Assessment of Heavy Metals Contamination in Groundwater and Its Implications for Public Health Education: A Case Study of an Industrial Area in Southwestern Nigeria

Abstract

Heavy metals’ presence in groundwater has garnered a lot of attention recently due to their impact on ecosystem and human health. Thus, this chapter was designed to assess the effects of heavy metals contamination in groundwater and its implication for public health education in selected communities located in an industrial area in Ogun state, southwestern Nigeria. Fifty groundwater sources were identified using a handheld global positioning system and analyzed for physicochemical and heavy metals properties. Four-hundred participants were selected and interviewed using pre-tested semi-structured questionnaire. The results indicated that there were high quantities of heavy metals in the groundwater that were above the allowable limit set by national and international regulations. A larger percentage of the respondents’ drinks water from groundwater supply. The majority of those surveyed were poorly informed on the effects of heavy metal contamination. The following ailments were experienced by the respondents in the last 6 months: frequent watery stool, difficulty in breathing, and skin infection. Few of the respondents reported the following occurrences in their household in the last 1 year: still birth, stunted growth in child, and death due to cancer. Therefore, there is a requirement for immediate public health education and health promotion activities among the local populace.

1. Introduction

Human life depends critically on water. For the survival of all living things, it is absolutely essential. The best source of freshwater with the smallest amount of salts for human consumption is groundwater [1]. Unchecked population explosion, uncontrolled urbanization, and inappropriate disposal of solid and liquid wastes all contribute to the intrusion of hazardous materials into underground water supplies [2]. The two main causes of groundwater pollution are the unregulated discharge of industrial wastes and the use of chemical fertilizers in agriculture [3]. The increased use of water by people, particularly as a receptacle to dispose of human waste, is another important factor contributing to groundwater pollution. The impacts of additional organic matter and pathogens are of public health significance [4, 5]. Additionally, because of the soil’s porosity, sewage, and leachate from wastes are more likely to enter subsurface water bodies, which are an important supply of water for many towns [6]. Water-borne infections have created a significant epidemic of sickness as a result of fecal waste contamination of drinking water [7, 8].

One of the main pollutants in groundwater sources is heavy metals [9]. Some of these heavy metals are necessary for an organism’s growth, development, and health, whereas others are not since they are irreplaceable and the majority of them are harmful to living things [10]. But the concentration of heavy metals in the environment determines how harmful they are. Heavy metals leach into groundwater and soil solution as ambient concentrations rise and soils lose their capacity to retain them. These dangerous heavy metals can consequently accumulate in living tissues and concentrate at the top of the food chain [11]. Effects of heavy metals bioaccumulation at biochemical levels often include the replacement of required ions, harm to plasma membranes, interactions with sulfhydryl (-SH) groups, reactions with phosphate ions, and competition for binding sites with important metabolites [12, 13].

In Nigeria, boreholes and dug wells provide a significant portion of the country’s drinking water supply. Since groundwater is often the primary supply of drinking water in rural and some urban regions, a sizable population is at danger of ingesting contaminated water. Groundwater quality is influenced by a variety of factors, including aquifer lithology, groundwater velocity, the quality of recharge fluids, interactions with other types of water or aquifers, human activities, and the environment [14]. Environmental monitoring and impact assessment programs have attracted a surge of interest from planners and environmentalists concerned with the environmental repercussions of companies. Scott [15] asserts that there has been a tendency to neglect how industries in the developing countries affect the environment. Although the growth of these firms is regarded to be a way to increase employment and earnings, there is not enough information on their environmental impact and sustainability to support decision-making.

The industrial sectors in Shagamu and Otta are thought to be Ogun state’s fastest-growing areas, located in the southwestern part of Nigeria. Groundwater is largely one of the geological resources that have been negatively impacted by this expansion. When surface water supplies are no longer sufficient to satisfy the needs of communities, groundwater is the only other source of high-quality water. However, it has been shown that some regions of the industrial belts have a number of problems with groundwater contamination [14]. The conurbation of Shagamu and Otta has a sizable number of diverse industries, all of which have been developed. As a result, these industries have been dangerously degrading the quality of groundwater by releasing pollutants into the ambience at ever-increasing amounts. Hence the main objectives of this chapter are to: (1) characterize the physicochemical and heavy metal properties of groundwater collected from the selected communities in line with national and international permissible limits, (2) assess the knowledge level of households on toxicities associated with heavy metals contamination of groundwater, and (3) assess the health status of respondents’ households in the last six (6) months.

2. Methodology

In this section, we shall discussed the step by step methodology employed in the assessment of heavy metals contamination in groundwater; and the survey on the knowledge level and health implication of these contaminations among residents in the concerned areas. We shall begin with the study design and other baseline information; followed by the environmental sampling and laboratory analytical procedure; and end this section with cross-sectional descriptive survey.

