Anal. Methods Environ. Chem. J. 5 (2) (2022) 76-89
Research Article, Issue 2
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
Determination of mercury values in urine and air of
chloralkali workers by copper nanoparticles functionalized
in carboxylic carbon nanotubes and the effects of mercury
exposure on oxidative stress
Ali Faghihi-Zarandia, Somayyeh Karami-Mohajerib, Morteza Mehdipour Rabouria, Abbas
Mohammadhosseini- Heyrana and Zahed Ahmadi c,*
a Department of Occupational Health, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran
b Pharmaceutics Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran
c Department of Occupational Health Engineering, School of Public Health, Iranshahr University of Medical Sciences, Iranshahr, Iran
ABSTRACT
Mercury exposure can produce toxic organic compounds in the body.
Also, mercury can potentially cause oxidative damage and cellular
disorders. In this study, the determination of mercury values in
urine and air of chloralkali workers based on copper nanoparticles
functionalized in carboxylic carbon nanotubes (CuNPs@CNT-
COOH) were obtained by cold vapor atomic absorption spectrometer
(CV-AAS). The urine samples were determined by magnetic solid-
phase extraction (MSPE) at pH 8.0. By measuring the mercury level
in the air and the urine sample of workers, the level of oxidative
stress (Malondialdehyde (MDA), Superoxide Dismutase (SOD)
and Catalase (Cat)), Interleukin-6 (IL-6), and Tumor Necrosis
Factor α (TNF-α) as the proinammatory cytokines were measured
in the subject group. The results revealed statistically signicant
differences in the mercury level of the urine samples in the case and
control groups (p<0.001). Similarly, the malondialdehyde (MDA)
level was signicantly different between the two research groups
(p<0.001). Catalase concentration was not signicantly different in
the two groups (p=0.059). The LOD and linear range for mercury
determination in urine were achieved at 0.012 µg L−1 and 0.05-7.0
µg L−1, respectively. Workers’ exposure to mercury can signicantly
increase oxidative stress and inammatory cell signaling molecules
such as cytokines.
Keywords:
Mercury,
Air, and Urine,
Magnetic solid-phase extraction,
Oxidative stress,
Copper functionalized carbon
nanotubes,
Cold vapor atomic absorption
spectrometer
ARTICLE INFO:
Received 30 Feb 2022
Revised form 2 May 2022
Accepted 28 May 2022
Available online 30 Jun 2022
*Corresponding Author: Zahed Ahmadi
Email: zahedahmadi68@yahoo.com
https://doi.org/10.24200/amecj.v5.i02.188
------------------------
1. Introduction
In the biogeochemical system of the earth, there
are metallic mercury, organic and non-organic
compounds. Exposure to any of the three can
produce toxic compounds in the body[1]. Heavy
metals are important factors in environmental
pollution and mercury is one of the most toxic and
threatens human health [2]. The greatest effect of
mercury in elemental and organic form in the central
nervous system and the greatest effect of mineral
mercury on the digestive and excretory systems
[3]. Mercury has been extensively investigated
due to its wide range of applications, high toxicity,
long-term ecological effects, aggregation in the
food chain and adverse effects (in exposure to the
low concentration of the liquid metal) [1, 4, 5, 6].
77
Between 40 and 70% of the existing mercury
in the atmosphere is estimated to be induced by
human activities. Direct and indirect exposure of
more than 2 million occupations to this pollutant
is considered a global concern [4, 7, 8]. At work,
exposure to mercury vapor through respiration is
more common [9]. Yet, the alkali form (methyl/
ethyl mercury) is highly soluble in fatty tissues and
also highly volatile. Thus, it can be easily absorbed
in the lungs and then the blood, and is 10 times
as toxic [1]. Occupational mercury exposure can
occur in petrochemical, and chloralkali industries,
uorescent lamps, thermometer manufacturing
companies, glass production and dentistry (tooth
amalgam) [10-12]. Chloralkali processing is a large
industry worldwide in electrochemistry. The main
products are cholera, sodium hydroxide, carbonate
sodium, hydrochloric acid and potash [13]. The
common chloralkali processes include mercury
cell, membrane cell and diaphragm cell. In the
mercury cell process, the anode (carbon electrode)
is hung above the cell and the mercury ows on the
container surface as the cathode [5, 14].When the
electricity is on, the chloride ion dissolved in saline
water turns into the chlorine oxide at the anode side.
