Abstract
An investigation studying the effects of electromagnetic field (EMF) shielding, storage duration, and packaging
shape on the quality of natural mineral drinking water has been completed. Eight polymethylmethacrylate
(PMMA) containers (two each of cylindrical, rectangular, square, and pyramidal shapes) were used to store
natural mineral water for 30 days at ambient room temperature (25°C). One group, comprised of one
container of each shape, was shielded by applying a Faraday shield. The surrounding electromagnetic fields
were measured during the storage period by using a portable transmitter systemelectromagnetic field (TSEMF) instrument. Water samples were collected for analysis at the end of one week, two weeks, and one
month during the storage period. The effects of the containers’ shapes and their associated EMFs on the
physicochemical and microbiological qualities of water were explored by means of electromagnetic (EM)
simulation. The physicochemical parameters of the stored water remained within the permissible guidelines of
the World Health Organization. It was observed that variations in the heterotrophic plate count (HPC) occurred
in water samples stored in both shielded and unshielded containers during the storage period. During the
three phases of the study period, there was a significant difference (p < 0.05) in HPC counts between water
stored in the unshielded pyramidal containers and water stored in the unshielded rectangular, square, and
cylindrical containers. There was no total coliform count detected in water stored in the three trials during the
three phases of the study period. The EM simulation, which was conducted at 2400 MHz for both vertical and
horizontal polarizations, showed that the values for the total specific absorption rate (SAR), a measurement of
the energy absorbed by water, were dependent on the shape of the container. Ranked in order of the effect of
the EMFs on the SAR values, with 1 being highest and 4 lowest, the various package shapes would be listed as
(1) pyramidal, (2) square, (3) rectangular, and (4) cylindrical. It can be concluded that the variations in the
values of SAR induced in water are directly related to the variations in the physicochemical and microbiological
parameters of water.
1. Materials and Methods
1.1. Container Manufacturing
Eight containers (two each of cylindrical, rectangular, square, and pyramidal shapes) were manufactured from
3mm-thick polymethyl methacrylate (PMMA) sheets. Using an advanced CNC laser cutting system, holes of
approximately 3 mm in diameter were made in each of these containers to allow for easy placement of water
samples. A square base of 242.362 mm was used with a height of 155.10 mm for manufacturing the pyramidal
container (Fig. 2A). The volume of water in the pyramidal container was calculated by using the dimensions in
Table 1 to solve formula (1). The rectangular, square, and cylindrical containers were manufactured with the
same volume by solving formulas (2), (3), and (4), respectively. The internal dimensions of the four containers
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are shown in Table 1. The internal surface of the containers was isolated by three internal sachets with
0.02mm thickness made of high-density polyethylene (HDPE) layers for each of the containers.
1.2. Electromagnetic shielding
It is well known that electromagnetic fields (EMFs), upon entering conducting regions, decay exponentially
with a characteristic distance (Ilott et al., 2014). A Faraday shield was made using 3mm-thick aluminum sheets
to shield the four containers in one group to minimize the water’s exposure to environmentally abundant
EMFs. The skin depth equation (5) was used to calculate the thickness of aluminum sheets to ensure that the
Faraday shield could cover the detection range of the EMF measurement system.
1.3. Storage Conditions
The eight shielded and unshielded containers were placed on a wooden table and stored in a single 4x6m
room at Halal Products Research Institute, University Putra Malaysia at room temperature (22°25°C) for one
month, maintaining a 40cm distance between each container and a 100cm distance from the walls. The square
bases of the rectangular, square, and pyramidal containers were aligned in the same direction. The water
samples were collected from each container at the end of one week, two weeks, and one month during the
storage period. Regardless of the sample collection, the water containers remained constant throughout the
study.
1.4. Electrical Properties Measurement
In order to measure the dielectric permittivity of water, an Agilent PNA-X Microwave Network Analyzer (Model
N5245A) capable of covering the frequency range of 10–50 MHz was used. The system consisted of an Agilent
85070E dielectric probe with an open-ended coaxial probe and related software. All the measurements and
evaluations in this study were conducted at a room temperature of 2225°C and used a frequency in the range
of 300 MHz to 3 GHz. Complete calibration of the system was done before conducting each measurement.
