Body Levels of Heavy Metals in Children from Public Schools within Owerri Municipal, Imo State Nigeria
Verla Andrew Wirnkor1*, Verla Evelyn Ngozi2
1Department of Chemistry, Imo State
University, Owerri, Imo State, Nigeria
2Department of Environmental Technology, School of Environmental Technology Federal University of Technology, Owerri, Imo State Nigeria
*Corresponding author: Verla Andrew Wirnkor, Department of Chemistry, Imo
State University, Owerri, Imo State, Nigeria. Tel: +23470353816097; Email: verngo@yahoo.com; n.verla@evtfuto.com
Received Date: 03 May, 2018; Accepted Date: 17 July,
2018; Published Date: 25 July, 2018
Citation: Wirnkor VA, Ngozi VE (2018) Body Levels of Heavy Metals in Children from Public Schools within Owerri Municipal, Imo State Nigeria. Arch Anal Bioanal Sep Tech: AABST-106. DOI: 10.29011/AABST-106. 100006
1. Abstract
Despite children’s special vulnerability, exposure to heavy metals through playgrounds soils has been overlooked in most third world countries primarily due to lack of information. In a two-year study within Owerri municipality, 4134 children from 9 public schools were physical examined and 99 children subjected to heavy metal test using Quantum Magnetic Resonance Analyzer, Model QMRA 918. A total of 45 soil samples from school playgrounds were digested with nitric acid and hydrochloric acid and metal concentrations determined using An Analyst 400 Perkin Elmer AAS. Heavy metals concentrations in children were compared within each school, amongst school playgrounds and with upper limit of normal concentration in children. Children at Housing Estate Owerri had low concentration of metals whereas mean values of manganese and copper were higher than upper limit of normal concentration in both years. In terms of mean metal concentration in children’s body, metals ranking followed the trend: Ni (4.67 mg/Kg) > Co (4.08 mg/Kg) > Zn (1.55 mg/Kg) > Mn (1.31 mg/Kg) > Cu (1.28 mg/Kg). Manganese, cobalt and zinc showed a week negative correlation whereas copper and nickel had a week positive correlation. Heavy metals in some children were found to be slightly higher than upper limit of normal concentration while most metal concentrations were lower than required for healthy living. There was a general decrease in metal concentration from 2012 to 2013. Children at public schools within the municipality could be at risk due to elevated concentrations of manganese, cobalt and copper. Therefore, there is the need for playgrounds to be periodically monitored and mitigation put in place to reduce increasing concentrations of these heavy metals.
2. Keywords: Children; Exposure; Normal concentrations; Toxic metals
3.
Introduction
Tiny amounts of metallic elements are necessary for good health in humans
and other mammals yet may be injurious in excess [1,2].
The importance of metals in body metabolism cannot be over emphasized. However,
both deficiency and excess of these metals produce undesirable effects [3-5]. Metals are ubiquitous in nature and so elevated
amounts in soils are often linked to anthropogenic sources. Children’s nervous
and digestive system are still developing and so are susceptible to metal and
organic substance intake. Children have the propensity to explore the world
through their mouth [6]. They are exposed to
heavy metals via absorption through skin, food, ingestion of treated materials
e.g. wood, contaminated soil and inhaling of contaminated air. Infant and
children are particularly susceptible to neuron-toxicological damage from metal
exposure throughout their ongoing intellectual development. Reviewed
literatures reveal that children’s play grounds could be a veritable source of
metal enrichment in the bodies of children [3,7-9].
Few studies have investigated children’s playgrounds in Nigeria. It is
regrettable that no research existed on children’s play grounds in Imo state as
at the time of this research. However public schools presented themselves as
appropriate targets for assessing heavy metal content of children and their
playgrounds [10]. These playgrounds represent
places where urban children spent most of their time when outdoor but are
assessable to everyone at all times [9].
conducted a risk-based exposure of children to trace metals in playgrounds in
urban Madrid concluded that ingestion of substrate particles was the highest
contributor to the overall figure of heavy metals risk followed by dermal
adsorption. Inhalation of resuspended particles through the mouth and nose was
almost negligible when compared to the other exposure pathways. African
children are more likely to perform pica activities than their counterparts
elsewhere as a result of hunger, poor parental attention, warm climate that
encourages outdoor activities, poor environment and non-regulated play at
playgrounds amongst other reasons. All these factors generally support the
existence of a huge gap of knowledge about children playgrounds especially
Nigeria and Owerri municipal in particular. Therefore, the importance of this
work, the first of its kind as far as could be established cannot be
overemphasized.
