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International Journal of Environmental Health Research
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/cije20
Heavy metal analysis of drinking water supply,
wastewater management, and human health risk
assessment across secondary schools in Badagry
coastal community, Lagos State, Nigeria
Elizabeth O. Oloruntoba, Ojima Zechariah Wada & Mumuni Adejumo
To cite this article: Elizabeth O. Oloruntoba, Ojima Zechariah Wada & Mumuni Adejumo (2021):
Heavy metal analysis of drinking water supply, wastewater management, and human health risk
assessment across secondary schools in Badagry coastal community, Lagos State, Nigeria,
International Journal of Environmental Health Research, DOI: 10.1080/09603123.2021.1926438
To link to this article: https://doi.org/10.1080/09603123.2021.1926438
Published online: 18 May 2021.
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Heavy metal analysis of drinking water supply, wastewater
management, and human health risk assessment across
secondary schools in Badagry coastal community, Lagos State,
Nigeria
Elizabeth O. Oloruntoba
a
, Ojima Zechariah Wada
a,b
and Mumuni Adejumo
a
a
Department of Environmental Health Sciences, Faculty of Public Health, College of Medicine, University of Ibadan,
Ibadan, Nigeria;
b
Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa
University, Doha, Qatar
ABSTRACT
This cross-sectional study was conducted to evaluate drinking water and
wastewater management facilities, as well as the health risk associated
with heavy metal contamination of available water sources among
Badagry schools. According to Joint Monitoring Program classication,
majority (60%) of the schools provided basic water service, 10% limited
service, whereas 30% provided no service. Water quality parameters such
as pH, Pb, Cr, Cd, and E. Coli count were above the permissible limits in
both public and private schools. None of the schools had wastewater
management facilities, thereby leading to ponding. Pb and Cr posed
a carcinogenic risk to the consumers as they exceeded the permissible
10
−5
. Even though majority of the schools provided basic water service,
the contamination of majority of the water sources and the absence of
structured-drainage channels in all the schools was bothersome. Prompt
intervention is required to safeguard and maintain the integrity of the
students’ health.
ARTICLE HISTORY
Received 17 October 2020
Accepted 1 May 2021
KEYWORDS
Coastal communities; school
drinking water; human
health risk assessment;
wastewater management
Introduction
Children are in the school environment for a significant period of their childhood, which is why it is
paramount for schools to provide adequate facilities required to safeguard their health and improve
their learning outcome. The National Policy Guidelines on School Sanitation put in place by the
Nigerian Government, echoes the importance of providing potable water, as well as adequate and
functional drainage systems to effectively manage wastewater, so as to curb the prevalence of
childhood illnesses like malaria and diarrhoeal diseases, which negatively impacts school absentee-
ism (FMOE 2006). The availability of water at schools has been revealed to make schools more
accessible for students and increases their learning outcome (WHO/UNICEF 2018). The lack of safe
and adequate water supply at schools has also been revealed to be harmful to the health of school
children (UNICEF 2012). Diarrhoeal diseases, malaria and helminth infections force many school
children to be absent from school. It has also been proven that ensuring students stay hydrated
while at school could improve their cognitive ability (Edmonds and Burford 2009; Fadda et al.
2012). Long-term exposure to chemical contaminants in water (e.g. lead and arsenic) may impair
CONTACT Ojima Zechariah Wada ojimawada14@gmail.com Janoubi Student Housing Village, Education City, Qatar
Foundation, Doha, Qatar
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH
https://doi.org/10.1080/09603123.2021.1926438
© 2021 Informa UK Limited, trading as Taylor & Francis Group
learning ability, whereas others like chromium and cadmium have also been revealed to be toxic
and carcinogenic (Adams ; Iqbal and Shah 2013).
The introduction of heavy metals into the groundwater via natural (geogenic) or anthropogenic
processes is of public health importance. This makes it important to routinely test the quality of
drinking water sources. The conventional method of assessing the health impact of heavy metals in
drinking water by solely comparing it against local, national and international permissible limits
have been revealed to be insufficient in providing information about the hazard levels and which of
the contaminants is of the greatest immediate concern (Edokpayi et al. 2018). Health risk assess-
ment is used to predict the likelihood of a health event occurring and the probable extent of adverse
health effects over a timeframe; and has been proven to be effective in regulatory decision-making
(Clark and Barone 2011; Belkhiri et al. 2018). The potential carcinogenic and non-carcinogenic
effects of heavy metals in drinking water are measured via guidelines developed by the United States
Environmental Protection Agency (USEPA) based on the routes of exposure (US Epa 1989). The
common exposure routes are via direct ingestion, inhalation, and dermal absorption (US Epa 1989;
USEPA 2005; Naveedullah et al. 2014; Edokpayi et al. 2018). However, for day school students the
most common exposure route is via direct ingestion.
According to the Joint Monitoring Programme (JMP) Global Baseline report for school WASH
(Steele 2018), it was estimated that about 70% of schools had water sources that provided basic service,
whereas just around 11% and 19% of the schools provided limited and no drinking water services,
respectively. However, data regarding the provision of basic water service in Nigerian schools were
unavailable due to insufficient data. It was estimated that 50% of the schools in Sub-Saharan Africa
(SSA) provided water with limited service whereas the remainder provided no service. A study carried
out by Olukanni (2013) among public schools in Lagos and Ogun State reported that only 25% of the
schools had drinking water points (Olukanni 2013). A WASH survey across schools in Ibadan North
Local Government Area (LGA) in Ibadan reported that in over 90% of the schools, the students’
sources of drinking water was either water brought from their homes or via purchased packaged water
at school (Egbinola and Amanambu 2015). Another survey among selected schools in Ibadan revealed
that the sources of water varied between surface water, wells and tap water supply (Ana et al. 2008).