Sodium ions are revived as sodium at the cathode
side. Sodium is then solved in mercury and sodium
amalgam (sodium-mercury) is produced. Next, the
amalgam is analyzed. Thus, mercury returns to the
cycle and sodium are turned into sodium hydroxide
[14]. Among the disadvantage of this method are
ecological issues, low efciency in terms of the
voltage used, exposure to mercury and the high
cost [1]. Despite the presence of several metals in
the body such as iron, magnesium, zinc, copper,
cobalt, molybdenum and selenium, the toxicity
of mercury is incomparably high [6]. A body of
research explored the threats to health caused by
exposure to mercury. Instances are disorders in the
nervous system especially the brain, cardiovascular
diseases, metabolic disorders, pulmonary issues,
damage to the immune system, liver, reproduction
system, thyroid, and optical, auditory, tactile and
verbal disorders [4, 7, 12, 15-20]. These studies
showed that the disorders induced by exposure
to mercury produce oxygen radicals in the body.
The cytotoxic effects of mercury (Hg+2) can be
due to the oxidative stress in cells. Hg+2 interacts
with thiols and produces mercaptans. Thus, the
cellular antioxidant buffers based on glutathione
thiol are reduced. Though the exact mechanism of
the production of these radicals is yet unknown,
probably, an increase in reactive oxygen species
(ROS) is the main cause, which results from the
reduced rate of glutathione [21]. Several studies
show that mercury can cause oxidative damage
to multiple organs and systems [21, 22]. Greater
production of ROS can lead to oxidative stress and
may induce dysfunctions and structural damages
such as mutagenesis, carcinogenesis, oxidation, and
deterioration of proteins, carbohydrates, lipids and
DNA [23]. Numerous studies have also identied
a signicant positive relationship between the
dose of mercury exposure in hair samples and
high blood pressure [24]. In the cardiovascular
system, the endothelium functioning is essential
to the maintenance of the blood ow and the
antithrombotic capacity. Vascular endothelial is
highly sensitive to oxidative stress. This stress
can be the main cause of disorders in this tissue in
cardiovascular diseases including hypertension and
atherosclerosis [4, 17]. Measuring changes in the
activity of antioxidant enzymes such as superoxide
dismutase (SOD) and catalase (CAT) is typically
done to act as a biological index in examining
cellular oxidant damages [4, 25, 26]. In cells, SOD
takes charge of analyzing superoxide anions (O2)
into oxygen and hydrogen peroxide (H2O2). Catalase
is in charge of analyzing H2O2 in water and oxygen
[26]. Today, measuring the level of cytokines or low-
weight glycoproteins is another index for cellular
disorders. These hormones interlink cells and the
inner body environment especially the immune
and inammatory systems [21]. Striking a balance
between the two groups (i.e., the proinammatory
and anti-inammatory cytokine groups) is key to
human hemostasis. Measuring proinammatory
cytokines is signicant, for example, interleukin
6 (IL-6) and the tumor necrosis factor alpha (TNF
alpha), both known as major biological indices in
Oxidative stress of mercury and Determination by Nanotechnology Ali Faghihi-Zarandi et al
78
diagnosing cellular damage [27, 28]. The present
research aimed to explore the effects of exposure to
mercury on oxidative stress and proinammatory
cytokines in the body of workers in the chloralkali
industry. In-addition the mercury values were
determined in air ( NIOSH 6009) and human urine
samples based on CuNPs@CNT-COOH by MSPE
procedure at pH 8.5.
2. Materials and Methods
2.1. Instrumental and reagents
A cold vapor atomic absorption spectrometer
(AAS) was used to determination of mercury in
water samples (CV-AAS, HG-3000, GBC, Aus).
The background correction (D2 lamp) the hollow
cathode lamp (HCL, Hg), SnCl2/NaBH4 reagents
and a reaction loop were used for the generation
of mercury vapor and the mercury concentration
determination by CV-AAS. The standard of
inorganic mercury [Hg 2+, 1000 mg L-1 in 1% nitric
acid) was prepared from Sigma Aldrich (CAS
N: 7487-94-7, Germany). The different standard
solutions of mercury were made by diluting
deionized water (DW, Millipore, USA).