4.
Materials and Methods
Study area: The study area is
Imo State, southeast Nigeria, bounded by Latitudes 40401
and 80151
N and longitudes 60401 and 80151E. It lies within the humid tropics. Owerri
municipal is one of the three Local Government Areas (LGAs) that make up Owerri
city, the capital of Imo state of Nigeria set in the heart of the Igbo land.
Its population density ranks fourth as of 2006 census [11].
This
area is under heavy traffic all year round since it is home to the biggest and
modern market and the seat of state government. There are no industries but
connecting roads to neighboring states pass through the municipality thereby
increasing traffic volume. In addition heavy construction of roads, hotels and
estates can be observed by a visitor all year round. The study area falls
within the most affected area in the pollution map of Nigeria [11].
4.1.
Demography
4.1.1.
Body
Concentrations of Heavy Metal in Children (BCHMC): All children
between 4 to 12 years selected for testing were first examined physically using
the parameters listed as typical symptoms of high levels of heavy metals in
children compile from literature.
Teachers from participating schools’ teachers were also asked to
complete a short questionnaire designed to identify children with possible
symptoms of metal exposure. Children with 4/9 positive results were considered
as cases for testing and thus were tested in situ using QRMA instrument.
4.1.2.
Procedure for Quantum Resonance Magnetic Analyzer: After installing the software in PC, the USB drive was connected to PC.
The metal stick line to instrument was handed to a child and then the software
opened (Plate 1). The start testing option was chosen and in 1 minute, the
instruments auto-showed the test results of all five metals in mg/Kg units.
4.2.
Ethical considerations
Permission was obtained from school
principles and parents consent was sought children accepted willingly to take
part in the study before start of data collection. Study approval was also
obtained from relevant government bodies. The names of the schools that
participated in the study including their locations were kept open during data
analysis and compilation of the final report.
4.3. Determination of heavy metals in playground soils
4.3.1.
Soil sample collection and treatment: Soil
samples at 0-5 cm depths were collected in the months of June and September
(rainy season), in January and March (dry season), of 2012, 2013 and in
February (dry season). At each sampling
site, a “W” shaped line was drawn on a 2 x 2 m surface along which samples were
collected from five points into previously treated polythene containers using a
perforated container to allow water to drain for rainy season samples. These
samples were sun/air dried for two days, and then oven dried at 50oC for 2 days;
ground in acid-washed porcelain mortar with pestle. The samples were sieved
through a 2 mm sieve in order to normalize variations in grain size
distributions. The samples were stored in polythene containers with caps for
further analysis.
4.3.2.
Determination of total heavy metal: The total
heavy metal in all 45 soil samples were determined by first digesting with nitric acid and hydrochloric then manganese,
cobalt, nickel, copper and zinc concentrations were determined using An Analyst
Perkin Elmer 400 Atomic Absorption Spectrometer.
Quantification was carried out using appropriate calibration curves prepared in the same acid matrix with
standard metal solutions for atomic absorption spectrophotometer.
5.
Results
and Discussion
Considering the
upper limit of normal concentration of metals in children (ULNCC) to be 0.88
mg/kg, 5.73 mg/kg, 5.53 mg/kg, 0.75 mg/kg and 1.99 mg/kg for Mn, Co, Ni, Cu and
Zn respectively, the measured body levels of heavy metals (BLHMs) in children
were selected and expressed as percentages of children with heavy metals above
normal range (Table 2). While schools, WBP and
WSP had 4% of children heavy metal level above normal range. The low percent
children with metal above normal range estimated for WBP and WSP could be
attributed to the fact that the schools were newly opened, and so the soil have
not been impacted by anthropogenic activities. Schools UPS and CSO had highest
values of 17.6 and 16% respectively. Schools UPS and CSO are at commercial
centers and surrounded by petrol stations and heavy traffic all year round.