Coastal regions are susceptible to having peculiar water supply and wastewater management issues
because of the presence of waterbodies like the sea water and swamps, porous soil, stagnant water due
to poor drainage and occurrences of saline intrusion. In some of the coastal communities within sub-
Saharan Africa, presence of poor drainage and wetlands with patches of stagnant water propagated the
breeding of water – related insect vectors, which has led to a high incidence of vector-borne diseases
such as malaria, dengue hemorrhagic fever, river blindness, and onchocerciasis especially during the
raining season (Hardoy et al. 1990; Food and Agriculture Organization of the United Nations (FAO)
2001). A research carried out to determine the prevalence of water-borne diseases in coastal commu-
nities in Sri Lanka revealed that diseases like shigellosis, cholera, hepatitis A and E and typhoid fever
were prominent in the area due to factors like poor drainage management, over population and the
lack of awareness about water-borne diseases among residents (Fowsul 2017). In Nigeria, communities
such as Burutu in Delta State and Aiyetoro in Ondo State have experienced difficulties in accessing
potable water due to saline intrusion. The inhabitants depended on rain harvesting and water purchase
from merchants from the neighboring communities (Oteri and Atolagbe 2003; Adeyemo and Omosuyi
2018). Salt water intrusion has also been found to occur in the confined aquifers of the Coastal Plain
Sands in a zone stretching from Apapa to Lekki within Lagos metropolis (Oteri and Atolagbe 2003).
This survey aimed to evaluate the status of drinking water supply and wastewater management
among secondary schools in a marginalized coastal community in Nigeria’s commercial capital,
Lagos State. A human health risk assessment was also conducted to identify the potential harm the
drinking water sources could pose to the consumers. The study community recently had an episode
of cholera outbreak, after which recommendations were made to the government to implement
sustainable Water, Sanitation and Hygiene (WASH) services (UNICEF 2015a). Results from this
survey will be useful in informing decision-making processes as future interventions are planned.
2E. O. OLORUNTOBA ET AL.
Methods
Sampling sites
The study was carried out in Badagry coastal community, one of Lagos’ 20 LGA. The LGA consists
of some of the few rural areas in Nigeria’s commercial capital city (Ogunbiyi 2017). It lies close to
the Republic of Benin border at Seme. The population of Badagry residents as at 2006 was 241,093
(National Population Commission N 2006). Badagry is 69.19 km southeast of Lagos, 51.49 km west
of Seme and bordered by the Gulf of Guinea to the south (Pollard 2018). Badagry is situated on
latitude: 6° 24ʹ 54.07” N and longitude: 2° 52ʹ 52.75” E. Badagry LGA consists of 11 wards, namely
Ajara, Ajido, Apa, Awhanjigoh, Ibereko, Ikoga, Ilogbo Araromi, Iworo Gbanko, Iya Afin, Keta east
and Posukoh. As at the time of the survey, there were 13 public secondary schools and about 30
registered private schools. A total of 10 schools (five public schools and five private schools) were
selected using a two-stage sampling technique:
STAGE 1 – Selection of wards: this was done by selecting 5 of the 11 wards via simple random
sampling. STAGE 2 – Selection of secondary schools – the secondary schools in the selected wards
were stratified into public and private schools, after which one public and one private school were
selected from each ward by simple random sampling. Ten schools were selected in total, two from
each ward. The public schools selected were school A1, A2, A3, A4, and A5, whereas the private
schools were B1, B2, B3, B4, and B5.
Data collection procedure
Participant and environmental observation
An observational checklist adapted from WASH in Schools Monitoring Package by UNICEF
(UNICEF 2011) and Nigeria Policy on School Sanitation (FMOE 2006) was used to assess sources
of water supply, and wastewater management facilities.
Sanitary inspection of water sources
Sanitary inspection forms were used to assess whether the schools’ drinking water sources had
potential risk of contamination. This form was adopted from the WHO Water Safety Plan (WHO
2005). The questions were designed to look-out for contaminations or sources of contamination
around the borehole sources of groundwater. The observations were analyzed using descriptive
statistics via measures of proportion.
Water sample collection
Water samples were collected from each of the school’s main drinking water source during the 2018
rainy season. Grab water samples were collected in order to ascertain the quality. Replicate samples
were collected between August and September 2018. Water samples were only obtained from eight
schools, the remaining schools did not have a drinking water source. During each point of sample
collection, two separate samples were obtained, stored in a cooler box containing ice packs then
transported to the laboratory. The samples collected were:
(a) Bacteriological sample: Samples were collected into sterilized glass bottles, labeled appro-
priately and then placed in a cooler box with ice packs for transportation to the laboratory.
(b) Physico-chemical sample: The water samples were collected in plastic bottles, labeled
appropriately and then transported to the laboratory.
A total of 15 samples were collected within fourweeks; nine from the five public schools and six
from the three private schools with a drinking water facility. One of the public schools had no water
available during the second visit.
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 3
Water sample analysis
The time duration between the water sample collection and analysis was about 24 hours. The
parameters this study tested for are:
(a) Physico-chemical parameters: pH, total dissolved solid (TDS), electrical conductivity (EC),
chloride, hardness, salinity, nitrate, chromium, cadmium, lead, and iron. The pH, TDS, and
EC were measured using a Hanna HI9813-6 digital multimeter. Chloride was determined
using Argentometric method, whereas the salinity was estimated using the salinity formula
(Salinity (mg/l) = 1.8055 Cl
−
). The total hardness and nitrate levels of the water samples were
determined using the EDTA and phenol di-sulfonic acid methods, respectively. The heavy
metals (Cr, Cd, Pb and Fe) were measured via photometric method, using Flame Atomic
Absorption Spectrophotometer (FAAS).
(b) Microbial parameters: Escherichia coli, and total coliform count. Most Probable Number
(MPN) was used to assess the microbial quality of the water samples. Presumptive test was
used to detect the presence of coliform in the water sample by inoculating the samples into
MacConkey broth medium. Gas production and color change after the 24 to 48 hours
incubation period implied a positive reaction. Confirmatory test was used to ascertain the
presence of E. Coli by inoculating positive presumptive tests into brilliant green bile broth.