1.5. Electromagnetic Simulation
In this study, CST Studio Suite 2014 EM simulation software (CST; City, State) was used to explore the
relationship between packaging shape and EM fields and their effects on the distribution of electric and
magnetic fields induced in water. The EM simulation was used to calculate the specific absorption rate (SAR) of
the EM fields induced in water in the four containers. Three-dimensional models of the unshielded four
containers 100 percent filled with water were designed according to the dimensions in Table 1. The electrical
properties such as dielectric constant and conductivity of the materials are closely related to their capacitance
and ability to store energy (Castro-Giráldez et al., 2010). Therefore, in order to mimic the experiment, the
measured electrical properties of water were used in the configuration of the CST Studio Suite 2014 software
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before running the simulation. Plane waves with both vertical and horizontal polarizations were used to excite
each of the four containers. The value for EMF strength recorded by a transmitter systemelectromagnetic
field (TS-EMF) measurement device was used as the amplitude of the plane waves. The values for the azimuth
angle (phi) and elevation angle theta (theta) of the incident plane wave mentioned in the study of Abdelsamie
et al. (2014) of the maximum total SAR values induced in the four container models were used in the
configuration of the CST Studio Suite 2014 software to represent the worst exposure scenario. In order to
truncate the computational region, a perfectly matched layer (PML) was used to represent the absorbing
boundary.
1.6. Sampling
Commercial natural mineral water (Giant; City, State) was used during the three trials of the study. The natural
mineral water was sourced from an underground source, according to the manufacturer. The gallon-sized
bottles of Giant water were represented by using 5.5-liter polyethylene terephthalate (PET) plastic containers
mixed together in an aseptic 25-liter high-density polyethylene (HDPE) water tank (Lifestyle; City, State). The
water in the tank was used to fill eight HDPE sachets, 0.02 mm in thickness, fitted inside each of the
transparent PMMA containers as internal sachets.
2. Results and Discussion
2.1. Electric field strength measurement
The EMF measurements were exported daily from RFEX software (Manufacturer; City, State or Country) during
the three trials of the study. The mean values of the highest values of electric field strength of the three trials
of the study were calculated. The 2400 MHz frequency, which is related to Wi-Fi networks, was selected to
explore the relationship between packaging shape, biological material, and electromagnetic waves. The
highest values of electric field strength at 2400MHz were used in the configuration of the CST Studio Suite
2014 EM simulation software to represent the worst exposure scenario. The maximum values for electric field
strength during the study period are shown in Table 3.
2.2. Material properties
The dielectric properties of natural mineral water at 300MHz3GHz at 25°C were measured. The PMMA
manufacturer (Manufacturer; City, State) was used as a reference for the properties of PMMA, while Cafe
(2005) was used as a reference for the properties of wood, as shown in Table 4.
2.3. Electromagnetic Simulation
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The highest values of electric field strength shown in Table 3 were used as the amplitude of the plane waves in
the configuration of the CST Studio Suite 2014 EM simulation software to represent the worst exposure
scenario. Plane wave excitation was used to excite the surfaces of the pyramidal, rectangular, cylindrical, and
square container models from only one side. According to Abdelsamie et al. (2014), the elevation angles
caused a significant effect on the values of the electric and magnetic fields and the total SAR induced in water
stored in the four container models compared to the azimuth angles. Therefore, the azimuth angle was set to
0°, while the elevation angle (θ) ranged from 0°100° with a step width of 20°. The θ angle of the highest value
for maximum total SAR induced in water in the four container models was used to caculate the maximum
point SAR in water in the four containers.
The maximum values of total SAR (the maximum point SAR induced in water in the pyramidal, cylindrical,
rectangular, and square models for vertical and horizontal polarizations) are shown in Figures 68 and
summarized in Table 7. The results showed significant variations in the maximum total SAR values induced in
water in the four container models for vertical and horizontal polarization, as shown in Figures 3ab.
The results indicated that the total SAR values induced in water in the pyramidal container model were the
highest at theta angles 0°, 20°, 60°, 80° and 100° for vertical and horizontal polarizations, followed by the
square, rectangular, and cylindrical container models. The highest values for maximum total SAR were
recorded at theta 100° for both the vertical and horizontal polarizations. The highest values for maximum total
SAR for the square, rectangular, and cylindrical models were recorded at 100°, 40°, and 40°, respectively, for
vertical polarization and 0°, 0°, and 20°, respectively, for horizontal polarization. The values for maximum point
SAR induced in water in the pyramidal, rectangular, square, and cylindrical models at 2400 MHz for vertical
and horizontal polarizations in different cross sections are shown in Figures 1619 and summarized in Table 7.
The maximum point SAR induced in water in the pyramidal container model was shown to be the highest for
both vertical and horizontal polarizations, followed by the rectangular, square, and cylindrical models for
vertical polarization and the square, rectangular, and cylindrical models for horizontal polarization.