2.2. Design and Sampling
The present cross-sectional research was case-
control in type, and was conducted in 2020 in a
chloralkali factory in Tehran. The participants were
179 in number (84 blue-collar workers and 95 white-
collar workers). Screening of different units showed
that 114 participants were directly exposed to
mercury. These workers were signicantly exposed
to mercury as chlorine was produced by traditional
mercury cell processes. Considering the exposure
criteria, among the 114 workers, 84 were found to
be directly exposed and were, thus, selected as the
case. For the control group, 95 white-collar workers
were recruited. The inclusion criteria were: full-
time work and at least two years’ work experience
in the unit. The exclusion criteria were: consuming
antioxidant supplements (e.g., vitamin E or C) and
drugs containing mercury, having renal diseases,
and being non-smokers yet being unwilling to
participate in the study. According to the inclusion
criteria, the nal sample was selected to include
workers who consumed antioxidant supplements
and drugs (n=7), had less than two years’ work
experience and were non-smokers (n=14). Those
unwilling to participate (n=9) were excluded from
the study. The nal remaining 84 blue-collared
workers were included in the research. Thus, the
sampling can be called a consensus. The control
group consisted of ofce workers who were not
exposed to mercury. All the participants agreed
to participate in the study by signing an informed
letter of consent. A demographic questionnaire was
also lled out by all participants to include their
age, weight, height, work experience, smoking
status and type of work shift. The human urine
samples were collected in 114 participants based
on Helsinki Declaration as revised in 2013.
The information, including names, initials, and
hospital numbers don’t publish in text or any other
document. (https://www.wma.net/policies-post/
wma-declaration-of-helsinkiethical-principles-for-
medical-research-involving- ansubjects/).
2.3. Measurement of mercury level in the air
sample
Occupational mercury exposure was measured by
air samples in the participants’ breathing zoon using
the NIOSH 6009 method. The solid sorbent tubes
with 200 mg Hopcalite in a single section were used
as samplers and were connected by Tygon tubing
to the personal pumps calibrated before and after
sampling. The ow rate was adjusted to 2 L min-1
and the sampling duration was set at 3 hours of a
normal work shift. The sorbent tubes were capped
and packed securely for shipment. The Hopcalite
sorbent and the front glass wool of each sample
were placed in separate 50 volumetric asks and
2.5 mL of HNO3. Then, 2.5 mL of HCl was added
to each volumetric ask. The sorbent was dissolved
and diluted to 50 ml with deionized water. 20 mL
of the sample was transferred to a BOD bottle
containing 80 mL of deionized water. All samples
were analyzed using a cold vapor atomic absorption
(GBC-936, 3000, Australia) at a wavelength of
253.7 nm (Fig. 1). The amount of mercury (C) in
Anal. Methods Environ. Chem. J. 5 (2) (2022) 76-89
79
the sampled air volume (V) was calculated using
the following Equation 1:
𝐶 (𝑚𝑔/𝑚3 ) = 𝑊 (µ𝑔) × 𝑉𝑠 (𝑚𝐿) 𝑉𝑎 ⁄ (𝑚𝐿) −
𝐵 (µ𝑔) 𝑉 (𝐿) (Eq. 1)
W is the amount of mercury in the sample aliquot
from the calibration graph. Vs represents the
original sample volume (50 mL). Va stands for
the aliquot volume (20 mL), and B is the average
amount of mercury in the media blanks.
2.4. Measurement of mercury concentration in
the human urine sample
The most practical and sensitive method of
measuring the level of mercury in the body is the
urine sample. That is because mercury exits the
body primarily in the urine. The concentration of the
metal in urine samples shows the exposure within
the past 2-3 months. In this research, mercury in
the urine samples was extracted based on copper
nanoparticles functionalized in carboxylic carbon
nanotubes (CuNPs@CNT-COOH) by magnetic
solid-phase extraction (MSPE) at pH 8.5 before
being determined by cold vapor atomic absorption
spectrometer (CV-AAS). Urine samples were
collected in the eld using a 100 mL sterile plastic
container before the participants’ work shift. The
samples were sealed and packed in an ice bath. The
mercury in 10 mL of urine samples was extracted
with the COOH group of CuNPs@CNT-COOH
at pH=8.0 and then the solid phase was separated
by an external magnetic accessory in the bottom
of the tube. After back-extraction of mercury
from CuNPs@CNT-COOH in acidic pH and
dilution with DW up to 1 mL, the concentration of
mercury in urine samples was determined by CV-
AAS (GBC-936, HG-3000, Australia), equipped
with a Hg lamp at a wavelength of 253.7 nm. The
extraction of toxic mercury with 25 mg of CuNPs@
CNT-COOH was obtained more than 95% in 10
mL of urine samples by MSPE (Fig.2)..