The MPN of coliform/100 ml of sample was determined using the McGrandy’s Table of
Most Probable Number.
The parameters measured were compared to the guidelines/standards set by the World Health
Organization (WHO) and Standards Organization of Nigeria (SON) for drinking water quality.
Data management and analysis
Data from the observational checklist and water quality results were entered and analyzed using
Statistical Package for the Social Sciences (SPSS) 20. Pearson correlation was used to determine the
correlation between each of the water quality parameters, whereas linear regression was used to
measure the association between the chloride/salinity levels and their respective distance to the
ocean. They were measured at 5% level of significance.
JMP ladder for drinking water in schools
The schools’ water supply facilities were also categorized using the JMP service ladder for schools.
Schools with an improved drinking water source (sources that had the potential to deliver safe water
by nature of their design and construction) with water available at the time of the survey were
classified as having a ‘basic’ service. Schools without water available, but with an improved source
were classified as having a ‘limited’ service, and those with unimproved or no water source are
classified as having ‘no service’ (Steele 2018).
Classification of drinking water quality based on level of microbial contamination
This classification was done based on WHO microbial level classification for drinking water (WHO
2004). The water samples were graded into Excellent (Class-1), Satisfactory (Class-2), Suspicious
(Class-3) and Unsatisfactory (Class-4). Water samples with any E. Coli count was automatically
classified as Unsatisfactory, whereas water samples with no E. Coli count and maximum of 10 total
coliform count were classified as Excellent.
Quantitative health risk assessment
A school-WASH survey in the study location had revealed that about 55% of the students drank
water from the sources where the water samples were obtained (Wada et al. 2019). The probable
4E. O. OLORUNTOBA ET AL.
adverse health effect of continuous exposure of students and teachers to heavy metals in the schools’
drinking water was determined. Within the school environment, the major human exposure risk
pathway the students are susceptible to is via direct ingestion. The method used was adapted from
the USEPA Risk Assessment Guidance for Superfund (RAGS) (US Epa 1989). The exposure dose
via oral ingestion of water was calculated using equation 1. The ingestion volume by the students
and adult staff during school hours was estimated to be 1 L (equivalent to two local sachet water)
and 1.5 L (equivalent to three local sachet water) respectively (Apeh 2018; Sanni 2019). The
reference weight (46.2 kg) of the students was obtained from literature (Akinpelu et al. 2009),
whereas the exposure frequency of the students was also estimated via the number of days spent in
school within the Lagos State every academic year (Lagos State Ministry of Education 2019). For
non-carcinogenic exposure, only the exposure duration within the school environment was con-
sidered (6 years for the school student and 30 years for the teachers as stipulated by the
Government), however for the carcinogenic exposure the estimated lifetime of the general popula-
tion was considered because the dose estimate is spread across a person’s life expectancy (USEPA
1999, 2005; EPA 2015).
Exping ¼ ðCwater IR EF EDÞ ðBW ATÞ(Equation1)
Where, Exping: exposure dose through ingestion of water (mg/kg/day); Cwater: concentration of heavy
metals estimated in
groundwater (μg/l); IR: ingestion rate (1.5 L/day for adults and 1 L/day for the students); BW:
average weight (70 kg for adults and 46.2 kg for children). The parameters specific for the
estimation of
Exping
for non-carcinogenic risk were – EF: exposure frequency (190 days) ED:
exposure duration (30 years for adults and 6 years for children); AT: averaging time (190 days/
year × 30 years for an adult and 190 days/year × 6 years for a student). While the parameters used to
estimate
Exping
for carcinogenic risk were – EF: 3665 days; ED (78 years for all both students and
teachers); AT: averaging time (365 days × 78 years) (US Epa 1989; Akinpelu et al. 2009; Li and
Zhang 2010; Edokpayi et al. 2018; Lagos State Ministry of Education 2019).
The non-carcinogenic risks were estimated using hazard quotients (HQ) and hazard index (HI)
using equations (2) and (3) respectively, this was also adapted from the US EPA guidelines (US Epa
1989). HQ values less than 1 is presumably non-carcinogenic and safe to the consumers, whereas
HQ value over 1 is suggested to pose a serious health risk (EPA 2015; Farokhneshat et al. 2016). The
composite potential of non-carcinogenic effect posed by several metals expressed as HI, was
determined by summing up the estimated HQ values for each metal. HI value greater than 1 also
suggests the respondents health could be put at risk due to continuous exposure to the pollutants
(US Epa 1989; Li and Zhang 2010; Naveedullah et al. 2014). However, since only one route of
exposure (ingestion by water) out of the four exposure routes (ingestion by water, ingestion by soil,
dermal contact, and inhalation) was considered in this survey, the threshold for HQ and HI were set
at 0.25. This implies that at levels beyond the threshold continuous exposure to the borehole water
could potentially affect the students’ and teachers’ health negatively.
HQing ¼Exping RfDing (Equation2)
n
HIing ¼X
n
i¼1
HQing (Equation3)
Where, HQ
ing
: hazard quotient via ingestion; RfD
ing
: ingestion reference dose (μg/kg/day); HI
ing
: Hazard index via ingestion.
RfD
ing
values used were derived from past studies: Pb – 1.4, Cr – 3, Fe – 700 and Cd – 0.5 (US
Epa 1989
;
Li and Zhang
2010
;
Edokpayi et al. 2018
).
Carcinogenic risk assessment via ingestion route was also determined using equation (4).
Carcinogenic risk is the likelihood a person would develop cancer due to long-term exposure to
one or more contaminants (USEPA 1999).
This was estimated by using a cancer slope factor (SF
ing
) to estimate the
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 5
probability of an individual
developing cancer as a result of long-term exposure to certain carcinogens
using the equation (Kolluru et al. 1996; USEPA 1999; Wongsasuluk et al. 2014; Farokhneshat et al.