The results optained from the EM simulation showed that while the thickness of the PMMA; the material
properties of PMMA, wood, and water; and the volume of water are identical in all container models, the
variations in values and the distribution of total and maximum point SAR between all container models are
directly related to the differences in the packaging shape and dimensions.
2.4. Physicochemical Quality of the Stored Water
The pre-storage mean value for the pH value for the three trials of water stored in the shielded and unshielded
containers was found to be (M = 7.750, SD = 0.0500) and reached (M = 7.733, SD = 0.1155) and (M = 7.600, SD
= 0.0000) in EM shielded and unshielded groups at the end of the study period, respectively. The study
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revealed a significant difference in pH value (p < 0.05) between water stored in the unshielded pyramidal
container and water stored in the unshielded rectangular, square, and cylindrical containers in the three
phases of the study period, as shown in Table 1. It was observed that the mean value for the pH of all water
samples decreased during the three phases of the storage period in the unshielded containers. There was no
significant difference in pH value (p < 0.05) between water stored in the shielded pyramidal container and
water stored in the shielded rectangular, square, and cylindrical containers in the first and third phases of the
study period, as shown in Table 1. The pH level of water significantly influences the aesthetic quality of
drinking water (World Health Organization [WHO], 1996). The pH level of the medium is also one of the main
factors that determine the diversity and growth of bacterial colonies in stored water. In fact, some
microorganisms produce acidic or basic metabolic wastes that help them to regulate the pH level of their
habitat and frequently change the pH level of water (Prescott et al., 1999).
The pre-storage mean value for the total dissolved solids (TDS) concentration of the three trials of water
stored in the shielded and unshielded containers was found to be (M = 74.00, SD = 1.000) Mg/L and reached
(M = 71.67, SD = 0.577) and (M = 68.00, SD = 0.000) Mg/L at the end of the study period for the shielded and
unshielded groups, respectively. The study showed no significatnt deference in TDS concentration (p < 0.05)
between water stored in the unshielded pyramidal container and water stored in the unshielded rectangular,
square, and cylindrical containers in the first phases of the study period, as shown in Table 3. There was a
significant difference in TDS concentration (p < 0.05) between water in the unshielded pyramidal container
and water in the unshielded square container in the second phase, and between water stored in the pyramidal
container and water stored in square and cylindrical containers in the third phase of the study period. It was
observed that the mean value for TDS concentration of all water samples decreased during the three phases of
the storage period in the shielded and unshielded containers. Water stored in the unshielded pyramidal
container showed the lowest mean value for TDS concentration in the three phases of study.
The pre-storage mean value for hardness of the three trials of water stored in the shielded and unshielded
containers was found to be (M = 64.00, SD = 1.000) Mg/L and reached (M = 62.67, SD = 0.577) and (M = 61.33,
SD = 0.577) Mg/L in the EM shielded and unshielded groups at the end of the study period, respectively. The
study revealed a significant difference in hardness (p < 0.05) between water stored in the unshielded
pyramidal container and water stored in the unshielded rectangular, square, and cylindrical containers in the
second and third phases, and between water in the pyramidal container and water in the cylindrical container
in the first phase of the study period, as shown in Table 3. There was no significant difference in hardness (p <
0.05) between water stored in the shielded pyramidal container and water stored in the shielded rectangular,
square, and cylindrical containers in the first and second phases of the study. The mean value for hardness of
all water samples decreased during the three phases of the storage period in the shielded and unshielded
containers. Water stored in the unshielded pyramidal container showed the lowest mean value for hardness in
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the three phases of study. The hardness of water provides its palatability. The hardness of stored water has
been analyzed according to WHO guidelines (1984). The total hardness of stored water was found to be within
the WHO guidelines, as shown in Tables 5 and 7. The stored water belonged to the moderate soft water
classification of the WHO.
2.5. Bacteriological Quality
The samples taken from all EM shielded and unshielded containers in the first phase showed bacterial regrowth, and subsequent growths tremendously increased during the three phases of the study period. The
highest total heterotrophic bacteria regrowth was detected in water stored in the EM shielded containers
during the three phases of the study period. The mean value for the pre-storage HPC count of the three trials
of water stored inside EM shielded and unshielded container groups was (M = 145.00, SD = 22.913) and
reached the maximum of (M = 202833.33, SD = 3559.302) and (M = 126720.00, SD = 855.044) at the end of the
study period, respectively. The study revealed a significant difference in HPC count (p < 0.05) between water
stored in the unshielded pyramidal container and water stored in the unshielded rectangular, square, and
cylindrical containers in the three phases of the study period.
END OF SAMPLE
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