Fig. 1. Measurement of mercury level in the air sample in the participants’ breathing zoon using
the NIOSH 6009 method.
Oxidative stress of mercury and Determination by Nanotechnology Ali Faghihi-Zarandi et al
80
2.5. Measurement of Oxidative Stress
In the present research, the level of Malondialdehyde
(MDA), Superoxide Dismutase (SOD) and
Catalase (Cat) as the oxidative stress indices and
Interleukin-6 (IL-6) and Tumor Necrosis Factor
α (TNF-α) as the proinammatory cytokines
were measured in the collected samples. Five
milliliters of the venal blood were taken from the
participants in both groups before their work shift.
These samples were transferred into sterile tubes
and were allowed to clot. After tube centrifuging
(1600 × g for 10 minutes), the serum samples were
separated and stored at -50 °C before analysis. The
oxidative stress and proinammatory cytokines
were measured using Hangzhou Eastbiopharm kits
(Hangzhou, China) by Double Antibody Sandwich
(DAS) ELISA. The mean value of three repetitions
for each sample was reported.
2.6. Statistical Analysis
Descriptive statistics were used including frequency
(percentage) and median (inter-quartile range)
to summarize demographic variables, oxidative
stress indices and proinammatory cytokines.
The normality and the equality of variances were
analyzed by the Kolmogorov Smirnov test and
the Levene’s test. Demographic variables were
compared in the exposed and unexposed groups
via the chi-square test. To compare the median of
oxidative stress indices, proinammatory cytokines
and the level of mercury in urine samples (urine Hg)
in two groups, the Mann Whitney U-test was run.
Predictors of oxidative stress and proinammatory
cytokines were tested using multiple linear
regression (backward). Variables with more than
two categories entered the regression model after
dummy coding. The variables that did not meet the
normality assumption were normalized according
to the method recommended by Templeton (2011)
before entering the nal model [29]. All statistical
tests were run in SPSS v25 (IBM SPSS, Chicago,
IL) at the signicance level of < 0.05.
3. Results and discussion
3.1. Optimization and validation of mercury
analysis
By the MSPE procedure, the extraction of mercury
in urine samples was achieved by CuNPs@
CNT-COOH nanoparticles. The various mercury
concentration between 0.05–7.0 µg L−1 were used
for the optimization of parameters. The mercury
was extracted and separated in urine samples based
on the COOH groups of CuNPs@CNT-COOH
adsorbent at optimized conditions. The effective
parameters such as the pH, amount of CuNPs@
CNT-COOH adsorbent, the eluents, and the sample
volume were studied.
Fig.2. Measurement of mercury concentration in the human urine sample based
on CuNPs@CNT-COOH by MSPE procedure at pH 8.5
Anal. Methods Environ. Chem. J. 5 (2) (2022) 76-89
81
3.1.1.pH effect
For efcient extraction of mercury in urine samples,
the pH sample must be optimized. So, the different
values between 2 and 11 were studied. The pH is
the critical parameter that was affected by efcient
extraction and absorption capacity by the CuNPs@
CNT-COOH adsorbent. Therefore, the various pH
was selected for Hg(II) extraction in urine samples
using a buffer solution. The results showed that the
high recovery based on the CuNPs@CNT-COOH
adsorbent for mercury extraction was obtained at a
pH of 7.5-8.5. So, the efcient mercury extraction was
obtained at pH 8.0 and the recovery was decreased at
8.5 < pH < 7.0. So, the pH of 8.0 was used as optimized
pH in this study (Fig. 3). The extraction mechanism
occurred based on COOH groups of CuNPs@CNT-
COOH adsorbent as an excellent leaving group
(Hg2+ [:COOH-R])
with the positively charged mercury at pH 8.
At lower pH the COOH groups have positively
charged (+). So, the electrostatic repulsion occurred
between Hg2+ and +COOH groups. In addition, at
more than pH 8.5, the mercury ions participated as
Hg(OH)2.
