existing constructions it is possible to minimize the exposure to MF by better
conditioning of the space around the TSs, more distance between TSs and houses, and possibly a better
layout of the wiring. It is shown empirically that modern TSs located on the ground floor of more
recent buildings definitively have the lowest environmental impact.
This work is of great interest regarding its use in future epidemiological studies. A large amount
of relevant information was collected that may be utilized in a future epidemiological study with
a proper statistical treatment.
Author Contributions:
Conceptualization, E.A.N.-C. and C.G.-P.; Methodology, E.A.N.-C.; Software, J.S.-G.;
Validation, E.A.N.-C. and J.S.-G.; Formal Analysis, E.A.N.-C.; Investigation, C.G.-P.; Resources, C.G.-P.; Writing-
Original Draft Preparation E.A.N.-C.; Writing-Review & Editing, E.A.N.-C. and J.S.-G.; Visualization, J.S.-G.;
Funding Acquisition, J.S.-G.
Funding: This research was funded by the Silla municipality.
Acknowledgments:
We are grateful for the support received from the councilman of territory, town planning and
infrastructure. We are also grateful for the help and support received from municipal officials and technicians
for the development of this work. Finally, the initiative of the municipal government is also recognized
and appreciated.
Conflicts of Interest:
The authors declare no conflict of interest. The funders had no role in the design of the
study; in the collection analyses, or interpretation of data; in the writing of the manuscript, and in the decision to
publish the results.
References
1.
Segura, J.; Navarro, E.A.; Sanchis, R.; Regalado, M. Caracterización del paisaje electromagnético en la
banda de 300 KHz a 3 GHz. In Proceedings of the XV Simposium Nacional de la URSI, Zaragoza, Spain,
13–15 September 2000; pp. 389–390.
2.
Ortega-Garcia, J.A.; Ferrís-Tortajada, J.; Navarro, E.A.; Garcia-Castell, J.; Soldin, O.; Berbel-Tornero, O.;
Rubalcava, L.; Fuster-Soler, J.L. Pediatric Health Effects due to Extremely Low Frequency Magnetic Fields.
Curr. Pediatr. Rev. 2009,5, 189–191.
3.
Wertheimer, N.; Leeper, E. Electrical wiring configurations and childhood cancer. Am. J. Epidemiol.
1979
,109,
273–284. [CrossRef] [PubMed]
4.
Greenland, S.; Sheppard, A.R.; Kaune, W.T.; Poole, C.; Kelsh, M.A. A pooled analysis of magnetic fields,
wire codes, and childhood leukaemia. Childhood Leukaemia EMF Study Group. Epidemiology
2000
,11,
624–634. [CrossRef] [PubMed]
5.
Ahlbom, A.; Day, N.; Feychting, M.; Roman, E.; Skinner, J.; Dockerty, J.; Linet, M.; McBride, M.; Michaelis, J.;
Olsen, J.H.; et al. A pooled analysis of magnetic fields and childhood leukaemia. Br. J. Cancer
2000
,83,
692–698. [CrossRef] [PubMed]
6.
Kheifets, L.; Ahlbom, A.; Crespi, C.; Draper, G.; Hagihara, J.; Lowenthal, R.; Mezei, G.; Oksuzyan, S.; Schüz, J.;
Swanson, J.; et al. Pooled analysis of recent studies on magnetic fields and childhood leukaemia. Br. J. Cancer
2010,103, 1128–1135. [CrossRef] [PubMed]
7.
Greenland, S. Multiple-bias modelling for analysis of observational data (with discussion). R. Stat. Soc.
2005
,
168, 267–306. [CrossRef]
8.
Greenland, S.; Kheifets, L. Leukemia attributable to residential magnetic fields: Results from analyses
allowing for study biases. Risk Anal. 2006,26, 471–481. [CrossRef] [PubMed]
9.
Kheifets, L.; Oksuzyan, S. Exposure assessment and other challenges in non-ionizing radiation studies of
childhood leukaemia. Radiat. Prot. Dosim. 2008,132, 139–147. [CrossRef] [PubMed]
10.
Ilonen, K.; Markkanen, A.; Mezei, G.; Juutilainen, J. Indoor transformer stations as predictors of residential
ELF magnetic field exposure. Bioelectromagnetics 2008,29, 213–218. [CrossRef] [PubMed]
Sustainability 2018,10, 2641 11 of 11
11.