2016):
CRing ¼Exping SFing (Equation4)
Where CR
ing
is the carcinogenic risk via ingestion and SF
ing
is the cancer slope factor for the heavy
metals. The SF
ing
for the heavy metals of interest were Pb−8.5 μg/kg/day, Cd−6.1×103 μg/kg/day
and Cr – 5.0 × 102 μg/kg/day (US Epa 1989; USEPA 2005; Iqbal and Shah 2013). Past studies have
revealed that CR
ing
values that ranging 10−6 to 10−4 could be tolerable (USEPA 1999, 2005;
Naveedullah et al. 2014). For this study, the threshold for carcinogenic risk was set at 10−5, thus
implying that exposures to higher levels of heavy metal puts the consumers at a carcinogenic risk.
Ethical consideration
Prior to the commencement of the survey, ethical approval was obtained from the University of
Ibadan/UCH Research Ethic Committee. Approval to also gain access into the selected schools was
obtained from the Lagos State Government through the State Ministry of Education, Alausa.
Results
Majority (80%) of the schools visited had drinking water sources. All (100%) the public schools and
60% of the private schools had boreholes in the school premises, with the water pumped directly
into a storage tank. The remaining private schools (40%) had no drinking water source. The
groundwater in all the schools with available drinking water source was withdrawn via electric
pumps in the boreholes, then distributed to storage tanks which supplied water to the end-users
through standpoint taps.
Of all the schools with drinking water sources, 100% of the public schools had water available
during the survey, whereas only 67% of the private schools had water available. Furthermore, it was
observed that all the public schools used solar panel systems as the power source for the water
pump, whereas all the private schools depended on generators and local power supply.
Number/proportion of functional taps available to serve the students
It was found that there were 15 drinking water taps available in the five government-owned school
(mean = 3 taps/school). Of the 15 taps, only 67% (10) were functional. Meanwhile, all the available
taps (3) in the three private schools were functional.
The student to functional tap ratio for the schools was estimated as seen in Table 1, the ratio for
the government school was 604 students to 1 tap and 219 students to 1 tap for the private school.
Table 1. Student to functional tap ratio across all schools with drinking water source.
School type School Total taps Functional taps Student population Student to Tap ratio Total Student to Tap ratio
Public Schools A1 3 2 756 378: 1 640
students to 1tapA2 1 0 21,668 21,668: 0
A3 4 2 1335 668: 1
A4 4 4 1037 259: 4
A5 4 2 1107 554: 1
Private Schools B1*0 0 182 182: 0 219 students to 1 tap
B2 1 1 210 210: 1
B3*0 0 251 251: 0
B4 1 1 260 260: 1
B5 1 1 188 188: 1
6E. O. OLORUNTOBA ET AL.
None (0%) of the schools had facilities like ramps, grab bars and low taps available around their
drinking water facilities to enable access to students having one or more forms of disabilities.
Drinking water quality analysis
The details of the results are shown in Table 2. The pH was the only physico-chemical not within the
WHO and SON permissible limits. All the schools had at least one heavy metal exceeding the SON
and WHO permissible limits. Both the public and private schools had E. Coli counts beyond
permissible limits.
Total coliform was detected in 7 (87.5%) of the water samples collected. However, only 2 (25%)
of the samples had total coliform detected at a level that exceeds the WHO and SON permissible
limit of 10. E. Coli was detected in 5 (62.5%) of the water samples collected from the schools in
Badagry LGA. The WHO and SON require that drinking water should be void of E. Coli. The
highest level of E.coli count detected was 1900 whereas the lowest was 1.
Sanitary inspection of water sources
Using a WHO recommended sanitary inspection form, the potential risk of contamination was
assessed. Table 3 provides details of the potential sources of contamination identified.
Table 2. Comparison of water quality parameters between public and private schools.
Parameters
Public Schools
Mean±SD
Private Schools
Mean±SD Min. Max. WHO Guideline SON Guideline
pH 5.49 ± 0.97aa 5.82 ± 0.36aa 4.11 6.77 6.5–8.5 6.5–8.5
Conductivity (µS/cm) 97.40 ± 84.04 139.67 ± 101.03 32 256 1000 1000
TDS (mg/l) 50.80 ± 46.62 69.33 ± 49.24 11 128 500 500
Chloride(mg/l) 21.00 ± 8.63 24.00 ± 7.81 13 35 NGV 250
Total Hardness (mg/l) 28.40 ± 4.16 27.33 ± 6.11 22 34 NGV 150
Salinity (mg/l) 35.95 ± 12.06 43.36 ± 14.11 23.48 54.2 NGV NGV
Nitrate (mg/l) 0.66 ± 1.44 0.01 ± 0.01 0.006 3.24 50 50
Pb (mg/l) 0.31 ± 0.05aa 0.0077 ± 0.01 0.000 0.097 0.01 0.01
Cr (mg/l) 0.75 ± 0.61aa 1.72 ± 0.38aa 0.012 1.845 0.05 0.05
Fe (mg/l) 0.028 ± 0.06 0.00 ± 0.00 0.000 0.142 NGV 0.3
Cd (mg/l) 0.046 ± 0.04aa 0.025 ± 0.02aa 0.000 0.080 0.003 0.003
Total Coliform count 482.80 ± 1071.76a 2.33 ± 0.58 0 2400 10 10
E. Coli count 381.00 ± 849.15aa 0.67 ± 0.58aa 0 1900 0 0
aParameter outside SON guidelines only **Parameter outside both SON and WHO guidelines NGV – No Guideline Value
Table 3. Point sources of groundwater (borehole) contamination.