3.1.2.Optimized CuNPs@CNT-COOH amount
For maximum extraction of mercury in water
samples, the amount of the CuNPs@CNT-
COOH adsorbent must be optimized in mercury
concentration between 0.05–7.0 µg L−1. So, the
various amounts of the CuNPs@CNT-COOH
between 5-40 mg were used for Hg(II) extraction
in urine samples by the MSPE procedure. The
efcient extraction was obtained at more than 20
mg of the CuNPs@CNT-COOH adsorbent for the
extraction of mercury by the proposed procedure.
Therefore, 25 mg of the CuNPs@CNT-COOH was
used for further work at pH=8 (Fig. 4).
Fig. 3. The effect of pH on mercury extraction in urine samples based on CuNPs@CNT-COOH
by MSPE procedure at pH 8.5
Oxidative stress of mercury and Determination by Nanotechnology Ali Faghihi-Zarandi et al
82
3.1.3.Elution process, shaking time and Sample
volume
After extraction of mercury by CuNPs@CNT-
COOH adsorbent, the mercury loaded on the
CuNPs@CNT-COOH must be released from
COOH groups by changing pH. Therefore, the
different eluents such as, HCl, HNO3, and H2SO4,
were used for the back-extraction of mercury
(Hg2+) from the CuNPs@CNT-COOH adsorbent.
The mercury loaded on the CuNPs@CNT-COOH
adsorbent was easily determined by the CV-AAS
after back extraction with inorganic acid at low
pH. In this study, the different eluents (HCl, HNO3,
H2SO4) based on volumes and concentrations were
used for back extraction of Hg(II) in urine samples.
The results showed us that the Hg(II) ions were
back-extracted from the CuNPs@CNT-COOH
adsorbent by the nitric acid solution (0.3 mol L-1; 0.5
mL). Also, the shaking time is the main parameter
for the extraction of mercury in urine samples. So,
the different time was studied from 1 to 10 minute
for mercury extraction at pH 8. The maximum
extraction was obtained in more than 4 min. So, 5
minutes was used as the optimum shaking time. In
addition, the effect of sample volume for mercury
extraction was studied at pH=8. The results showed
us that the mercury can be extracted in 12 mL at
the optimized conditions. So, the 10 mL of urine
samples were selected as the optimum volume for
mercury extraction for further works.
Fig. 4. The effect of amount of adsorbent on mercury extraction in urine samples based
on CuNPs@CNT-COOH by MSPE procedure at pH 8.5
Anal. Methods Environ. Chem. J. 5 (2) (2022) 76-89
83
3.2. Comparing exposed and unexposed groups
Table 1 summarizes the two research groups’
demographic information. More than half of the
participants in both groups had less than 10 years
of work experience. Most of the participants had a
normal BMI. There was no statistically signicant
difference between demographic variables in the
exposed and unexposed groups. The median (inter-
quartile range) of mercury concentration in air
and urine samples, oxidative stress indices and
proinammatory cytokines are shown in Table 2.
The level of mercury in the urine samples of the
exposed group was signicantly different from the
unexposed group (p<.001). In addition, the lipid
peroxidation products were measured as MDA
and showed to diverge signicantly between the
two groups (p≤.001). The results also showed that
the level of all oxidative stress indices (except
for catalase) and inammatory cytokines were
signicantly higher in the exposed group than the
unexposed. Catalase concentration did not account
for any statistically signicant difference between
the two groups (p=.059). The concentration of
mercury in urine samples was the most signicant
Table 1. Demographic variables of the exposed group (n=84) vs. unexposed group (n=95)
Variable Classication Frequency (%) P-value*
Exposed group Unexposed group
Age
<30 33 (39.3) 43 (45.3)
0.67430-40 37 (44) 36 (37.9)
>40 14 (16.7) 16 (16.8)
Experience ≤10 47 (56) 56 (58.9) 0.686
>10 37 (44) 39 (41.1)
BMI
Underweighted 4 (4.7) 7 (7.4)
0.392Normal 75 (89.3) 78 (82.1)
Obesity 5 (6) 10 (10.5)
Shift work Yes 23 (27.4) 20 (21.1) 0.323
No 61 (72.6) 75 (78.9)
* Chi-square
Table 2. Mercury level in air and urine samples, oxidative stress
and proinammatory cytokines in the exposed vs. unexposed groups