Hareuveny, R.; Kandel, S.; Yitzhak, N.M.; Kheifets, L.; Mezei, G. Exposure to 50 Hz magnetic fields in
apartment buildings with indoor transformer stations in Israel. J. Expo. Sci. Environ. Epidemiol.
2010
,21,
365–371. [CrossRef] [PubMed]
12.
Szabo, J.; Janossy, G.; Thuroczy, G. Survey of residential 50 Hz EMF exposure from transformer stations.
Bioelectromagnetics 2007,28, 48–52. [CrossRef] [PubMed]
13.
Thuroczy, G.; Janossy, G.; Nagy, N.; Bakos, J.; Szabo, J.; Mezei, G. Exposure to 50 Hz magnetic field in
apartment buildings with built-in transformer stations in Hungary. Radiat. Prot. Dosim.
2008
,131, 469–473.
[CrossRef] [PubMed]
14.
Rösli, M.; Jenni, D.; Kheifets, L.; Mezei, G. Extremely low frequency magnetic field measurements in
buildings with transformer stations in Switzerland. Sci. Total Environ.
2011
,409, 3364–3369. [CrossRef]
[PubMed]
15.
TransExpo Project. Available online: http://www.emfs.info/research/studies/transexpo/ (accessed on
15 July 2018).
16.
Zaryabova, V.; Shalamanova, T.; Israel, M. Pilot study of extremely low frequency magnetic fields emitted by
transformers in dwellings. Social aspects. Electromagn. Biol. Med. 2013,32, 209–217. [CrossRef] [PubMed]
17.
Okokon, E.O.; Roivainen, P.; Kheifets, L.; Mezei, G.; Juutilainen, J. Indoor transformer stations and ELF
magnetic field exposure: Use of transformer structural characteristics to improve exposure assessment.
J. Expo. Sci. Environ. Epidemiol. 2014,24, 100–104. [CrossRef] [PubMed]
18.
Yitzhak, N.M.; Hareuveny, R.; Kandel, S.; Ruppin, R. Time dependence of 50 Hz magnetic fields in apartment
buildings with indoor transformer stations. Radiat. Prot. Dosim. 2012,149, 191–195. [CrossRef] [PubMed]
19.
Population of Silla (València, Spain), 2017. National Institute of Statistics. Available online: www.ine.es/
jaxiT3/Datos.htm?t=2903 (accessed on 28 June 2018).
20.
Galli, S.; Scaglione, A.; Wang, Z. For the grid and through the grid: The role of Power Line Communications
in the smart grid. Proc. IEEE 2008,99, 998–1027. [CrossRef]
21.
EFA-300 ELF Electromagnetic Meter Characteristics. Available online: www.narda-sts.us/pdf_files/EFA300_
DataSheet.pdf (accessed on 28 June 2018).
22.
Segura, J.; Montes-Suay, F.; Navarro, E.A. Método predictivo de la contaminación sonora espacio-temporal.
Aplicación a un municipio mediano: Algemesí(Valencia). Rev. Acúst. 2011,42, 26–31.
23.
Segura-Garcia, J.; Perez-Solano, J.J.; Cobos-Serrano, M.; Navarro-Camba, E.A.; Felici-Castell, S.; Soriano-Asensi, A.;
Montes-Suay, F. Spatial Statistical Analysis of Urban Noise Data from a WASN Gathered by an IoT System:
Application to a Small City. Appl. Sci. 2016,6, 380. [CrossRef]
24.
Council Recommendation 1999/519/EC on the Limitation of Exposure of the General Public to Electromagnetic
Fields (0 Hz to 300 GHz). Available online: https://osha.europa.eu/en/legislation/guidelines/council-
recommendation-1999-519-ec-on-the-limitation-of-exposure-of-the-general-public-to-electromagnetic-fields-
0-hz-to-300-ghz (accessed on 28 June 2018).
25.
Ferris Tortajada, J.; Ortega García, J.A.; Soldin, O.P.; Navarro Camba, E.A.; Garcia Castell, J.; Fuster Soler, J.L.
Efectos en la salud pediátrica de la radiación electromagnética de frecuencias extremadamente bajas.
Rev. Española Pediatr. 2010,66, 151–161.
26.
McColl, N.; Auvinen, A.; Kesminiene, A.; Espina, C.; Erdmann, F.; de Vries, E.; Greinert, R.; Harrison, J.;
Schüz, J. European Code against Cancer 4th Edition: Ionising and non-ionising radiation and cáncer.
Cancer Epidemiol. 2015,39, S93–S100. [CrossRef] [PubMed]
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2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
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