Potential Point Sources of Contamination
Number of Boreholes
Affected
(N = 8)
Percentage of Boreholes
Affected
(%)
Presence of a latrine or sewer within 100 m of
pumphouse
8 100
Nearest latrine unsewered 0 0
Presence of other sources of pollution within 50 m 2 25
Presence of an uncapped well within 100 m 1 12.5
Faulty or no drainage around pumphouse 8 100
Damaged fencing allowing animal entry 1 12.5
Floor of pumphouse permeable to water 5 62.5
Presence of pool of water around the pumphouse 1 12.5
Unsanitary/worn-out borehole seal 2 25
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 7
Correlation between selected water quality parameters
The correlation between physiochemical parameters and bacteriological parameters were mea-
sured, the correlations between all the parameters are shown in the correlation matrix in Table 4.
The following variables had statistically significant correlations:
pH: This parameter had statistically significant correlations with nitrate, total coliform, and
E. coli count. There was a strong negative correlation between pH and nitrate (R = −0.781,
p < 0.022), total coliform (R = −0.781, p < 0.022) and fecal coliform (R = −0.782, p < 0.022).
Therefore, the pH level decreases significantly with increasing levels of nitrate, total coliform, and
fecal coliform.
Conductivity: The electrical conductivity of water had statistically significant correlations with
total dissolved solid, chloride and salinity. There was a strong positive correlation between pH and
total dissolved solid (R = 0.996, p < 0.000), chloride (R = 0.861, p < 0.006) and salinity (R = 0.846,
p < 0.008). Therefore, as the conductivity level increases, the levels of total dissolved solid, chloride
and salinity significantly increases too.
Nitrate: Nitrate had a perfectly positive correlation with both total coliform and fecal coliform
(R = 1.000, p < 0.000). This implies that for any significant increase in the nitrate levels, there is
a simultaneous significant increase in the level of total coliform and fecal coliform.
Heavy metals: There was a negative correlation between all the heavy metals and the coliform
count. The strongest negative correlation was between cadmium and coliform; for total coliform
r = −0.628 and p value = 0.096 whereas for fecal coliform r = −0.627 and p value = 0.096. Chromium
had a moderate negative correlation with coliform bacteria, whereas iron and lead had a weak
correlation with coliform bacteria. However, none of the associations were statistically significant.
Correlation of the distance between each water source to the Atlantic Ocean and the
salinity/chloride content of the groundwater
The correlation between the distance of each school’s water source to the Atlantic Ocean and level
of chloride/salinity in the groundwater was measured. There is a strong negative correlation
between the distance of each school’s water source to the Atlantic Ocean and level of chloride in
the groundwater (R = −729, p < 0.040) and the salinity in the groundwater (R = −0.772,
p < 0.025).
The linear regression between the distance between the water source to the Atlantic Ocean and
the salinity was also determined. The distances of the water source to the Atlantic Ocean was the
predictor variable and the salinity level was the outcome variable. A p value of 0.025 was obtained
for the regression model indicating that this model is statistically significant, implying that the level
of salinity in Badagry LGA ground water was based on the distance of the water source to the ocean.
The regression equation derived was given as:
Salinity of groundwater (mg/l) = 57.665 + (– 2.795) × (Distance of water source to the ocean)
Intercept = 57.665 and Regression coefficient (slope) = −2.795
Quantitative health risk assessment
Table 5 reveals the non-carcinogenic health risk assessment of the heavy metals of interest in the
groundwater samples obtained from public and private schools in Badagry coastal community. The
risk was assessed for both school students and adult staff (e.g schoolteachers, cleaners) via the oral
ingestion route only. The schools surveyed were day schools – they lack bathrooms and wash-
rooms – thereby limiting dermal and inhalation exposure.
8E. O. OLORUNTOBA ET AL.
Table 4. Correlation matrix for drinking water quality parameters.
pH Ec Tds Cl TH Nacl No Pb Fe Cr Cd TC FC DO
pH r
p value
1 0.545
0.162
0.572
0.138
0.573
0.138
0.010
0.982
0.505
0.201
−0.781a
0.022
0.200
0.635
0.135
0.750
0.252
0.547
0.305
0.463
−0.781a
0.022
−0.782a
0.022
−0.347
0.399
Ec r
p value
1 0.996b
0.000
0.861b
0.006
0.473
0.237
0.846b
0.006
−0.374
0.361
−0.100
0.814
−0.048
0.910
0.261
0.532
0.114
0.789
−0.374
0.361
−0.375
0.360
−0.648
0.082
Tds r
p value
1 0.878b
0.004
0.454
0.259
0.848b
0.008
−0.363
0.376
−0.053
0.901
−0.070
0.870
0.208
0.621
0.112
0.792
−0.363
0.376
−0.363
0.375
−0.630
0.094
Cl r
p value
1 0.210
0.618
0.981b
0.000
−0.363
0.376
0.011
0.979
−0.006
0.988
0.276
0.508
−0.054
0.899
−0.362
0.379
−0.363
0.377
−0.729a
0.040
TH r
p value
1 0.209
0.619
0.179
0.672
−0.098
0.818
0.442
0.272
−0.354
0.390
0.592
0.122
0.177
0.675
0.177
0.675
−0.194
0.645
Nacl r
p value
1 −0.377
0.357
−0.087
0.838
0.033
0.938
0.411
0.311
−0.092
0.828
−0.376
0.359
−0.377
0.358
−0.772a
0.025
No r
p value
1 −0.248
0.554
−0.143
0.735
−0.627
0.096
−0.364
0.375
1.000a
0.000
1.000b
0.000
0.320
0.439
Pb r
p value
1 −0.247
0.555
−0.343
0.405
0.485
0.223
−0.246
0.558
−0.246
0.556
0.478
0.321
Fe r
p value
1 −0.049
0.908
0.543
0.164
−0.144
0.733
−0.143
0.735
−0.432
0.285
Cr r
p value
1 −0.285
0.494
−0.628
0.096
−0.627
0.096
−0.442
0.273
Cd r
p value
1 −0.365
0.374
−0.365
0.374
0.088
0.835
TC r
p value
1 1.000b
0.000
0.320
0.440
FC r
p value
1 0.320
0.440
DO r
p value
1
aCorrelation is significant at the 0.05 level
bCorrelation is significant at the 0.01 level
Ec: electrical conductivity, Tds: total dissolved solid, Cl
−
: Chloride, TH: total hardness, Nacl: Salinity,NO3
−
: Nitrate, TC: total coliform, FC: Fecal coliform, DO: distance of water source from the Atlantic
Ocean
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 9
From the results obtained, it was observed that the hazard quotient via ingestion (HQi
ng
) for each
of the heavy metals were less than 1. This signified that the heavy metals present were not likely to
subject the consumers to any non-carcinogenic health risk. The HQ
ing
of the heavy metals increased
in the order of Feb<Cd<Cr, implying that Cr potentially posed the greatest risk via ingestion. The
health hazard indices (HI) also indicated that the cumulative exposure to the heavy metals via
ingestion was unlikely to pose any health risk, as the HI
ing
values were also less than 1.
Table 6 reveals the carcinogenic risks (Cr) posed to the students and adult staff because of oral
ingestion of heavy metals present in the drinking water sources. The results revealed that both Pb
and Cr had values above the permissible limit of 10
−6
among students and teachers in both the
private and public schools. This implies that there is a likelihood the students and adult staff would
develop cancer during their lifetime due to their exposure Pb and Cr via oral ingestion (Wu et al.
2009).
JMP Classication for school drinking water in Badagry LGA
Majority (80%) of the schools made use of boreholes as their source of drinking water, whereas 20%
had no source available at school. Of the schools with drinking water sources, majority (70%) were
classified as an improved drinking water source, 10% classified as having unimproved water source
and 20% with no water source. Majority (60%) of schools provided basic drinking water service,
30% provided no service and 10% provided limited service.
Storm water management
None (0%) of the schools had drainages for collecting wastewater or run-off. Episodes of ponding
was apparent in schools visited on raining days, such schools had water logged grounds. Majority
(70%) of the schools visited had areas with stagnant water, as a result of the water logged grounds
due to rain and accumulation of water on the grounds around the taps due to no drainage. The
Table 5. Health risk assessment (non-carcinogenic risk) for heavy metals in drinking groundwater (borehole) samples from public
and private secondary schools via oral ingestion for students and adult.
Heavy Metals
RfD
ing
μg/kg/day Range Public schools Private Schools
Students Adults Students Adults
HQ
ing
HQ
ing
HQ
ing
HQ
ing
Pb 1.4 Maximum Minimum 1.50E-03
0E-07
1.48E-03
0 E-07
3.56E-04
0E-07
3.53E-04
0 E-07
Cr 3 Maximum
Minimum
1.17E-02
8.66 E-05
1.16E-02
4.29 E-04
1.46 E-02
8.57 E-05
1.44 E-02
9.19 E-03
Fe 700 Maximum Minimum 4.40 E-06 0 E-07 4.30 E-06 0 E-07 0 E-07
0 E-07
0E-07
0 E-07
Cd 0.5 Maximum
Minimum
3.46 E-03
4.33 E-04
3.42 E-03
2.14 E-03
1.95 E-03
0 E-07
1.93 E-03
0 E-07
HI
ing - Maximum Minimum 1.67 E-02
5.20 E-04
1.65 E-02
2.22 E-03
1.69 E-02
9.28 E-03
1.67 E-02 9.19E-03
Table 6. Carcinogenic risk assessment (CRing) for heavy metals in drinking groundwater samples (boreholes) from public and
private secondary schools in Badagry coastal communities for students and adults.
Metal Public schools Private Schools
Students Adults Students Adults
Pb 0E-07 to 2.47E-04*0E-07 to 2.44E-04*0E-07 to 5.86E-05 0E-07 to 5.80E-05
Cr 5.2E-7 to 7.02E-05 5.14E-7 to 6.95E-05 5.57E-05 to 8.74E-05 5.51E-5 to 8.65E-05
Cd 3.5E-08 to 2.8E-07 2.8E-07 to 3.5E-08 0E-07 to 1.60E-06 0E-07 to 1.58E-07
*Values that exceed the acceptable 10
−5
limit
Adults include teachers, cleaners, security personnel and other school staff
10 E. O. OLORUNTOBA ET AL.
schools that were without stagnant water on school grounds had two similarities: firstly, they had
their taps well-constructed to avoid accumulation of water and secondly, they were visited around
periods when it was not raining.
Discussion
Availability of drinking water sources
Majority (80%) of the schools had a functional drinking water source, a borehole within the school
premises. This is most likely because the water Table 1 n the coastal community is relatively shallow
compared to the mainland regions, so the cost of drilling a borehole would be way cheaper as the
cost of drilling a borehole in Nigeria is to a great extent dependent on the depth (Oyebode et al.
2015). A water quality survey around the study area estimated the mean depths of hand dug wells in
the area to be 2.99 m (Balogun et al. 2012). The presence of boreholes in most of the schools also
backs the claim that borehole water is the most common source of improved water in Nigeria (Ndhs
2013). Generally, in Lagos State, only a-tenth of the population receives water from the State water
corporation, whereas majority depends on private boreholes and water vendors (Jideonwo 2014).
The status of water facilities here is clearly an improvement from a WASH assessment carried
out in 2013 among public schools in Southwestern Nigeria (Lagos, Abeokuta, and Ota), where only
25% of the schools had drinking water points (Olukanni 2013). Furthermore, a WASH survey
conducted in an urban slum in Lagos reported that none of the schools in the community had
sources of drinking water supply (Babalobi 2013). Another assessment carried out across secondary
schools in Anambra, Ekiti, and Kastina States revealed that only 50% of the schools had a functional
water source at school (UNICEF 2015b). The comparative improvement in the study area with
water supply could be credited to strong political will by the State Government.