2.1 Study design and baseline information

In order to accomplish the study’s stated aims, two (2) designs were used: a laboratory investigation and a cross-sectional descriptive survey. The study was conducted in Ogun State’s Shagamu Local Government Area (SLGA), which is in Nigeria’s southwest. On September 23, 1991, the former Remo Local Government was divided into the SLGA. Its borders are Odogbolu Local Government, Lagos State, Ikenne Local Government, and Obafemi Owode Local Government in that order. According to the 2006 census, it has a land area of 605.6 sq. km and a population of 255,885. According to the 2006 National Population Commission, the expected population in 2022 will be 435,200, growing at a rate of 3.4% year. The area is divided into fifteen (15) wards for administrative and political convenience, namely: Oko Epe and Itunla 1—I; Oko Epe and Itunla—II; Aiyegbami/Ijoku—III; Sabo 1—IV; Sabo 11—V; Itunsoku/Oyebajo—VI; Ijagba—VII; Latawa—VIII; Ode-lemo—IX; Ogijo/Ikosi—X; Surulere—XI; Isote—XII; Simawa—XIII; Agbowa—XIV; and Ibido/Itn Alara—XV. Due to the existence of several industries, indiscriminate waste disposal methods, and high industrial activity practices, Sabo1, Sabo 11, and Ogijo/Ikosi were chosen study sites [16].

2.2 Laboratory study

2.2.1 Environmental sampling (coordinates acquisition)

Using a GPS Garmin 60 on-site at the groundwater source location, samples were located. The GPS was activated and given authorization to use satellite signals for navigation. Following the receipt of full signals, the GPS device’s coordinates for the groundwater source were registered, downloaded, and inserted into the database to produce a map that shows the positions of the samples throughout the study area. In order to maintain track of each unique location, the way points were kept to correlate with the names of each groundwater supply site.

2.2.2 Sample collection and transport

Fifty groundwater samples were purposefully collected for laboratory analysis from the chosen study sites (Sabo1, Sabo 11, and Ogijo/Ikosi). Sterilized 500 ml bottles were used to collect the water samples. A portable GPS unit was used to find the groundwater locations (GPS). Using a multifunctional digital pH meter, the pH, temperature, TDS, and conductivity of the groundwater samples were promptly determined. Concentrated hydrogen trioxonitrite (IV) (HNO₃) was used to preserve water samples before they were sent directly to the lab for testing.

2.2.3 Physicochemical analysis of sample

The following physicochemical properties were assessed for in the collected water samples:

1. pH: Using a calibrated multifunctional conductivity, total dissolved solids (TDS), temperature, and pH meter, the pH values of the water samples were obtained (Hanna HI 9811-5 model). The pH meter probe was inserted into the sample containers. After the LCD display had stabilized, the pH readings were then taken.

2. Conductivity: The capacity of a substance to transport heat, electricity, or sound is referred to as its conductivity. Using a conductivity meter (Hanna HI 9811-5 model), the conductivity of the 50 water samples was determined. Once a constant number was obtained, the results were read.

3. Temperature: Water temperature is the degree Celsius reading of the water sample at the moment it was taken. The time of day and the current weather conditions both play a role. The rate of chemical reaction in the water accelerates as temperature rises. The multipurpose instrument (Hanna HI 9811-5 model) was used to determine the temperature of the samples. A 500 ml sterilized bottle was placed into the already switched-on meter, with the electrode tip touching the water. The outcome was read once a reliable reading had been acquired. The identical procedure was used to each of the 50 water samples.

4. Total dissolved solids (TDS): A measure of dissolved solids in an aqueous solution is called TDS. “Dispersed solids” refers to any minerals, salts, cations, or anions that have dissolved in water. TDS is made up of certain trace amounts of organic material as well as dissolved inorganic salts like calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates. TDS is a test that evaluates the overall water quality. Since the TDS content is more of an esthetic than a health concern, it is regulated as a secondary drinking water standard. Though it is not linear, there can be a correlation between a TDS content and water conductivity. The TDS of the 50 water samples was determined using a TDS/conductivity meter (Hanna HI 9811-5 model).

2.2.4 Heavy metals determination of samples

The Association of Analytical Chemists (AOAC) methodologies were used to determine the concentration of heavy metals in groundwater samples as outlined below:

2.2.4.1 Digestion of samples

After cleaning and drying the equipment, 10% aqua-regia (HCl, HNO₃ ratio: 3:1) was used to rinse it. In a clean, 250 ml conical flask, 5 ml of pure nitric acid (HNO₃), and 100 ml of the preserved sample were added. The mixture was cooked on a hot plate inside the fume cupboard until it was almost dry. A further addition of 10 ml of distilled deionized water and 1 ml of hydrogen peroxide was added. The digesting vessel was covered with a crucible and heated for a further 5 minutes. The digest was quantitatively transferred to a 50 ml volumetric flask after cooling, with the volume being made up with distilled deionized water. It was then labeled and analyzed for the parameter(s) of interest. The other samples and the blank were treated in the same way.

2.2.4.2 Determination of heavy metals concentrations (As, Cd, Cr, and Pb)

After digestion, the samples were tested for arsenic (As) at 193.7 nm, cadmium (Cd) at 228.8 nm, chromium (Cr) at 357.9 nm, and lead (Pb) at 283.3 nm using the Perking 3300 AAS. A Perkin Elmer MHS-10 hydride generator was utilized to measure the system’s As. The analytical conditions for the standard and blank assays for each metal were the same. The AAS readout, sample volume acquired for analysis, and extract volume were all used to compute the metal content in each sample.

$$\text{Metal}\left(\mathrm{mg}/\mathrm{L}\right)=\frac{(\text{The result}-\text{Blank})\times \mathrm{Vol}.\text{of extract}}{\mathrm{Vol}.\text{of Sample taken}}$$E1

Note: Both the physicochemical and heavy metals analyses results were compared with permissible values/limits specified by both International and local bodies vis World Health Organisation (WHO) [17], and Nigerian Standard for Drinking Water Quality (NSDWQ) [18].

2.3 Household survey (cross-sectional study)

2.3.1 Sample size determination

The number of households needed for the survey was determined using Leishie Kish formula.

$$\mathrm{N}=\frac{{\mathrm{Z}}^2\mathrm{P}\left(1-\mathrm{P}\right)}{{\mathrm{d}}^2}$$E2

where

1. N = Sample size

2. Z = The value of the normal variant, confidence level of 1.96 for the 95% confidence interval.

3. P = The expected prevalence rate (in this case being a new study, 50% prevalence was considered (0.5)).

4. d = The highest acceptable absolute precision in % (±5%) = 0.05 error in the estimate substituting the formula, given:

$$\mathrm{N}=\frac{{\left(1.96\right)}^2\times 0.5\left(1-0.5\right)}{{\left(0.5\right)}^2}$$E3

$$=\frac{3.84\times 0.5\left(0.5\right)}{0.0025}$$

$$=384\text{individuals}$$

This was rounded up to 400.

2.3.2 Sampling technique

A three stage multiple sampling process was used. From the local government area, 15 wards were identified. Three of the 15 wards were specifically chosen because of their heavy industrial activity and indiscriminate waste disposal. Seven communities were purposively selected from the three wards based on their high levels of industrial activity and careless waste disposal, both of which are risk factors for heavy metal poisoning of the environment. The systematic sampling method was used to choose households from among the seven communities. This entails picking a family at random, sampling every subsequent nth = 3rd house, that is, first, fourth, and seventh.

2.3.3 Instrument for data collection

The authors devised a structured, interviewer-administered questionnaire that was pretested for data collection. The survey was divided into four components, including:

Section A: socio-demographic information of the respondents. Section B: general information on water supply. Section C: assessed respondents’ knowledge level on heavy metals problems. Knowledge was scored based on seven (7) items with each correct answer attracting 1 mark. The total mark was 7, while the lowest score was 0. Respondents that scored between 0 and 2 were grouped under poor knowledge; those that scored between 3 and 5 were grouped under fair knowledge while those that score between 6 and 7 were regarded as having good knowledge. Section D: respondent’s information on health status. The questionnaires contained both open and close ended questions.

2.3.4 Validity and reliability of the instrument

The test-retest method was employed to evaluate reliability. This strategy entailed administering the same instrument to the same subjects on various occasions while operating under comparable assumptions. The results of multiple tests were compared. The questionnaire was distributed twice over the course of 2 weeks to 40 households representing 10% of the sample size in Odogunyan, Lagos State, which is about 1 km from the study area and is also susceptible to heavy metal contamination due to industrial activities and careless trash disposal. The questionnaire’s consistency was checked using the pre-testing. The reliability coefficient was calculated to assess the instrument’s dependability for the study and check for internal consistency of answer. The pre-reliability test’s value was 0.76, which demonstrated the validity of the questionnaire.

2.3.5 Data collection procedure

Face-to-face interviews were used to gather the data over the course of twelve (12) weeks.

2.3.6 Data management and analysis

After data collection, the questionnaires underwent a careful completion check. The data was manually entered and analyzed using IBM Statistical Product and Service Solutions version 23. The examined data were represented using descriptive statistics (mean and standard deviation), frequency tables, percentages, and charts.

2.3.7 Ethical consideration

The Babcock University Health Research Ethics Committee (BUHREC) accepted the protocol and gave the study its ethical approval. The study was conducted in compliance with the Helsinki Declaration. A letter of introduction to the Chairman of the Sagamu Local Government Area was acquired from the Department of Public Health prior to the start of the study. The communities were allowed admission after receiving a letter of approval from the local authorities. Additionally, before being enrolled in the study, all willing individuals verbally consented after being informed about the research. Those who agreed were thumb printed or signed before being questioned (for illiterate participants). The respondents were given the promise that the information they provided would be utilized only for research, and the researchers strictly protected the privacy and confidentiality rights of the study participants.

3. Results and discussion

This section deals with findings and discussions of the results obtained from the lab work and field survey. It presents the physicochemical properties and heavy metals analysis results of the water samples collected from the various sampling sites. It also highlights the findings from the socio-demographic characteristics, general information on water supply, and knowledge of respondents on the health impacts of heavy metals contamination. The results were presented using frequency tables, charts, line graphs, mean, and standard deviation.

3.1 Physicochemical properties of water samples

The findings of the physicochemical analyses of the groundwater samples are shown in Table 1 below, together with the permitted limitations for each parameter set by the World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ). The samples’ pH ranged between 3.8 and 7.9, with a mean value of 4.79 ± 1.6. The temperature had a mean of 30.09°C and a range of 27.7 to 34.5°C. A mean value of 81.25 ± 5.8 μ²/cm was obtained for the conductivity value, which ranged from 010 to 750 μ²/cm. With a mean value of 503.9 mg/L, the total dissolved solids (TDS) value ranged from 001 to 3360 mg/L.

Parameter	Range	Means/SD	WHO 2011/NSDWQ 2008
pH	3.8–7.9	4.794 ± 1.6	6.5–8.5
Temperature (°C)	27.7–34.5	30.093 ± 3.6	Ambient
Conductivity (μ^2/cm)	010–750	81.25 ± 5.8	500
Total dissolved solids (mg/L)	0010–0360	50 ± 3.9	500–600

Table 1.

Physicochemical properties of groundwater samples.

The pH of the sampled water was outside the range (6.5–8.5) specified by the WHO/NSDWQ. This result is an indication that the groundwater in the selected communities is acidic, which potent ill to the health and well-being of the populace who depend on it as their source of drinking water. This acidity may be attributed to the high industrial activities and emission of noxious gases such as CO₂, SO₂, and NO₃ which formed carbonic, sulfuric, and nitrous acid in the air; and later precipitates as weak acid during rainfall and infiltrate into the groundwater [14, 19]. Acidosis may result from consuming such samples of water on a regular basis because the pH is too low (acidic pH) [20]. Similar to this, acidic water has been linked to mucous membrane cell destruction and skin and eye discomfort [21]. This conforms to the findings of Longe and Balogun [22], who reported a 5.30–7.07 range in Lagos, Nigeria groundwater. The value’s proximity may be the result of geological comparison. The groundwater mean temperature value observed in this study was comparable to those reported by Ojekunle et al. [14] in Sango-Otta, Okareh et al. [19] in Shagamu, and by Rahim and Hussain [23] in an industrial area of India. All the authors found groundwater temperatures to range from 28 to 30°C.

Ions are detected in water by measuring its electrical conductivity (EC), a measure of total dissolved solids. Shagamu’s EC values ranged from 010 to 750 μ²/cm. This may be connected to the local lithology and predominate anthropogenic activities. Furthermore, this outcome is comparable to earlier work by Refs. [14, 19, 24]. The term “total dissolved solid” (TDS) refers to inorganic salts. The measured TDS values were within the limits of Standard Organisation of Nigeria (SON) [18] and World Health Organisation (WHO) [17] standards, which call for 500 and 600 mg/L, respectively. The range of the TDS values obtained in groundwater for the current investigation is less than 1000 mg/L, as shown in Table 1, and can therefore be categorized as freshwater [25, 26]. The outcome is consistent with related research by Refs. [19, 27].

3.2 Heavy metals concentrations in groundwater

The groundwater of the study area was analyzed for the presence of four heavy metals: As, Cd, Cr, and Pb. The varied heavy metal concentrations found in fifty (50) samples of groundwater are shown in Tables 2–5 and Figure 1. Arsenic (As) concentrations ranged from 0.0001 to 0.0089 mg/L, with a mean value of 0.002–0.002 mg/L. The levels of As in every source of water that was sampled are all below the WHO/NSDWQ-approved permitted limits. The minimum and maximum concentrations that were found were <0.0001 and 0.0089, respectively. With a mean concentration of 0.080.11, the cadmium (Cd) content ranges from 0.01 to 0.43 mg/L. Only 52% of the water sources that were analyzed had Cd concentrations that were within the permissible range outlined by WHO/NSDWQ. The minimum and maximum concentrations that were found were <0.01 and 0.43 mg/L, respectively. With a mean concentration of 0.03–0.05 mg/L, the value for the chromium (Cr) determination ranges from 0.001 to 0.215 mg/L. The WHO/NSDWQ maximum permissible level for Cr concentration is met by more than a third (78%) of the analyzed water sources. The minimum and maximum concentrations that were found were 0.001 and 0.215 mg/L, respectively. The concentration of lead (Pb) varied from 0.01 to 3.26 mg/L, with a mean of 0.51–0.71 mg/L. A few (12%) of the water sampled has Pb concentration within the WHO/NSDWQ permissible limit. The concentration ranges from 0.01 mg/L at the lowest level to 3.26 mg/L at the highest level.

Parameters	Borehole water	Well water	Both
Number of total samples	41	9	50
Number of arsenic detected within WHO/NSDWQ limit (MCL)	43	7	50
Percentage of arsenic detected within WHO/NSDWQ limit (MCL)	86%	14%	100%
Number of arsenic detected above WHO/NSDWQ limit (MCL)	0	0	0
Percentage of arsenic detected above WHO/NSDWQ limit (MCL)	0	0	0
Minimum concentration detected (mg/L)	<0.0001	0.0001	<0.0001
Maximum concentration detected (mg/L)	0.0089	0.00061	0.0089
WHO/NSDWQ maximum contaminant level (MCL) (mg/L)	0.01	0.01	0.01
Mean	0.002	0.002	0.002

Table 2.

Levels of arsenic concentration in groundwater samples.

Parameters	Borehole water	Well water	Both
Number of cadmium detected within WHO/NSDWQ limit (MCL)	19	7	26
Percentage of cadmium detected within WHO/NSDWQ limit (MCL)	38%	14%	52%
Number of cadmium detected above WHO/NSDWQ limit (MCL)	23	1	24
Percentage of cadmium detected above WHO/NSDWQ limit (MCL)	46%	2%	48%
Minimum concentration detected (mg/L)	<0.01	0.12	<0.01
Maximum concentration detected (mg/L)	0.43	0.12	0.43
WHO/NSDWQ MCL (mg/L)	0.003	0.003	0.003
Mean	0.08	0.08	0.08

Table 3.

Levels of cadmium concentration in groundwater samples.

Parameters	Borehole water	Well water	Both
Number of chromium detected within WHO/NSDWQ limit (MCL)	32	7	39
Percentage of chromium detected within WHO/NSDWQ limit (MCL)	64%	14%	78%
Number of chromium detected above WHO/NSDWQ limit (MCL)	11	—	11
Percentage of chromium detected above WHO/NSDWQ limit (MCL)	22%	—	22%
Minimum concentration detected (mg/L)	<0.001	—	<0.001
Maximum concentration detected (mg/L)	0.215	—	0.215
WHO/NSDWQ MCL (mg/L)	0.05	0.05	0.05
Mean	0.03	0.03	0.03

Table 4.

Level of chromium concentration in groundwater samples.

Parameters	Borehole water	Well water	Both
Number of lead detected within WHO/NSDWQ limit (MCL)	6	—	—
Percentage of lead detected within WHO/NSDWQ limit (MCL)	12%	—	12%
Number of lead detected above WHO/NSDWQ limit (MCL)	37	7	44
Percentage of lead detected above WHO/NSDWQ limit (MCL)	74%	14%	88%
Minimum concentration detected (mg/L)	<0.01	0.13	0.01
Maximum concentration detected (mg/L)	3.26	3.12	3.26
WHO/NSDWQ MCL (mg/L)	0.01	0.01	0.01
Mean	0.51	0.51	0.51

Table 5.

Level of lead concentration in groundwater samples.

Figure 1.

Levels of concentrations of heavy metals (Pb, Cd, Cr, and As) in groundwater sample.

Cadmium comes from two different sources: byproducts of the zinc refining process and naturally occurring ores in rocks and soils [28]. By coming into contact with soil that had been contaminated by discharges from the mining, paint, electroplating, petrochemical, plastics, and fertilizer sectors, groundwater became contaminated with cadmium by leaching [29]. Epidemiological research has shown that chronic exposure to Cd may cause kidney damage, lung cancer, high blood pressure, and bone abnormalities (osteoporosis and osteomalacia) [13, 30]. This is true even though the Cd levels in more than half of the sampled groundwater sources were below the permitted limit (0.003 mg/L) established by the WHO and NSDWQ. Chromium is a naturally occurring element found in volcanic emissions, rocks, soil, plants, and animals. The main types are trivalent (chromium 3) and hexavalent (chromium 6) and can be found in drinking water. The main causes of Cr presence in the groundwater samples could have been natural deposit erosion and coating removal from water pipelines [13, 30]. Despite the fact that Cr concentrations were below the 0.05 mg/L WHO and NSDWQ acceptable range, the health effects of excessive chromium exposure include hepatic and renal impairment while chromate dust is carcinogenic [31, 32].

Due to its deadly and lethal character even at extremely low concentrations, lead is the most significant heavy metal [33]. It can accumulate in body tissue, putting people’s health in peril. The samples examined at various locations contained lead concentrations ranging from 0.01 to 3.26 mg/L, respectively. The majority of the samples revealed lead contents over the 0.01 mg/L permissible level established by the WHO and NSDWQ. The Environmental Protection Agency’s (EPA) permitted threshold is 0 mg/L due to its toxicity. (1) The nearby paint industry’s discharge of lead-rich waste effluents that were deposited in the soil and later made their way into underground water via leaching and (2) the dissolution of industrial heavy plant aerosols and dusts into the soil by heavy rain may be the causes of the high lead concentrations found in some of the sampled groundwater [30, 34]. Hypertension, disturbance of vitamin D and calcium metabolism, impairment of fetal and young children’s brain development, harm to human tissues and organs, and many other difficulties can arise from excessive lead levels in water [13, 30, 35]. Arsenic is present in sulphide complexes such as realgar (As₂S₂), orpiment (As₂S₃), and iron pyrites, to name a few [36]. It is acknowledged as a poison and human carcinogen. Arsenic is included as the most important contaminant at superfund sites on the ATSDR/Environmental Protection Agency (EPA) priority list [37]. Arsenate (+5) predominates when it is hydrated, though arsenite (+3) predominates when anaerobic conditions are present. Although the concentration in groundwater can be significantly greater, its usual concentration in natural streams is less than 1–2 mg/L [13]. Despite the fact that all of the groundwater samples were within the WHO and NSDWQ permissible limits for arsenic concentrations, there is still a chance that arsenic will bioaccumulate in biological systems. The World Health Organization [38] states that melanosis, an abnormal black-brown skin pigmentation, and keratosis, a hardening of the palms and soles, are the first noticeable effects of exposure to low levels of arsenic in drinking water. Keratosis can thicken further (hyperkeratosis), which can lead to skin cancer.

3.3 Socio-demographic characteristics of respondents

The mean age of respondents were 33.7 ± 3.4 years with majority falling within the age group of 30–39 years. Nearly a third-quarter 295(73.8%) of the respondents was males and majority 299(74.8%) has secondary school education. The predominant ethnic group was Yoruba 335(83.8%). Majority 285(71.2%) of the respondents had stay in their present residence for 4 years and above as depicted in Table 6. The high proportion of youth in the survey is suggestive of the demographic distribution of a typical urban settlement in sub-Saharan Africa which serve as a commercial and employment hub for young people. Also the high percentage of Yoruba ethnic group is anticipated since the study was conducted in the southwestern part of Nigeria. These findings are in consonance with the reports of previous authors [6, 39]. The demographic of the survey communities’ also revealed high proportion of semi-literate and artisans/traders. This highlights the poor socio-economic status of residents in the selected communities [39].

Variables	Frequency	Percentage
Age group (year)
10–19	0	0.00
20–29	48	12.0
30–39	186	46.5
40–49	123	30.8
≥50	43	10.7
Total	400	100.00
Gender
Male	295	73.8
Female	105	26.2
Total	400	100.0
Level of education
None	14	3.5
Primary	58	14.5
Secondary	299	74.8
Tertiary	29	7.2
Total	400	100.0
Types of occupation
Civil servant	81	20.2
Artisan	125	31.2
Farming	7	1.8
Others (trader/house wife)	187	46.8
Total	400	100.0
Ethnicity
Yoruba	335	83.8
Igbo	44	11.0
Hausa	21	5.2
Total	400	100.0
Position of respondents in the household
Landlord	168	42.0
Landlady	84	21.0
Tenant	148	37.0
Total	Total	100.0
Duration of living in present residence (in years)
2–3	115	28.8
4–5	128	32.0
6–7	102	25.5
8–9	39	9.7
≥10	16	4.0
Total	400	100.0

Table 6.

Socio-demographic characteristics of respondents.

Mean age of respondents = 33.7 ± 3.4 years.

3.4 Information on water supply

Table 7 presents the information on water supply of the respondents. Majority 357(89.2%) of the respondents reported borehole has the source of water supply in their household. More than a third-quarter 316(79.0%) of the respondents drinks water from groundwater supply while the remaining 84(21.0%) drinks sachet water. Two hundred and fifty eight (81.7%) of the respondents reported that they do not treat their groundwater before drinking while the remaining reported using the following form of treatments: sedimentation; 29(9.2%), boiling; 14(4.4%), coagulation; 7(2.2%), and chlorination; 8(2.5%). The reasons stated by some 258(81.7%) of the respondents for not treating the groundwater before drinking include: groundwater is less harmful; 141(54.7%), no prior knowledge about the treatment; 29(11.2%), it is time wastage; 42(16.3%), drinking it raw from childhood without any negative consequences; 46(17.8%).

Variables	Frequency	Percentage
Source of water supply in household
Borehole	357	89.2
Hand-dug well	43	10.8
Total	400	100.0
Do you drink water from groundwater source?
Yes	316	79.0
No	84	21.0
Total	100	100.0
Source of drinking water
Sachet	84	21.0
Borehole	306	76.5
Hand-dug well	10	2.5
Total	400	100.0
When was your groundwater source dug?
2–3	56	14.0
4–5	106	26.5
6–7	23	5.7
8–9	16	4.0
≥10	8	2.0
No idea	191	47.8
Total	400.0	100.0
Estimated depth of groundwater source
70–89	56	14.0
90–109	58	14.5
110–129	39	9.8
130–149	0	0.0
≥150	14	3.5
No idea	233	58.2
Total	400	100.0
Treatment technique employed by household to make groundwater source safe
No treatment technique	258	81.7
Sedimentation	29	9.2
Boiling	14	4.4
Coagulation	7	2.2
Chlorination	8	2.5
Total	316	100.0
If yes to treatment technique, how often?
Once in a while	9	15.5
Once in 3 month	10	17.2
Once in a year	12	20.7
I cannot say	27	46.6
Total	58	100.0
If no treatment technique, state reasons
Borehole/well water is less harm.	141	54.7
No prior knowledge about it.	29	11.2
Time wastage.	42	16.3
I have been drinking it from childhood and it has no inimical effect on me.	46	17.8
Total	258	100

Table 7.

Water supply information.

Groundwater contributes to both the piped and non-piped domestic water supplies that are found in towns and cities throughout sub-Saharan Africa [40, 41]. Individual choices for household water supply are influenced by issues with accessibility, affordability, dependability, or convenience [42]. The Sustainable Development Goal, objective 6.1, takes availability, accessibility, and safety into consideration. In this study, majority of the households depend on groundwater source for their domestic water supply. The relative closeness of the water supply to the home, which can be acquired at relatively low recurrent cost and, in some circumstances, with cheap upfront inputs, is one of the benefits of self-supply using groundwater sources [42, 43]. Such a supply is available to many houses and can enable a relatively quick response to increasing needs where hydrogeology is advantageous and drillers can provide their services. Aquifers of groundwater, in general, offer long-term storage and can serve as a buffer during dry spells [44, 45, 46]. Furthermore, the majority of homes do not treat their water in any way before using it for drinking. They may have been content with the water’s apparent clarity since they lacked awareness about the toxicity of heavy metals and other toxins found in groundwater. This supported the findings of Abolanle-Azeez et al. [47], who claimed that most households in a small group of Ogun State communities did not treat their water.

3.5 Knowledge of heavy metals contamination among respondents

From Table 8, barely more than one-fifth, 108(27.0%) of the respondents have erudition that groundwater source can be contaminated by heavy metals pollution. Some of the health problems reported by respondents to be caused by drinking water contaminated with heavy metals include: mouth odor; 15(3.8%), poisoning; 79(19.7%), and malaria; 63(15.7%). Respondents believed that arsenic contamination in drinking water can cause the following: typhoid; 106(26.6%), stomach ulcer; 7(1.7%), and dermal problem; 7(1.7%). The respondents reported the following as the health problems associated with cadmium exposure in drinking water: typhoid; 77(19.2%), and kidney problem; 14(3.5%), while chromium exposure in drinking water is believed to cause typhoid; 78(19.5%), liver problem; 8(2.0%); and malaria; 21(5.3%). Ninety-one (22.7%) and 14 (3.5%) of the respondents reported that lead exposure in drinking water can cause typhoid and malaria, respectively. The respondents associated the following to chronic exposure to heavy metals contaminations in drinking water: typhoid; 121(30.2%), cancer; 67(16.8%), and frequent watery stooling; 77(19.2%). From Figure 2, 368(92.0%) of the respondents had poor knowledge of the consequences of heavy metals contamination, 24(6.0%) had fair knowledge while 8(2.0%) had good knowledge.

Variables	Frequency	Percentage
Do you know groundwater source may be contaminated by heavy metals?
Yes	108	27.0
No	160	40.0
Do not know	132	33.0
Total	400	100.0
Drinking water contaminated with heavy metals may cause any of these?
Mouth odor	15	3.8
Poisoning	79	19.7
Malaria	63	15.7
I do not know	243	60.8
Total	400	100.0
Arsenic exposure in drinking water can cause the following?
Stomach ulcer	7	1.7
Typhoid	106	26.6
Dermal problem	7	1.7
I do not know	280	70.0
Total	400	100.0
Cadmium exposure in drinking water can cause the following?
Typhoid	77	19.2
Kidney problem	14	3.5
I do not know	309	77.3
Total	400	100.0
Chromium exposure in drinking water can cause the following?
Typhoid	78	19.5
Liver problem	8	2.0
Malaria	21	5.3
I do not know	293	73.2
Total	400	100.0
Lead exposure in drinking water can cause the following?
Typhoid	91	22.7
Malaria	14	3.5
I do not know	295	73.8
Total	400	100.0
Chronic exposure to heavy metals in drinking water may cause any of these?
Typhoid	121	30.2
Cancer	67	16.8
Frequent watery stooling	77	19.2
I do not know	135	33.8
Total	400	100.0

Table 8.

Knowledge of respondents on heavy metals contamination.

Figure 2.

Respondents knowledge level.

To launch educational programs and public health initiatives, it is crucial to evaluate people’s knowledge of the health issues connected with heavy metal pollution [48]. The majority of people living in the study communities are generally ignorant of the hazardous properties of heavy metals and how they affect human health. Low levels of literacy, the makeup of the communities, and a lack of exposure to information/educational programs on heavy metal toxicity may all contribute to the respondents’ lack of understanding, as seen in this study. The negative health effects of heavy metal poisoning of groundwater are also largely ignored by respondents. This is consistent with the findings of a report from Cui and Forssberg [49] that the majorities of people from low socioeconomic backgrounds are not fully aware of or appropriately informed about the effects of heavy metal poisoning in groundwater.

3.6 Information on respondents’ health status

The following ailments were experienced by the respondents in the last 6 months: frequent watery stool; 31(7.8%), difficulty in breathing; 14(3.5%), and skin infection; 10(2.5%). The respondents reported the following occurrences in their household in the last 1 year: still birth; 10(2.5%), stunted growth in child; 8(2.0%), and death due to cancer; 2(0.5%) in Table 9. According to the study’s findings, a sizable percentage of respondents from the different chosen wards in Sagamu LGA, Ogun State, Nigeria, stated that they had no health issues in the previous 6 months. However, few people reported having frequent intestinal problems and having watery stools, which are signs of diarrhea, typhoid fever, and other gastrointestinal-related illnesses. A negligible percentage of respondents also mentioned having children with cancer, stillbirths, and stunted growth in their households. This can be a result of heavy metal pollution from industrial effluent contaminating the groundwater. This claim is supported by the reports of numerous authors from various states in Nigeria who detailed the detrimental effects of heavy metals in drinking water from groundwater sources on human health. These reports were made by Jatau et al. [50] in Kaduna South Industrial Area; Yaya and Ahmed [51] in the Federal Capital Territory, Abuja; Nwankwoala et al. [52] in the Bayelsa town of Yenegoa; Mile et al. [53] in Makurdi and sub-urban; and Ocheri et al. [54].

Variables	Frequency	Percentage
Which of these ailments have you experienced in the last semester?
Frequent watery stooling	31	7.8
Difficulty in breathing	14	3.5
Skin infection	10	2.5
None	345	86.2
Total	400	100.0
Have you experienced still births in your household in the last 1 year?
Still birth	10	2.5
None	390	97.5
Total	400	100.0
Did any child in your household showed signs of stunted growth in the last 1 year?
Yes	8	2.0
No	392	98.0
Total	400	100.0
Witnessed any death due to cancer in your household in the last 1 year?
Yes	2	0.5
No	398	99.5
Total	400	100.0

Table 9.

Information on respondents health status.

4. Implications of findings and recommendations

The findings of this study have several implications for public health in terms of prevention of heavy metals contamination of groundwater by industrial activities, safeguarding the health and prolonging the lives of the local residents. Consequential to this, is the pivotal role of health promotion and education, as it aims to improve and modify people’s knowledge, attitudes, and practices in order to help them achieve the highest level of salubrity through effective factual information transmission. Findings from this study has shown that there is heavy metals contamination of groundwater source in the selected communities above the permissible limits as recommended by WHO and NSDWQ, and there is reported health consequences among the populaces due to this contamination. Based on these findings, the following recommendations are suggested:

1. All industries effluents and wastewater should be properly treated to removed heavy metals and other contaminants before discharging into the environment,

2. There is need for widespread campaign and awareness program to inform the local residents on the dangers and toxicities associated with consumption of heavy metals contaminated groundwater,

3. Governments should provide facilities that would be used to treat groundwater for local consumption,

4. There is also need to educate agriculturalists and farmers on the appropriate use of pesticides and fertilizers on farmland to prevent leaching of wastewater to groundwater. Additionally, there is need for farmlands to be site away from industrial regions and areas disposed to pollution,

5. Finally, there is an urgent need for the Federal Government of Nigeria through the Ministry of water resources to embark on periodic and consistent monitoring of the underground aquifers nationwide.

5. Conclusion

This chapter present specific details regarding the condition of groundwater’s quality located in communities within the industrial hub of Shagamu, Ogun State, in southwestern Nigeria with the health implications on the local residents. Since the water in the communities’ hand-dug wells and boreholes has a mean pH value that is somewhat acidic, it is an appropriate medium for the breakdown of heavy metals. Additionally, heavy metals were found in the analyzed groundwater, which may be related to the soil’s ability to absorb hazardous waste and untreated effluents from nearby industrial activity into subterranean aquifers. Furthermore, the levels of Pb, Cd, and Cr were higher than the permitted limits set by the WHO and NSDWQ, indicating that the people may be at risk for harmful effects from heavy metals. This proposition is further accentuated by some of the health problems such as diarrhea, stunted growth, still birth and cancer reported by the respondents. Nevertheless, the community residents in the study areas have poor knowledge on heavy metal toxicity and their inimical effects on human health.

Acknowledgments

The contribution and technical assistance of Mr. Femi Oyediran, Managing Director, Environmental Laboratories Limited and Mr. Toyin Bawala during the data collection phase and the laboratory examination of the samples are greatly valued.

Conflict of interest

The authors declare no conflict of interest.

Author contributions

Conceptualization, O.T.O., and A.B.T.; Methodology, O.T.O., and A.B.T.; