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European Journal of Applied Sciences – Vol. 10, No. 1
Publication Date: February 25, 2022
DOI:10.14738/aivp.101.11613. Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment
of Heavy Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-
462.
Services for Science and Education – United Kingdom
Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar,
Nigeria
I. O. OYO-ITA
Organic Chemistry and Food Science Research Group
Department of Pure & Applied Chemistry, University of Calabar, Nigeria
P. Y. NKOM
Organic Chemistry and Food Science Research Group
Department of Pure & Applied Chemistry
University of Calabar, Nigeria
Department of Chemical Sciences, Cross River
University of Science and Technology, Nigeria
F. E. UMO
Organic Chemistry and Food Science Research Group
Department of Pure & Applied Chemistry
University of Calabar, Nigeria
E. ETON
Department of Science Education
University of Calabar, Calabar-Nigeria
H. A. NEJI
Department of Science Education
University of Calabar, Calabar-Nigeria
O. E. OYO-ITA
Organic Chemistry and Food Science Research Group
Department of Pure & Applied Chemistry, University of Calabar, Nigeria
Department of Chemical Sciences, Cross River
University of Science and Technology, Nigeria
ABSTRACT
Selected heavy metals accumulation and health risk assessment were investigated
in the tissues of the widely consumed fish (Ethmalosa Fimbriata, Clarias Gariepenus,
and Tilapia Guineensis) and shrimp (Macrobrachium Felicinum) species in Calabar.
The mean concentrations of Cr, Pb, and Ni were slightly higher than the standard
levels and Hg was below detection level for all samples. Zn, Cd and Cu contents of
fish and shrimp were below the maximum guideline proposed by the US Food and
Drug Administration. The average estimated weekly intake was significantly below
the provisional tolerable intake based on the FAO and WHO standards for all
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
studied metals. The combined Total hazard quotient (THQ) of the studied heavy
metals were above 1 that is 7.48 for the fish and 7.0 for the shrimp and was highest
for Cr suggesting a possible carcinogenic risk to consumers of this product via Cr.
The carcinogenic risk of Pb in both species was within the acceptable range of 10-4 -
10-6 mg/kg/day. Results of this study reveal an almost safe level of Zn, Cd, Cu, and
Hg contents in the fish and shrimp consumed by Crossrivarians but recommend to
appropriate authorities to stop the sources and use of Cr, Pb, and Ni.
Keywords: Consumption, Health risk assessment, Heavy metals, Fish, Shrimp, Calabar.
INTRODUCTION
Increasing rates of consumption of Bonga fish (Ethmalosa Fimbriata), Catfish (Clarias
Gariepenus), Tilapia fish (Tilapia Guineensis) and shrimps (Macrobrachium Felicinum) as
popular delicacy in Calabar has raised worries about the safety of health of consumers in the
face of perceived rising input of heavy metals in aquatic habitat associated with increasing
urbanization. This is as a result of their tendency to absorb toxic pollutants from the
surrounding aquatic environment, depending on a variety of factors like; the characteristics of
the species under consideration, the exposure period, concentration of the elements,
temperature, salinity, pH, seasonal changes etc.,(Kwaansa-Ansah et al., 2018). Apart from being
part of the local delicacy, these commercially available sea foods are widely consumed because
of their high protein, low saturated fat and appreciable omega-3 fatty acids contents that
promote good health.
Heavy metals are well known environmental pollutants due to their toxicity, persistence in the
environment and bio accumulative nature. Their natural sources include volcanic eruptions and
weathering of metal-bearing rocks, while their anthropogenic sources include combustion of
fossil fuels, various industrial and agricultural activities etc (Essien et al., 2009). Accumulation
of potentially toxic heavy metals in sea foods and biota causes a potential health threat to their
consumers including humans. The accumulation of heavy metals in tissues of fish and shrimp
may cause actual adverse health effects via their intake and various species of fish and shrimp
are normally used as bio indicators to study heavy metals accumulation in aquatic
environments, in addition to assessing risks caused by anthropogenic activities (Kwaansa- Ansah et al., 2018).
Government and Communities have been compelled to address the issues of Global changes,
which includes growth in human population, temperature, sea level rise and contaminants
locally and globally. The formulation of policy and regulations occurs at more local scales and
requires information and data to support the regulations (Joanna et al., 2019). This increase in
human population has caused more fish and shrimps to be consumed even as more
contaminants like heavy metals from urbanization and industrialization could threaten their
suitability for human consumption.
In Cross River State, a number of studies have reported Heavy metals in sea foods and Cross
River estuary (Essien et al., 2009; Obot et. al., 2016 etc.). However, accrual of heavy metals in
muscle tissues of commercially significant seafood and their exposure level to consumers in
Calabar metropolis is yet to be reported and the general people and authorities are not mindful
of the health implication. Calabar is the capital of Cross River State, Nigeria. It was originally
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
Services for Science and Education – United Kingdom
named Akwa Akpa, in the Efik language and is adjacent to the Calabar and Great Kwa rivers and
creeks of the Cross River from its inland delta. Calabar is often described as the tourism capital
of Nigeria, especially due to several initiatives implemented during the administration of
Donald Duke (1999–2007), which made the city the cleanest and most environmentally friendly
city in Nigeria (Achum, 2017). It has an area of 406 square kilometres (157 sq mi) at an
elevation of 32 m (105 ft) with a population of 371,022 as at 2006 census and a density of
910/km2 (2,400/sq m). The Cross River State Annual Christmas Festival held every year
attracts thousands from within and beyond Nigeria. The festival, includes music performance
from both local and international artists. Other annual events include the Calabar Carnival, a
boat regatta, fashion shows, a Christmas Village, traditional dances and the annual Ekpe Festival
(Achum, 2017). Being a tourist destination where fresh fish serve with shrimps is one of the
major cuisine delicacies, there is necessity to constantly monitor the accumulation of heavy
metals in these sea food species. This work therefore seeks to close this gap in knowledge, by
examining the concentration and health risk assessment of selected heavy metals (Cd, Cr, Cu,
Ni, Hg, Pb and Zn) accumulation in Bonga fish (Ethmalosa Fimbriata), Catfish (Clarias
Gariepenus), Tilapia fish (Tilapia Guineensis) and shrimps (Macrobrachium Felicinum) in
Calabar Metroplolis and evaluate the dietary intake as a basic step to assess consumer’s
exposure to heavy metals.
MATERIAL AND METHODS
Collection and analysis of samples
A total of eighty-four (84) freshly caught male and female Ethmalosa Fimbriata (n=36), Clarias
Gariepenus (n=24), Tilapia Guineensis (n=24) and 2400g of Macrobrachium Felicinum were
bought from local shops in four (4) different locations, including; Beach, Lagos Street, Mbukpa
and Watt Markets between the months of April and September, 2021. The species used in this
study was based on their accessibility, popularity among local consumers as well as their
consumption rate during the study period. The samples were placed in clean plastic bags (each
species in a separate bag), stored on an ice chest to avoid deterioration and transported to the
Department of Food Science and Technology, Faculty of Agricultural Science, University of
Calabar, Nigeria for taxonomic identification. Total length was measured from the top most part
of the mouth to the tip of the caudal fine and standard length were measured from the top most
part of the mouth to the tip of hypural bone, using a meter rule. Fresh weights were measured
using an electronic weighing balance after removing water and other substances. Samples were
washed with distilled water and kept in a refrigerator prior to digestion and chemical analysis.
Biological information and trophic level characteristics of the studied fish and shrimp species
are shown in Table 1.
Determination of heavy metals
The samples were washed with distilled water and a total of 20 g each of fish and shrimp tissues
was removed and dried at 105 °C for 24 h and then transferred to a desiccator until it reached
a constant weight. Then, 0.5 g of each sample was powdered and transferred to a beaker
containing 5 mL of nitric acid. The mixture was heated up to 140 °C to obtain a clear solution.
The solution was then filtered and diluted to 50 mL and used for metal analysis. The
concentrations of the selected heavy metals Cd, Cr, Cu, Zn, Hg, Ni, and Pb in the digested
solutions were measured using an atomic absorption spectrophotometer (Varian AA-7000).
Standard heavy metal solutions (1000 mg/L) were used to plot the calibration curves after
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
appropriate dilutions. Limit of detection was <0.001 mg/l and levels of heavy metals were
expressed as mg/kg wet weight (Miri et al., 2017).
Intake rate limits
Estimated weekly and daily intakes
The estimated daily intake (EDI) was evaluated as optimized by Miri et al., 2017 thus:
EDI = �! ∗ �" ∗ �#$ ∗ �! ∗ �%
�&' ∗ �&
∗ 10() ... ... ... ... .... (1)
where ED, EF, CF, WAB, FIR, CM and TA are the exposure duration (60 years), exposure frequency
(365 days/year), conversion factor (0.208) to convert dry weight of fish/shrimp to wet weight,
average body weight for adult (65 kg), ingestion rate (25.2 g/day), heavy metal concentrations
in muscle tissues of fish/shrimp and average exposure time (EF *ED), respectively (Miri et al.,
2017).
The estimated weekly intake (EWI) was evaluated following procedures by USEPA (2011);
EWI = �% ∗ �$
�&'
... ... ... ... .... (2)
where CR represent the fish/shrimp consumption rates (ca. 0.160 kg of fish/shrimp per week)
(FAO, 2016).
The percentage of provisional tolerable weekly intake (%PTWI)
The %PTWI was evaluated for each heavy metal using;
% PTW1 = ���
���� ... ... ... ... ... ... ... ... ... ... ... (3)
The PTWI (mg/kg bw/week) guidelines were employ in this study (Cd=0.007, Cr=23.3, Cu=3.5,
Ni=0.365, Pb=0.025 and Zn = 7.0 in mgkg-1 (JECFA, 2003).