Atmospheric deposition and commercial activities could be responsible for the
abnormal rise in body levels of heavy metals in children at the two schools. On
the other hand, no case was recorded for schools HEO and MNO. Mostert, 2009
suggested that play grounds within commercial centers are likely to have
children with elevated blood lead levels. This may be the case with schools UPS
and CSO in which children showed elevated concentrations of body metals. (Table 2) equally shows the mean values of body heavy
metals in children. Out of 4134 children screened using symptoms compile from
literature, 183 were found with body levels of heavy metal above normal range
in children. Eleven children were taken from each school where then subject to
testing by QMRA instrument. Considering individual schools the total percent of
children with metal levels above ULNCC was 65.4%. This value is cannot be
overlooked.
5.1.
Heavy Metal in
Children’s Body in 2012
(Figures 1 to 9 shows) bar charts of metal concentration
in children’s body in 2012. Metal concentrations in children at HOE were
plotted as each metal in all children (Figure 1)
showed that Nickel was highest for all children and highest amongst all five
metals followed by Cobalt. At HOE the depressing order of metal concentration
in children was Ni > Co > Zn > Cu > Mn. Figure 2 shows that an
overall total concentration of cobalt was slightly higher than Ni. Again, Mn
was the least amongst all five metals in children at MNO. The decreasing order
of metal in children for MNO was Co > Ni > Zn > Cu > Mn. Figure 3
again shows Nickel to top the list amongst five metals in children’s bodies at
CSO and was closely followed by Cobalt. The order of decreasing metal concentration
in children’s body at CSO was Ni > Co > Zn > Cu > Mn. Figure 4
shows bar chart of metals concentration in children’s bodies at SCP. Results
are much similar to those in CSO above. However, copper was the lowest metal
for children at CSO. The order of decreasing metal concentration here was Ni
> Co > Zn > Mn > Cu. (Figure 5)
shows metals in mg/kg concentrated in children’s body for TSO. Result shows
that Mn was the least as have been seen in children of other playgrounds. Here
the decreasing order of metals was Ni > Co > Zn > Cu > Mn (Figure 6). Shows that Nickel was the highest metal in
children as WSP while Mn the lowest. However, the concentration of Mn and Zinc
were much elevated in than WSP. The order of decreasing concentration of metals
in children at WSP was Ni > Co > Zn > Mn > Cu (Figure 7). Shows that Ni was highest followed by
cobalt and Zn while copper was lowest at WBP. Decreasing order of metals
concentration was Ni > Co > Zn > Mn > Cu (Figure
8). Shows similar bar charts for metals concentration in children at IKS
Nickel again was highest while copper was lowest. The decreasing order was Ni
> Co > Zn > Mn > Cu. At UPS metal concentration in children was in
the decreasing order of Ni > Co > Zn > Mn > Cu.
Copper was lowest in children’s body
at SCP, WBP and UPS while Magnesium was lowest in children’s body at HOE, MNO,
CSO, TSO and WSP.
5.2.
Heavy Metal in
Children’s Body in 2013
The concentrations
of heavy metals in children’s body were plotted against each child for HEO (Figure 10). The bar chart shows that Nickel was the
highest metal except child F, G and L where cobalt was highest. Copper was the
lowest metal in the body of children where child C had the lowest concentration
of copper. The decreasing of metals in children was Ni > Co > Zn > Mn
> Cu (Figure 11). Shows that Nickel was
highest in five children while cobalt followed as highest in four children the
order of decreasing concentration for metals in children at MNO was Ni > Co
> Zn > Mn > Cu (Figure 12). Shows that
nickel was highest overall and child B had the high concentration whereas in
child C and E nickel compared well with cobalt. The concentration of metals in
children at SCP for 2013 showed the decreasing order Ni > Co > Zn > Mn
> Cu (Figure 13). Shows the concentration of
metal in children at CSO in 2013 as expected, Ni topped the chart followed by
cobalt. The decreasing order was Ni > Co > Zn > Mn > Cu (figure 14). In the concentrations of metals in
children’s body at TSO are shown in the bar chart. Nickel was highest overall
and highest for child A, B, G, H, J, K while cobalt was highest for child C and
D. The order of decreasing concentration for TSO children was Ni > Co >
Zn > Mn > Cu (Figure 15). Shows that metal
concentration in children could be ranked in decreasing order out WSP as
follows: Ni > Co > Zn > Mn > Cu in child D and E copper was highest
than other metals except Nickel (Figure 16). Shows
that Nickel was highest followed closely by cobalt. The decreasing order of
metal concentration in children at WBP was Ni > Co > Zn > Mn > Cu.