In addition, the availability of water in all the public schools at the time of the survey as opposed
to just 67% of the private schools with a drinking water source is most likely because all the
government – owned schools powered their water pumps with solar energy via solar panels
provided by the government. However, all the private schools depended on generators and local
power supply. The availability of renewable energy made the water project in the public schools
more sustainable, as it did not depend on the local erratic power supply or funds for fuel. Solar
systems have been proven to be an economical way to provide electricity in remote locations,
because it can be more affordable than installing power grids and transformers (Eker 2005).
There were disparities observed between the public and private schools upon assessing the
maintenance of the water supply facilities. Of all the schools with a drinking water source, none
of the private schools had their drinking storage containers uncovered, whereas 40% of the public
schools had uncovered tanks. All the drinking water taps present in the private schools were
functional, whereas 33% of the drinking water taps present in the government schools were not
functional. The poor maintenance culture commonly practiced by government institutions in
Nigeria has been regarded as a bane to national development (Tijani et al. 2016). The provision
of a specialized budget for the maintenance of WASH facilities has been recommended as a solution
(Alexander et al. 2016).
A high rate of open defecation (35.4%) and absence of basic handwash services in these schools
have been reported by past literature (Wada et al. 2020; Wada and Oloruntoba 2021). The practical
implication of these findings is that with over 600 public students having access to just 1 tap, the
chances of cross-contamination of germs via the tap knobs increases significantly. Frequently touch
surfaces have been reported to act as a reservoir for infectious pathogen, thereby aiding disease
transmission (Pittet et al. 2006; Huslage et al. 2010). Moreover, the unavailability of facilities like
ramps, grab bars and low tap in all the schools mean the water facilities were not socially inclusive
for disable children. This would most probably discourage disable students in that locality from
attending the academic institutions (UNICEF 2012).
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 11
Quality of drinking water
The saline levels in the groundwater samples revealed that the coastal community was not subjected
to saline intrusion, the peak salinity value was at 54.20 mg/l. Literature has revealed that saline-
water has the tendency to settle beneath the coastal aquifer whereas fresh water remains above due
to the density and pressure of salt water (NGWA 2019). A research recently conducted around the
study area indicated that aquifers in Badagry LGA are majorly characterized with freshwater; saline-
water intrusion was observed at a depth between 120 m and 155 m (Bayode 2018). Compared to
other coastal regions of Lagos, the study area has been reported to have very low municipal
residence and commercial activity, as well as virtually no industrial activities, therefore keeping
the freshwater abstraction relatively low compared to areas like Apapa and Lekki (Oloruntola et al.
2019).
The presence of slightly acidic pH in majority of the water samples was also reported by
(Oloruntola et al. 2019), where 87.3% of the samples were slightly acidic and by Akoteyon et al.
(Akoteyon et al. 2018), where as high as 95.6% of a sampling site had acidic pH. As opposed to
a study by Subba et al. ((Subba Rao et al. 2005)), where majority (95.0%) of the groundwater
samples collected from a coastal area in Visakhapatnam were classified as being hard, all of the
groundwater samples collected from Badagry coastal community were soft. Another survey around
the study area also reported that 93.3% of the samples were soft (Akoteyon et al. 2018). The major
factors reported to be responsible for the groundwater hardness in Visakhapatnam coastal com-
munity were the over – exploitation of groundwater and the industrial activities carried out in the
area.
High heavy metal concentration of parameters like lead, chromium, and cadmium in the water
samples was alarming. WHO has reported that presence of chemicals like lead, chromium and
cadmium in children’s blood beyond recommended limits could result in dullness, irritability,
abdominal cramps and kidney damage (WHO 2004). Long-term consumption of chemical
pollutants like lead in water can impair learning and cognitive ability of children (Adams). The
EPA and CDC have reported that there is no known safe level of lead in a child’s blood. Even at
low levels of exposure, lead has been reported to affect the development of the brain and nervous
system (WHO 2011). Unfortunately, these contaminants do not impact on the color, turbidity,
and palatability of the drinking water. This makes it difficult for the students and teachers to
know they are consuming polluted water, which show why it is essential for routine testing to be
done by the necessary authorities. Compared to adults, children are more liable to suffer the
harmful effects because of consuming water with chemical contaminants (WHO Regional Office
for Europe, European Environment Agency (EEA) 2002). Other studies assessing for ground-
water quality in Lagos has also reported elevated heavy metal concentrations of lead, iron,
cadmium, and manganese (Oluyemi et al. 2009; Ehi-Eromosele and Okiei 2012; Ogbuneke and
Ezeibeanu 2020).
Majority (63%) of the drinking water was classified as unsatisfactory because of the presence of
fecal coliform. Waterborne transmission of pathogenic E. coli has been well documented for
recreational waters and contaminated drinking-water (WHO 2017). The detection of coliform in
groundwater indicates a source of fecal pollution in proximity. One of the probable sources of total
coliform and E.coli in the groundwater are the septic tanks, some were in close proximity to the
water sources. The safe distance between the groundwater and the septic tank has been suggested to
be at least 10 m or 30 m depending on the nature of the environment (Wade 2005; Harvey 2007).
However, the average distance of the nearest septic tanks to the water sources across the schools was
30.5 m. Over 60% of the water sources had distances less than 22 m to their respective nearest septic
tank. The negative impact of the lack of safe distance was clearly seen at water source A2, where the
distance was barely 4 m, resulting in extremely high levels of total coliform and E.coli (2400 counts
and 1900 counts, respectively).
12 E. O. OLORUNTOBA ET AL.
The overall quality of the drinking water samples were most probably affected by their close
proximity to septic tanks, run-off from school solid waste dumpsites, absence of drainage around
the pumphouse, permeable floor around the pumphouse and presence of unsanitary borehole seal.
These sources of contamination were identified via the sanitary inspection. Even though there are
guidelines set by the SON to ensure the quality of drinking water within Nigeria is within
recommended limit, there are no strict monitoring and enforcement measures put in place.
Therefore, the quality of water is mostly poor (Ighalo and Adeniyi 2020).
Quantitative health risk assessment
The heavy metals in the drinking water samples were not likely to pose any non-carcinogenic threat
to the students and adult staffs, as the HQ and HI values were below the permissible limit (US Epa
1989; Li and Zhang 2010; Naveedullah et al. 2014). Similar results were obtained in a similar survey
that examined groundwater in Muledane, South Africa (Edokpayi et al. 2018) and in a survey that
assessed groundwater and surface water around Bosomtwe Crater Lake in Ghana (Asare-Donkor
et al. 2016). Another survey similarly assessing the human health risk of heavy metals contamina-
tion of groundwater in East Algeria had an opposing result. Cd and Pb had their HQing values >1,
thereby putting the consumers at potential non-carcinogenic health risk. A mean HIing value of
6.48 was also derived, further proving that the inhabitants were susceptible to non-carcinogenic
health risk (Belkhiri et al. 2018). The carcinogenic risk posed by the levels of Pb has also been
reported in other studies (Asare-Donkor et al. 2016; Edokpayi et al. 2018; Ukah et al. 2019). This
situation becomes more bothersome if the carcinogenic risk threshold is reduced to 10
−4
as seen in
some other surveys, which would imply that even the estimated Cr levels could pose a carcinogenic
risk to the consumers (Iqbal and Shah 2013). The potential carcinogenic risk posed by the heavy
metals in the drinking water sources further stresses the importance of routine testing and manage-
ment of water sources/bodies for heavy metal pollution.
JMP ladder for drinking water for senior secondary schools in Badagry LGA
With most (60%) of the schools having basic service, 30% having no service and 10% having limited
service, the result is similar to the global WASH in school service classifications where 69% of
schools had basic drinking water service, 12% had limited service and 19% with no service (Steele
2018). The result is however better than the Sub-Saharan Africa (SSA) ratings where less than half
were recorded to have no drinking water service (Steele 2018). The availability of water supply in
schools in this rural-like costal community is above the national rate, which reported that 51% of
the rural areas in Nigeria did not have access to improved water (World Bank 2017). This implies
some sort of progress in this area; however, it should be improved upon and adequate maintenance
measures need to be put in place.
Storm water management
The lack of drainages in all the schools gives room for pools stagnant water, especially after it rains.
With the study area being a coastal community, the rainfall in the area is more intense and the
raining season is relatively longer than other landlocked regions. The transmission of water-related
vector-borne diseases like malaria, lymphatic filariasis and schistosomiasis has been closely asso-
ciated the presence of excess water (due to inadequate drainage) in the tropical and subtropical
regions (Food and Agriculture Organization of the United Nations (FAO) 2001). Lack of adequate
drainage structures have also been reported to lead to flooding, which results into immediate loss of
life and the damage of properties. The damages caused by flood episodes across Nigeria in the year
2012 were estimated to cost about 2.6 trillion Naira (RusselSmith 2016). A survey conducted to
assess the drainage systems in Lagos State revealed that the facilities available were mostly
INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 13
inadequate, thereby routinely predisposing the residents to flooding during rainy seasons
(Aderogba et al. 2012). Another survey conducted in Lagos reported the drainage systems were
grossly inadequate and that the residents were susceptible to outbreaks of waterborne diseases
(Olukanni et al. 2014). A research carried out to determine the water-borne disease in coastal
communities in Sri Lanka revealed that diseases like shigellosis, cholera, hepatitis A and E and
typhoid fever were prominent in the area due to the contamination of water by improper drainage
management, adding effluents with the water source, over population and the deficiency of the
awareness among residents about water-borne diseases (Fowsul 2017).
Conclusion
It was noteworthy that all the public schools had water sources that provided water round-the-clock
due to the use of solar panels. However, this progress was marred by the absence of water sources in
40% of the private schools and the contamination of majority of all the water sources with heavy
metals and fecal bacteria. The absence of structured drainages in all the coastal schools was also
a major point of concern. This clearly signifies the students in Badagry community would be at
a constant health risk if the situation is not remediated. The current condition creates an enabling
environment for waterborne and water-related diseases like cholera, typhoid, diarrhea, giardia,
hepatitis A and malaria to thrive. Moreover, the heavy metal contamination of majority of the water
sources also poses a cancer risk to the consumers.
Recommendation
(1) Subsequent interventions must ensure that proper environmental surveys are conducted
before the boreholes are dug. The proximity of some of the water sources to septic tanks
indicated that no proper assessment was conducted before the project was implemented.
(2) Point sources of pollution such as septic tanks, dumpsites, and pumphouse with permeable
floors need to be identified and effectively managed. This would help improve the ground-
water quality.
(3) The local authorities should ensure the private schools also make provision of drinking
water a priority, as 40% of the private schools lacked a drinking water source.
(4) All the private schools should also be encouraged to install solar powered water pumps like
the public schools. This would guarantee the availability of water round-the-clock as
witnessed in the public schools.
(5) The public schools need to setup and implement sustainable maintenance mechanism to
ensure the water services are optimal per time. Such schemes would help improve the
average students to tap ratio which stood at 604:1 for the government schools.
(6) Subsequent water projects should also be socially inclusive to improve the overall accessi-
bility to students with one or more forms of disabilities.
(7) The drinking water sources should be routinely tested by local authorities.
(8) Measures to mitigate the microbial and heavy metal contamination of groundwater need to
be put in place if subsequent water quality assessment reveals similar results. Filters and
disinfectants could be introduced as a mitigating measure for the heavy metal and micro-
bial contamination, respectively.
(9) Routine checks to ensure the storage tanks are always covered and to ensure that they are
washed at intervals are also important mitigating measures to put in place.
(10) Adequate drainage channels need to be constructed in all the Badagry community schools.
14 E. O. OLORUNTOBA ET AL.
Acknowledgement(s)
Open Access funding provided by the Qatar National Library.
Disclosure of potential conicts of interest
None was declared by the authors.
Data availability statement
Data available on request due to privacy/ethical restrictions.
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