Daily intake limit
Daily consumption rate limit (CRlim) of the studied fish and shrimp species was evaluated for
carcinogenic effects of contaminants using:
��*+, = ARL ∗ �&'
CSF ∗ �%
... ... ... ... ... ... . (4)
where ARL and CSF are the maximum acceptable lifetime risk level (10-5) and cancer slope
factor, respectively (Yu et al., 2014). The cancer slope factor value of Pb according to the
Integrated Risk Information System is 0.0085 mg/kg day-1 (USEPA, 2011).
The maximum acceptable daily intake of fish and shrimp was also calculated for non- carcinogenic risk of heavy metals contaminant using:
��*+, = R�� ∗ �&'
�%
... ... ... ... ... ... ... . . (5)
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
Services for Science and Education – United Kingdom
where RfD is the oral reference dose. The RfD values of Cd=0.001, Cr=0.003, Cu=0.04, Ni=0.02,
Pb=0.035 and Zn = 0.3, in mg/kg-day-1 respectively (USEPA, 2011). The maximum allowable
intake rate of fish and shrimp contaminated with heavy was determined as published in Shakeri
et al., 2015:
��,, = ��*+, ∗ �-.
�� ... ... ... ... ... ... ... . . (6)
where MS, Tap, and CRmm are the meal size (0.227 kg fish or shrimps/meals), average time
period (30.44 day/month), and maximum allowable intake rate, respectively.
Metal pollution index (MPI)
The MPI was utilized to calculate the accretion of total heavy metals, as shown in Kwaansa- Ansah et al., 2018;
MPI = (�/ ∗ �0 ∗ �) ... ... . �1)//1 ... ... ... ... ... ... (7�)
Multi-element contamination (MEC)
MEC provides a measure to assess contamination based on the content of heavy metals in
studied samples with the PTWI limits Adamu and Nganje (2010). MEC values above 1.0 signify
an anthropogenic impact on heavy metal concentration in studied samples. MEC was calculated
based on the following formula:
MEC =
�/
�/
+ �0
�0
+ �)
�)
... ... .
�1
�1
n ... ... ... ... .... (7�)
where C—content of heavy metal, T—provisional tolerable levels and n—the number of heavy
metals.
Health risks assessments
Target hazard quotient (THQ)
Non-carcinogenic risks were examined based on THQ determination and the hazard index (HI)
evaluated by adding all the target hazard quotient values respectively as follows;
THQ = �! ∗ �" ∗ �#$ ∗ �! ∗ �%
�&' ∗ �& ∗ ��� ∗ 10() ... ... ... ... .... (8�)
�� = ∑��� ... ... ... ... ... ... ... . (8�)
If the THQ or HI is below one, it implies no threat to health, THQ or HI above 1, indicate a higher
risk associated with fish/shrimp intake (USEPA, 2011).
Cancer risks (CR)
The CR over a lifetime of Pb exposure was calculated as reported by Kwaansa-Ansah et al., 2018
thus;
�� = ��� ∗ ��� ... ... ... ... ... ... ... (9)
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
Condition factor (K)
The condition factor which reflects the physiological and health states of marine species was
evaluated following Froese, 2006 procedures as demonstrated below:
K = W
�) ∗ 100 ... ... ... ... .... (10)
Where W and L are the fresh weight (g), and length (cm) of fish/shrimp, respectively. A factor
of 100 was used to bring the coefficient of condition close to unity. In general, higher K value
reveals fatter or thicker species.
Statistical analysis
The statistical analysis was performed using IBM Statistical Package for Social Sciences (SPSS)
v. 20 software. A normality test was carried out to evaluate whether the data of each samples
were normally distributed. Concentrations of the analyzed Heavy metals were express as
mean±standard deviation and the association between fish size (length and weight) and heavy
metal concentrations among the fish and shrimp species was assessed using Pearson’s
correlation analysis. The cluster and principal component analyses were utilized to attain a
further understanding of heavy metal distributions by evaluating the similarities or
dissimilarities in the different fish and shrimp samples. The principal component analysis was
carried out by Ward’s Method and Varimax normalized rotation was used to extract
components with an eigenvalue greater than one.
RESULTS AND DISCUSSION
Heavy metal concentrations
The concentration of selected heavy metals observed in the tissues of Ethmalosa Fimbriata,
Clarias Gariepenus, Tilapia Guineensis and Macrobrachium Felicinum are presented in Table 2.
Total concentration of heavy metal in mg/kg for the studied species were in the order
Ethmalosa Fimbriata> Clarias Gariepenus> Macrobrachium Felicinum> Tilapia Guineensis and
ranged between 18.38 – 25.90 mg/kg with an overall total of 85.12±9.90 mg/kg. Ethmalosa
Fimbriata being the only member of its genus and dwells particularly where rivers bring large
amount of detritus into the sea has a dissimilar size, age and feeding pattern. This attributes
may explain the highest level observed for Ethmalosa Fimbriata because this metals have
varying accumulations behavior in different species of fish/shrimp and several factors
including feeding behavior, swimming pattern, reproductive cycle, as well as sex, size, and age
can affect their intake (Canli and Atli, 2003).