Variables
Median (inter-quartile range)
P-value*
Exposed group
(n=84)
Unexposed group
(n=95)
Air Hg () 18.49 (13.75) - -
Urine Hg (µg L-1) 15.44 (19.85) 4.62 (3.64) <0.001
Malondialdehyde (µmol L-1) 6.65 (4.88) 2.41 (3.06) <0.001
Superoxide Dismutase (U L-1) 312.97 (244.67) 242.82 (144.35) 0.004
Catalase (U L-1) 1.16 (1.68) 1.31 (0.32) 0.059
Interleukin 6 (pg mL-1) 1.79 (1.41) 0.51 (0.62) <0.001
Tumor Necrosis Factor α (pg mL-1) 8.13 (7.88) 4.77 (3.89) <0.001
* Mann Whitney U
Oxidative stress of mercury and Determination by Nanotechnology Ali Faghihi-Zarandi et al
84
predictor of oxidative stress and proinammatory
cytokines based on a multiple backward linear
regression. As the results showed, an increase
for 1 mg of mercury in the urine was followed
by signicant changes in the oxidative stress
and proinammatory cytokines. The regression
analysis results (Table 3) show that a 1 mg L-1 of
increase in urine mercury was followed by about
a 12% of the increase in MDA level. Also, any
1 mg of increase in urine mercury showed to be
followed by a four-fold increase in SOD. Similarly,
any 1 mg of increase in urine mercury was found to
predict a 14% of the increase in TNF-a. However,
the same amount of increase in mercury showed to
a predict 9% and 2% of increase in CAT and IL-
6, respectively. These were the lowest levels of
predicted variance in the present ndings.
3.3. Discussion
The overall ndings showed that among the
chloralkal unit workers, the levels of oxidative
stress and proinammatory cytokines were higher
in the exposed group than the control. All the
variables except for the catalase were signicantly
different between the two groups (Fig.5). These
ndings point to the increase in oxidative stress
and body immune responses in this population.
The maximum permitted level of mercury in
blood and urine is 3 and 4-5 mg L-1, respectively
[30]. The present ndings, however, showed that
the mercury concentration was more than these
limits in the sampled population. Similarly, in
their research, Neghab et al. found a higher (than
the standard level) concentration of mercury in
the exposed group, and they found a statistically
signicant difference between the two groups with
this regard. This study not only measured and
compared the mercury concentration but also the
oxidative stress and proinammatory cytokines
[22]. Different mechanisms have been suggested
to explain the biological toxicity of mercury,
such as the oxidative stress and inammatory
mechanisms. Yet, the precise mechanism of
producing ROS and inammatory mediators by
mercury is unknown. Oxidative stress is a primary
lead-induced mechanism. The present ndings
attested to the capability of mercury to generate
free oxidative species through increasing the level
of LPO. MDA is a main product of non-oxidized
unsaturated fatty acids. An increase in MDA
content is a key indicator of LPO [31]. Mahboub et
al. investigated this issue and showed that HgCl2
manages to increase the MDA level in tissues [32].
In this research, the MDA level was signicantly
different between the exposed and non-exposed
groups. Moreover, the urine mercury level was
a strong predictor of the MDA level. In another
study, Hasan et al. showed that the MDA level was
signicantly increased along with the increased
mercury concentration [33].
Table 3. Predictors of oxidative stress and proinammatory cytokines in the exposed group
Variable β95% CI P-value
Independent Dependent Lower Upper
MDA Age Group (>30 vs 30-40) 1.33 0.066 2.61 0.039
Urine Hg 0.123 0.069 0.178 <0.001
SOD
BMI Group
(Underweight vs Normal) 182.22 54.21 310.23 0.006
Urine Hg 4.22 1.51 6.92 0.003
Cat Shift Work (No vs Yes) -1.39 -2.72 -0.057 0.041
Urine Hg 0.094 0.041 0.146 0.001
IL-6 Urine Hg 0.028 0.12 0.45 0.001
TNF-α Urine Hg 0.145 0.056 0.233 0.002
Anal. Methods Environ. Chem. J. 5 (2) (2022) 76-89
85
Lipid peroxidation is a chemical mechanism that can
disrupt the structure and functioning of biological
membranes by the free radicals attacking the lipids.