At IKS (figure 17) it was deduced that the
decreasing order was Ni > Co > Zn > Mn > Cu. Values of Ni and Zn
were generally high at IKS.
The concentration
of metals at UPS show that nickel was highest as usual followed by zinc. Copper
and magnesium values here were higher than for many playgrounds. Mean values of
heavy metals in children for March, 2012 and Feb-March 2013 have been
summarized in (table 5).
Manganese ranging
from 0.71 mg/Kg for HEO to 3.94 mg/Kg for CSO with an average value of 1.59
mg/Kg, cobalt had a ranged from 3.58 mg/Kg for HEO to 6.23 mg/Kg for TSO;
copper ranged from 0.50 mg/Kg for HEO to 1.23 mg/Kg for IKS and Zinc ranged
from 1 mg/Kg for HEO to 2.67 mg/Kg for CSO. It was observed that children at
playground HEO had lowest content in their bodies amongst all others. From the
average metal concentration in children’s bodies during Feb – March, 2013 those
playgrounds could be ranked in order of decreasing concentration as follows
CSO>IKS>TSO>UPS>WSP>WBP>SCP>MNO>HEO. Ranking metals in
decreasing order of average concentration in children gives Ni > Co > Zn
> Mn > Cu. Ni (5.18 mg/Kg) > Co (4.18 mg/Kg) > Zn (2.18 mg/Kg) >
Mn (1.59 mg/Kg) > Cu (1.02 mg/Kg): Feb – March, 2013. Results of analysis summarized
in (table 5). For Feb-March, 2013 for body
concentrations of heavy metals in children’s body indicate that Magnesium
ranged from 0.81 mg/Kg at TSO to 2.39 mg/Kg at WBP. Ranking children at various
playgrounds in order of decreasing body metal concentration was observed as follows:
SCP>WSP>IKS>UPS>TSO>CSO>WBP>MNO>HEO
Considering
average metal concentration in children’s body, the ranking of metals was
observed to follow the trend: Ni (4.67 mg/Kg) > Co (4.08 mg/Kg) > Zinc
(1.55 mg/Kg) > Mn (1.31 mg/Kg) > Cu (1.28 mg/kg) compared with Upper
Limit of Normal Concentration in Children’s body’s (ULNCC).
Figure
19
compares the average metal concentration in children’s body for 2012 and 2013
with the upper limit of metal concentration in children according to QMRA model
918.The bar chart shows that magnesium was higher in both 2012 and 2013 than
the ULNCC. As pointed out by WHO 1981; Needleman, 1987 and Newman, 2008, excess
magnesium in children may be linked to low IQ and low growth amongst other
factors such as carbohydrate and lipid metabolism associated problems. Average
cobalt concentration for 2012 and 2013 in children of all playground public
schools studied were lower than ULNCC of 5.73 mg/Kg even though figure 19 shows
that Cobalt during 2013 was higher than for 2012, values were significant (P
> 0). With increasing commercial activities, burning of refuse and other
anthropogenic activities Cobalt concentrations may likely reach upper limits
within a near future. Average Nickel concentrations in 2012 and 2013 in
children’s body at all nine playgrounds were 5.18 mg/Kg and 4.67 mg/Kg
respectively. These values were slightly lower than ULNCC. Average Copper concentrations in Children’s
body for 2012 and 2013 were higher than nickel limit of normal concentration in
children of 0. 1 mg/Kg. Figure 19 equally Shows that Nickel content in Children
within public schools in the municipality compared well for 2012 and 2013.
Average Zinc concentration in children was higher than for 2013. However, the
ULNCC of 1.99 mg/Kg was higher than average Zinc concentration in 2013. The
value for average Zinc concentration in Children in 2012 of 2.18 mg/Kg is
likely a problem for the children.
In order to find
out the extent to which metal concentrations in playgrounds soil relate to
metals concentration in children figures 20 to 29 were plotted. Result showed
that all five metals concentrations in children correlated with metals
concentrations in playground soils. However, Mn, Co and Zn had weak negative
correlation in 2013 whereas all others had weak positive correlations with the
highest being zinc (R2 = 0.264) in 2012. The weak correlation could
be so because uptake of metals into children’s body could occur not only from
ingestion of soil during play but through foods, fruits and from playing with
toys for instance [7]. 2013 determined nickel
concentrations of 1.76 mg/Kg in pineapple (Ananas cosmosus) and 2.65 mg/Kg
in beans (Phaseolus
vulgaris) which is one of the common fruits in Owerri municipality.