Heavy metals recorded in the studied fish and shrimp species followed the order of
Cr>Pb>Cu>Ni>Zn>Cd while Hg was below detection levels for all the studied samples (Table 2).
This agrees with the finding that Cr, Pb, and Cu are some of the persistent toxic metals known
in most environmental matrices (Akinrotimi and Edun, 2015). A two-way ANOVA showed that
these metals were not normally distributed (p<0.05; SI1) in the analyzed samples. A low
coefficient of variation (CV) was observed for Cr (16.96%), Pb (12.59%) and Cu (12.35%); (CV
≤ 20%), moderate for Ni (32.32%); (21% <CV ≤ 50%), high variability for Zn (53.49%);
(50%<CV ≤ 100%) and exceeded 100% for Cd (102.31%) Table 2, (Kwaansa-Ansah et al.,
2018). These result revealed that the concentration levels of Cr, Pb, and Cu did not vary
significantly in the studied fish and shrimp samples while that of Ni indicated a non- homogenous levels. Coefficient of variation (CV) greater than 100% as in the case of Cd is an
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indication that the standard deviation exceeded the mean value. The condition factor (K)
conveyed a variable health effect with respect to heavy metal contamination. The K value>1 for
both fish and shrimp samples (7.02 and 2.28 respectively. Table 3.) revealed that all the studied
samples were healthy (Kwaansa-Ansah et al., 2018) and this was higher than the K value in the
range of 1.05–1.89 recorded by Chandra and Jhan (2010).
The mean concentration of Cd ranging from 0.03±0.01 mg/kg in Macrobrachium Felicinum and
Tilapia Guineensis to 0.13±0.11 mg/kg in Clarias Gariepenus, Zn in the range of 0.46±0.02 mg/kg
in Tilapia Guineensis to 1.64±0.02 mg/kg in Ethmalosa Fimbriata and Cu with a minimum value
of 6.25±0.67 mg/kg in Tilapia Guineensis and a maximum of 7.73±0.49 mg/kg in Ethmalosa
Fimbriata were below the level proposed by FAO/WHO (0.50, 100 and 30.0 mg/kg). On the
hand, levels of Cr, Ni and Pb ranging between 5.14±0.79 mg/kg in Tilapia Guineensis to
7.47±0.02 mg/kg in Ethmalosa Fimbriata, 1.12±0.18 mg/kg in Clarias Gariepenus to 2.30±0.12
mg/kg in Ethmalosa Fimbriata and 5.07±0.28 mg/kg in Macrobrachium Felicinum to 6.68±0.05
mg/kg in Ethmalosa Fimbriata respectively were higher than the FAO/WHO permissible values
of 0.15 mg/kg, 0.6 mg/kg and 2.0 mg/kg respectively (FAO, 2016).
Chromium is naturally present in the environment in trace amounts, but industrial use in
rubber and stainless steel manufacturing, chrome plating, dyes for textiles, timber treatment to
protect wood from decay fungi, wood-attacking insects and other uses contaminates aquatic
systems. Antifouling paints used to prevent growth of marine organism on boats contain Pb and
Nickel as important components and they can also be released into the atmosphere by coal- burning power plants and garbage incinerators, Chandra and Jhan (2010). Farombi et al. (2007)
have also reported that Cr, Pb, Ni and Cd are the major heavy metals associated with Nigerian
crude oils. Thus, the high concentration of Cr, Ni and Pb found in the studied fish and shrimp
species from Calabar is suspected because the location of the study is around the local mining,
illegal refineries, timber and paint industries areas where wastes produced are not properly
disposed. This observation corroborates the assertion that marine biota that is of economic
importance as food sources from the sea and coast are also polluted (Farombi et al. 2007).
Therefore, research efforts to monitor pollutants, especially metals contained in food sourced
from sea and coastal areas should be encouraged.
Despite the high population of Watt market, the highest heavy metal load with regard to
sampling sites was reported at Mbukpa market (22.45±2.9 mg/kg; Fig. 1). This probably may
be associated with atmospheric precipitation arising from illegal oil bunkering activities in its
vicinity.
Heavy metal concentrations measured in the studied fish and shrimp species were compared
with earlier studies. The concentration of Pd, Zn, Cd, Ni, and Cu of this study was comparable
with those in the Dhaleshwari River, Fosu Lagoon and Hypermarkets (Ahmed et al., 2009: Akoto
et al., 2014; Alturiqi and Albedair, 2012) and lower than those in Bodo creek, Cross River
Mangrove swamp and Lower Cross River Estuary, Niger Delta, Nigeria. (Abu et al, 2016: Essien
et al., 2008, Obot et al., 2016). This comparison discloses that these metals contaminant in fish
and shrimp from Calabar may not pose serious health issues compared to those that have been
recorded in literature.