The higher peroxidation rate of serum lipids in
exposed workers to mercury is indicative of serious
oxidative damages [31]. As a metallic compound,
mercury reacts to thiols (SH-) and leads to chelate
antioxidant proteins such as glutathione. Finally,
reducing the antioxidant capacity of the tissues
induces oxidative stress [34] the overproduction
of ROS by mercury indicates its capability of
making mitochondrial changes by blocking the
mitochondrial permeability transition pore [35].
The Overabundance of ROS induced by mercury
correlates to the incidence of neurodegenerative
diseases such as amyotrophic lateral sclerosis,
Parkinson’s, or Alzheimer’s. The recent research
showed that within the past decades, the toxic effects
of mercury have been correlated, probably, with the
central nervous system [36]. Several studies, similar
to the present research, showed that exposure to
lower concentrations of mercury, rstly, induces
oxidative stress and increases the number of free
oxygen radicals compared to the existing serum
antioxidant mechanisms [6, 37]. An increased
number of free oxygen species can be one reason
for the analysis of proteins, lipid peroxidation, and
cellular damage or mortality [23]. As also raised
by Neghab et al., mercury can damage cellular
membrane through lipid peroxidation and nally
disturbs the balance of synthesis and, consequently,
leads to enzymatic protein deterioration [22]. The
present research also revealed that the level of
inammatory mediators, (e.g. IL-6 and TNF alpha)
was signicantly higher in the exposed group
of workers than the non-exposed. This nding is
consistent with Gardner et al.’s epidemiologic
investigation of the mercury level among 94
workers exposed to mercury at work. Investigating
the level of proinammatory cytokines (e.g. TNF-
alpha and IL-6) in the mercury exposed workers
in gold mines showed that the urine mercury level
correlates with an increase in IL-1B, TNF-a, and
IFN-Y in the gold miner population. Exposure to
mercury in these mines can disrupt the immune
body and inammatory systems [40]. Furthermore,
the research ndings of animal models showed a
signicant correlation between the mercury level
and proinammatory cytokines such as TNF-a, IL-
6, and IFN-y [37-39].
Fig.5. Flow diagram effects of mercury exposure on oxidative stress and proinammatory cytokines
Oxidative stress of mercury and Determination by Nanotechnology Ali Faghihi-Zarandi et al
86
Several empirical and epidemiologic studies showed
that mercury level was correlated with different
cytokine proles. Results of the experimental
study of PBMC Gardner et al. showed that in the
presence of LPS, the antigenic stimulus of non-
organic mercury can increase the propagation of
proinammatory cytokines IL-1B and TNF-a.
Simultaneously, it reduces the propagation of
anti-inammatory cytokines, IL-1Ra, and IL-10
[40]. Yet, in another study, Monastero et al. aimed
to explore the correlation between exposure to a
low mercury concentration, immunologic indices,
and several cytokines such as TNF-a, IL-10, IL-4,
IL-1B, IL-1ra, IFN-y, and IL-17. Results showed
that the serum mercury level and the antinuclear
antibody (ANA) or cytokine did not correlate in
seafood consumers in the U.S. The Association
between exposure to low concentrations of mercury
and immunologic indices is unknown. Monastero
et al. found a high mercury concentration in urine
and blood samples of subjects exposed to a low
level of mercury. However, in this research, the
concentration of mercury in workers’ blood and
urine exceeded the recommended level [41, 42].
4. Conclusion
The present ndings revealed that workers exposed
to mercury have signicantly more oxidative and
inammatory mediator damages. These observations
highlight the essentiality of preventive measures at
the workplace and checking the state of pollutants
at work. Many studies conrmed that an increase in
oxidative stress and inammatory factors is followed
by a higher risk of afiction with other diseases. The
mercury in urine samples was determined based
on CuNPs@CNT-COOH adsorbent by the MSPE
procedure coupled to CV AAS. The absorption
capacity of CuNPs@CNT-COOH for mercury was
achieved at 167.5 mg g-1. Also, the mercury in the air
was obtained by the NIOSH method. The recovery
and RSD for mercury extraction in urine were more
than 96% and 1.65%, respectively.
5. Conict of Interest
The authors have declared no conict of interest.
6. Acknowledgment
The work supported by the Kerman University of
Medical Sciences is based on a number of projects
PN: 401000242, for mercury determination in
air and human urine samples by supervisors.
The ethical code obtained by Kerman University of
Medical Sciences (E.C.:IR.KMU.REC. 1400.144).
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