Until the current investigation, data on metal levels in children and surface
soil of children’s playground from the area under study were scarce. Therefore,
current results should be of a special interest as reference values in future
evaluations of the playground soils, which we deemed very necessary.
6.
Conclusions
From the analysis
and examination of data in this work the following conclusions were made in most of the nine playgrounds, all
children had Ni as the highest metal concentration while Cu and Mn were the
lowest in some cases. Children
in playgrounds of public schools within Owerri municipality could be at risk of
Mn, Cu and Zn toxicity problems. Even at MNO where the trend in metal was
radically different, Zn was still the third metal in all children. Three trends
were observed in metal concentration in the year 2012, dominated by Ni>Co>Zn>Mn>Cu,
where as all playgrounds showed same trend in 2013 Ni>Co>Zn>Mn>Cu.
Even though they were all weak correlations, metals concentrations in soil had
either a positive or a negative correlation with metal concentrations in
children.
7.
Recommendation
As a way of
monitoring the influence of playgrounds on children’s body level of heavy
metals this study underlines the need for replicating periodic studies. More
detail work is required such that urine and even blood samples be used to
ascertain the actual situation as concerns heavy metals levels in children.
8.
Competing
interests
The authors’ confirms that there is no conflict of interest
regarding the submitted manuscript.
9.
Authors’
contributions
E N collected prepared the consent letter and meet the head teachers
and parents, she also studied the use of the MRA analyzer and helped perform
the analytical determinations, acquired and analyzed data and contributed to
the writing of the manuscript and revision. AW organized the experimental
setting, supervised the work and wrote the manuscript.
Figure1: Map of Owerri
Metropolis showing, names, the sample locations.
Plate 1: Quantum
Bio-electric Sensor.
Figure 1: HM concentration in children at HEO.
Figure 2: HM concentration in children at MNO.
Figure 3: HM concentration in children at CSO.
Figure 4: HM concentration in children at SCP.
Figure 5: HM concentration in children at TSO.
Figure 6: HM concentration in children
at WSP.
Figure 7: HM concentration in children at WBP.
Figure 8: HM concentration in children at IKS.
Figure 9: Heavy metals concentration in children at UPS.
Figure 10: HM concentration in children at HOE.
Figure 11: HM concentration in children at MNO.
Figure 12: HM concentration in children at SCP.
Figure 13: HM concentration
in children at CSO.
Figure 14: HM concentration in children at TSO.
Figure 15: HM concentration in children at WSP.
Figure 16: HM concentration in children at WBP.
Figure 17: HM concentration in children at IKS.
Figure
18:
HM concentration in children at UPS.
Figure 19: Average metal in
children and upper limit of normal concentration in children’s body’s (ULNCC).
Figure 20: Mn in children soil against Mn.
Figure 21: Con in soil against cobalt in children.
Figure 22: Ni in soil against nickel in children.
Figure 23: Cu in soil against copper in children.
Figure 24: Zn in soil against zinc in children.
Figure 25: Mn in soil against manganese in children.
Figure 26: Con in soil against cobalt in children.
Figure 27: Ni in soil against nickel in children.
Figure 28: Cu in soil against copper in children.
Figure 29: Zn in soil against zinc in children.
S/No |
School playground Codes |
Land use |
No of Children on role |
Cases of heavy metals above normal range |
Percent children with metal above normal range |
1. |
HEO |
R |
470 |
00 |
00 |
2. |
MNO |
R |
1260 |
00 |
00 |
3. |
SCP |
GRA |
326 |
17 |
5.2 |
4. |
CSO |
Busy high way |
241 |
39 |
16 |
5. |
TSO |
Busy high way |
276 |
35 |
12 |
6. |
WSP |
NP |
579 |
25 |
4.3 |
7. |
WBP |
R/CC |
387 |
16 |
4.1 |
8. |
IKS |
NP |
470 |
29 |
6.2 |
9. |
UPS |
NP |
125 |
22 |
17.6 |
R: residential area; GRA: government residential area; R/CC: Residential/ commercial area; NP: Nigeria police station |
Table 1: List of schools land use and cases of metals above normal range.