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
Consumption rate limits
The daily consumption of the selected heavy metals was assessed based on their concentrations
in the tissues of the investigated fish and shrimp species. The consumption rate limits values
are given in Table 3. The concentration of heavy metals recorded in tissues of the studied
samples were used to evaluate the health risk posed by the intake of fish and shrimp in Calabar.
The estimated daily intake (EDI) was in the trend Cu>Cr>Pb>Ni>Zn>Cd and similar order was
also observed for the weekly intake (EWI). The %PTWI revealed: Pb>Cd>Ni>Cu>Cr>Zn. The
highest EDI values compared with the least PTDI values for all the studied heavy metals
indicated that the intake of the studied fish and shrimp species poses no effect on consumers.
These EDI values were comparable with earlier studies for several fish species sampled from
Chilika lagoon (Parida et al., 2017), Subarnarekha River (Giri and Singh, 2015) and Asafo
market, Ghana (Kwaansa-Ansah et al., 2018).
Metal Pollution Index
Pollution indices are widely considered a useful tool for the comprehensive evaluation of the
degree of contamination. Moreover, they can have great importance in the assessment of food
quality and the forecast of future ecosystem continuity. A rating, reflecting the composite
influence of dissolved heavy metals in the studied species was done by calculating the MPI. The
trend of total concentrations of heavy metal accretions by MPI in the studied species was in the
order: Ethmalosa Fimbriata (2.20)> Clarias Gariepenus (1.75)> Macrobrachium Felicinum
(1.28)> Tilapia Guineensis (1.21) (Table 2) and support that Ethmalosa Fimbriata fish species
accumulated the highest heavy metals than the other fish and shrimp species. This agreed well
with the pattern of heavy metal concentrations and also indicate that the varying accumulations
behavior in different species of fish and shrimp which relied on their feeding habit affected the
MPI values more than the weight factor in this case. The MPIs value of this study was more than
three order of magnitude higher than those reported for Asafo market, Ghana (0.021 – 0.036)
Kwaansa-Ansah et al., 2018 and comparable with the MPIs value of Pikeperch (0.91), Hao et al.,
2013.
Health Risk Assessment
The risk assessment results are given in Table 4. The non-carcinogenic daily intake rate effects
range between 7.66 x 10-4 kg/day for Cr and 4.99 kg/day for Zn in the analyzed fish and between
8.04 x 10-4 kg/day for Cr and 8.78 kg/day for Zn in the studied shrimp species. Also, the
carcinogenic daily consumption rate limit of Pb in the analyzed fish and shrimp species was
3.28 x 10-3 kg/day and 3.77 x 10-3 kg/day respectively. This relatively low values are expected
not to cause any adverse effects on human health. The meal size for non-carcinogenic effect of
the analyzed fish was in the range 0.10 in Cr to 668.77 meals/month in Zn and between 0.11 in
Cr to 1177.88 meals/month in Zn for shrimp. Meals/month of carcinogenic effect of Pb was 0.44
and 0.51 for the fish and shrimp species respectively. THQ was in the trend Cr>Pb>Cu>Cd>
Ni>Zn for the fish and Cr>Pb>Cu>Ni>Cd>Zn for the shrimp and were all less than 1 except for
Cr which recorded the highest value (8.84 and 6.52) for the fish and shrimps respectively. The
combined HI of the studied heavy metals were 7.48 for the fish and 7.0 for the shrimp. These
high values which are far greater than one and in addition to the high THQ value of Cr in both
fish and shrimp samples revealed high bioaccumulation of Cr as it concentration level on the
studied species exceeds the recommended limits. This suggest a possible carcinogenic risk to
consumers of this product via Cr consumption. The combined HI of this study was higher than
those reported in Sistan region, Iran (26.94 x 10-3) Miri et al., 2017 and Asafor Market, Ghana
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(2.61 x 10-3) Kwaansa-Ansah et al., 2018 while similar HI value was reported for wild fishes in
the Southern Sea of Korea and followed the order; Cd>Cr>Zn, Hwang et al. (2017).
The carcinogenic risk factor (CR) of Pb calculated for fish and shrimp consumption in Calabar
was 1.60 x 10-5 and 1.39 x 10-5 mg/kg/day respectively. Generally, CR above 10-4 are regarded
as unacceptable, CR below 10-6 as negligible, and ranging from 10-4 to 10-6 as an acceptable
carcinogenic risk factor (USEPA, 2011). Therefore, the CR value of Pb (1.60 x 10-5 and 1.39 x 10-
5) mg/kg/day was in an acceptable range and was lower compared to CR in the range 1.0 x 10-
3 to 9.01 x 10-3 mg/kg/day calculated for frequently consumed fish species in Bogra District of
Bangladesh (Islam et al., 2016), comparable to CR of 6.75 x 10-5 mg/kg/day in Asafor Market,
Ghana (Kwaansa-Ansah et al., 2018) and higher to CR of 1.57 x 10-7 mg/kg/day via fish intake
in Sistan region (Miri et al., 2017).
Relationship and source of Heavy metals pollution
The association between studied sea food size and heavy metals concentration was checked by
Pearson’s correlation analysis for each fish and shrimp species. Most heavy metals had
significant correlations (0.50< r < 1.0) with the strongest observed for Pb and Zn (r=0.9052,
SI2) with each at p<0.05. The positive correlation between weight and length assent well with
earlier findings by Miri et al., 2017 and may be ascribed to their similar spreading bearing,
natural and man-made activities. Nonetheless, Cd did not show any significant association with
fish and shrimp size for all the studied species except a significant negative correlation between
Cd and Cu (r = -.0.1995; SI2). This might as well be associated to differences in the feeding
behavior of each species.
MEC is quite a new index but a widely used tool for generating information about heavy metal
origin (Adamu and Nganje 2010). MEC values higher than 1 in this study for both fish and
shrimp species (11.83 and 6.12 respectively; Table 3) support strongly the anthropogenic
source of Heavy metal contamination.
Multivariate analyses
Principal Component analysis
Principal component analysis (PCA) of heavy metals concentration for Ethmalosa Fimbriata,
Clarias Gariepenus, Tilapia Guineensis fishes and Macrobrachium Felicinum shrimp species
performed using SPSS 20 was expected to identify those elements that co-vary. The PCA results
are presented in Fig. 2a where varimax rotation was applied on the first two principal
components; PC1 and PC2 accounting for 70.49 and 23.94 % respectively with an overall
variance of 94.43%. Zn, Cr and Pb with positive loading and clustering together in PCA 1
indicates the strength of their common relationship as compared with the greater distance
observed for Ni. Cu with relative negative loading in PCA 2 reveals the tendency of the fish and
shrimp species in accumulating less Cu than others.
Cluster analysis
The measurement regarding similarities and/or differences between size and heavy metals
concentration for Ethmalosa Fimbriata, Clarias Gariepenus, Tilapia Guineensis fishes and
Macrobrachium Felicinum shrimp species by cluster analysis was carried out to obtain
information on their association and patterns in data. Result of cluster analysis is shown on the
dendogram (Fig 2b) with two main distinguishable clusters. The first cluster comprised of Cd
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
combining first with the smallest distance to Ni and increased slightly to Zn and relates to a
common mixed source of industrial effluents, garbage incinerator and fertilizers application.
The second cluster comprised of Cu having the shortest distance which extended slightly to Cr
and Pb (persistent toxic metals) and associates with mixed source inputs from industrial
effluents and Nigerian crude oils (Farombi et al. 2007).
CONCLUSION
The results revealed that concentration of Cr, Pb, and Ni in fish and shrimp species obtained
from markets in Calabar, Cross River State was high and crosses the threshold according to the
quality standard set. MPI in the order: Ethmalosa Fimbriata > Clarias Gariepenus >
Macrobrachium Felicinum > Tilapia Guineensis advises that Ethmalosa Fimbriata should be
properly processed before consumption and that proper environmental monitoring should be
enhanced to check heavy metal hazard. The EWI of the studied heavy metals by fish and shrimp
consumption was below the PTWI values which indicate a low risk of non-carcinogenic adverse
effects for consumers. More so, the carcinogenic risk of Pb in both fish and shrimp species was
within the acceptable range of 10-4 -10-6 mg/kg/day. The combine heavy metal concentration
and health risk analysis showed that the studied fish and shrimp species could be considered
safe to local people and that there may be no potential risks relating to fish and shrimp intake
in Calabar. Even though, it is recommended to policy makers and all stakeholders to stop the
sources of Cr, Pb, and Ni pollutants, refining, trading and use in all sectors so as not to pollute
the environment and increase health risks to the community. The bioaccumulation patterns of
metals in this study can be utilized as effective indicators of environmental metal
contamination to offer baseline insights on the concentration and health risk of some toxic
heavy metals in commercial fish and shrimp species consumed in Calabar and the globe in
general.
ACKNOWLEDGEMENTS
We are thankful to the management of University of Calabar, Nigeria for the financial support
through Bond Fellowship. The authors acknowledge with thanks the assistance of Dr. Stephen
Oladeji, Miss Anne Ikrihi, and Miss Favour Adagbor, all of Department of Food Science and
Technology, Faculty of Agriculture, University of Calabar for the identification of the fish and
shrimp species used in this study and support during the sampling exercise. The technical staff
of the Institute of Oceanography and Pure & Applied Chemistry Department, University of
Calabar are also appreciated for their assistance in laboratory protocols.
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
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Table 1: Biological background information, sampling location and trophic level characteristics
of the studied fish and shrimp samples
Biological Information and
Trophic level characteristics
Scientific
Name
Clarias
Gariepenu
s
Tilapia
Guineensi
s
Ethmalosa
Fimbriata
Macrobrachiu
m Felicinum
English
Name Cat Fish
Tilapia
Fish Bonga Fish Shrimps
Local
Name
Obubit
Inaha Asat Ekpai Obu
Range of
length
(cm)
40-60 16-46.2 15-25 3.5-9.5
Range of
Weight
(g)
350-550 150-250 100-150 3.70-5.50
Main
Food
Living and
dead
animal
matter,
Agro
products
etc.
Amphibio
us plants Plantons
Worms, living
and dead
organic matter
Habitat
Fresh
water
lakes,river
s,
swamps,
artificial
ponds etc.
Shallow
streams,
ponds,
lakes,
rivers etc
Fresh and
Brackish
water,
Mangrove
creeks,
inland
rivers etc.
Fresh and
Brackish
water,
Mangrove
creeks, inland
rivers etc.
Trophic
level 38 2.8 - 2.5
Location and number
(quantity) of samples collected
Beach
Market 6 6 9 600g
Lagos
Street 6 6 9 600g
Mbukpa
Market 6 6 9 600g
Watt
Market 6 6 9 600g
Total 24 24 36 2400g
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
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Table 2: Descriptive Analysis of the selected Heavy metals
Seafood /Heavy
Metals Conc.
(Mg/Kg) (Pb) (Zn) (Cr) (Cu) (Cd) (Ni)
(H
g) Total
Rang
e
M
PI
Catfish (Clarias
Gariepenus)
5.56±
0.41
0.84
±0.0
7
6.48±
0.29
6.36±0
.73
0.13
±0.1
1
1.12
±0.1
8
N
D
20.48
±0.22
0.13-
6.48
1.
7
5
Tilapia fish (Tilapia
Guineensis)
5.24±
0.43
0.46
±0.0
2
5.14±
0.79
6.25±0
.67
0.03
±0.0
1
1.27
±0.0
8
N
D
18.38
±1.94
0.03-
6.25
1.
2
1
Bonga fish (Ethmalosa
Fimbriata)
6.68±
0.05
1.64
±0.0
2
7.47±
0.02
7.73.0
9±0.49
0.08
±0.0
1
2.3±
0.12
N
D
25.90
±0.28
0.08-
7.73
2.
2
0
shrimps
(Macrobrachium
Felicinum)
5.07±
0.28
0.56
±0.0
8
6.06±
1.01
7.35±0
.57
0.03
±0.0
1
1.3±
0.04
N
D
20.36
±1.63
0.03-
7.35
1.
2
8
Total
22.55
±0.71
3.50
±0.8
7
25.15
±1.01
19.96±
0.86
0.27
±0.0
7
5.99
±0.4
8
N
D
85.12
±9.90
0.27-
25.15
-
Range
5.07-
6.68
0.46-
1.64
5.14-
7.47
6.25-
7.73
0.03-
0.13
1.12-
2.3
N
D
18.38-
25.90 -
-
Coefficient of
variation (%) 12.59
53.4
9 16.96 12.35
102.
31
32.3
2 - - -
-
Table 3: The PTDI, EDI, and EWI values recorded for the different heavy metals detected in the
fish and species
Fish
Heavy Metal EDI (mg/kg bw/day)
EWI (mg/kg
bw/week) PTDI %PTWI K Value MEC
Pb 1.8 x 10-3 5.74 x 10-2 3.57 229.5138
7.02 11.83
Zn 3.15 x 10-4 9.62 x 10-3 1000 0.137495
Cr 2.05 x 10-3 6.26 x 10-2 23.3 0.268832
Cu 2.19 x 10-3 6.67 x 10-2 500 1.907106
Cd 2.51 x 10-5 7.96 x 10-4 0.007 11.36996
Ni 5.03 x 10-4 1.54 x 10-2 0.365 4.210467
Shrimp
Heavy Metal EDI (mg/kg bw/day)
EWI (mg/kg
bw/week) PTDI %PTWI K Value MEC
Pb 1.63 x 10-3 4.99 x 10-2 3.57 199.5815
2.28 6.12
Zn 1.79 x 10-4 5.46 x 10-3 1000 0.078066
Cr 1.96 x 10-3 5.97 x 10-2 23.3 0.25619
Cu 2.37 x 10-3 7.23 x 10-2 500 2.066989
Cd 8.87 x 10-6 2.71 x 10-4 0.007 3.868132
Ni 4.19 x 10-4 1.28 x 10-2 0.365 3.506849
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
Table 4: Estimated CRlim (non-carcinogenic and carcinogenic), CRmm, THQ, CR and HI
Heavy
Metal
(Fish)
Carcinogenic Non-carcinogenic
THQ
CR
(mg/kg/da
y)
CRlim
(Kg/day)
CRmm
(Meals/month)
CRlim
(Kg/day)
CRmm
(Meals/mon
th)
Pb
3.28 x 10-
3 0.44 9.76 x 10-3 1.31 0.54 1.60 x 10-5
Zn 4.99 668.77
1.05 x 10-
3
Cr 7.66 x 10-4 0.10 6.84
Cu 0.10 12.86 0.05
Cd 0.20 26.96 0.03
Ni 0.21 27.92 0.03
HI 7.48
Heavy
Metal
(Shrim
p)
Carcinogenic Non-carcinogenic
THQ
CR
(mg/kg/da
y)
CRlim
(Kg/day)
CRmm
(Meals/month)
CRlim
(Kg/day)
CRmm
(Meals/mon
th)
Pb
3.77 x 10-
3 0.51 1.12 x 10-2 1.51 0.47 1.39 x 10-5
Zn 8.78 1177.88 5.97 x 10-4
Cr 8.04 x 10-4 0.11 6.52
Cu 0.09 11.86 0.06
Cd 0.59 79.24 0.01
Ni 0.25 33.52 0.02
HI 7.06
Fig. 1. Heavy Metal concentrations of the four sampling locations in Calabar
20.03
20.29
22.45 22.36
Beach Market Lagos Street Mbukpa Market Watt Market
Total conc. (mg/kg) per sampling location
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Fig. 2 : (a) Score plot of PCA and (b) Dendogram of clustering of heavy metals in fish and
shrimps species
SI1: Anova: Two-Factor With
Replication
SUMMARY
Lead
(Pb)
Zinc
(Zn)
Chromium
(Cr)
Copper
(Cr)
Cadmium
(Cd)
Nickel
(Ni) Total
Catfish (Clarias Gariepenus)
Count 4 4 4 4 4 4 24
Sum 22.23 3.37 25.92 25.42 0.53 4.46 81.93
Average 5.5575 0.8425 6.48 6.355 0.1325 1.115
3.4137
5
Variance
0.22735
8
0.0060
92 0.113867 0.706967 0.015692
0.04083
3
8.0250
07
Tilapia fish (Tilapia
Guineensis)
Count 4 4 4 4 4 4 24
Sum 20.97 1.82 20.54 25.01 0.13 5.07 73.54
Average 5.2425 0.455 5.135 6.2525 0.0325 1.2675
3.0641
67
Variance
0.24189
2
0.0005
67 0.827033 0.605292 0.000025
0.00942
5
6.9024
17
shrimps (Macrobrachium
Felicinum)
Count 4 4 4 4 4 4 24
Sum 20.27 2.22 24.25 29.39 0.11 5.2 81.44
Average 5.0675 0.555 6.0625 7.3475 0.0275 1.3
3.3933
33
Page 16 of 17
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Oyo-Ita, I. O., Nkom, P. Y., Umo, F. E., Eton, E., Neji, H. A., & Oyo-Ita, O. E. (2022). Residue Levels and Human Health Risk Assessment of Heavy
Metals in Commercial Fish and Shrimp Species from Calabar, Nigeria. European Journal of Applied Sciences, 10(1). 446-462.
URL: http://dx.doi.org/10.14738/aivp.101.11613
Variance
0.10809
2
0.0094
33 1.368092 0.432225 9.17E-05
0.00186
7
8.8294
93
Bonga fish (Ethmalosa
Fimbriata)
Count 4 4 4 4 4 4 24
Sum 26.73 6.54 29.88 30.92 0.31 9.2 103.58
Average 6.6825 1.635 7.47 7.73 0.0775 2.3
4.3158
33
Variance
0.00375
8 0.0007 0.0004 0.0118 9.17E-05
0.01786
7
9.8167
47
Total
Count 16 16 16 16 16 16
Sum 90.2 13.95 100.59 110.74 1.08 23.93
Average 5.6375
0.8718
75 6.286875 6.92125 0.0675
1.49562
5
Variance 0.53738
0.2320
03 1.212343 0.778892 0.005087
0.24925
3
ANOVA
Source of Variation SS df MS F P-value F crit
Sample
20.7744
4 3 6.924812 34.99251 4.62E-14
2.73180
7
Columns
747.744
3 5 149.5489 755.7015 1.01E-60
2.34182
8
Interaction
10.2015
4 15 0.680103 3.436702 0.000212
1.80757
1
Within
14.2483
8 72 0.197894
Total
792.968
7 95
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SI2: Pearson Correlation of the Studied Samples
Heavy Metals r N
T- statistics DF P-value
Pb with Zn 0.9051615 16 7.9676815 14 1.43549E-06
Pb with Cr 0.7217816 16 3.9020055 14 0.001595445
Pb with Cu 0.6024922 16 2.8245199 14 0.013511874
Pb with Cd 0.2418904 16 0.9327711 14 0.366746797
Pb with Ni 0.811882 16 5.2032761 14 0.000133782
Zn with Cr 0.7359713 16 4.0675047 14 0.001153082
Zn with Cu 0.5078501 16 2.2058286 14 0.044610069
Zn with Cd 0.2898834 16 1.1333062 14 0.276121143
Zn with Ni 0.8787202 16 6.8879414 14 7.46654E-06
Cr with Cu 0.7485358 16 4.2237796 14 0.000850332
Cr with Cd 0.2747822 16 1.0693018 14 0.303024301
Cr with Ni 0.6002304 16 2.8079276 14 0.013960744
Cu with Cd -0.1994891 16
-
0.7617307 14
Cu with Ni 0.5656931 16 2.5668069 14 0.022375583
Cd with Ni 0.1374725 16 0.5193056 14 0.611659589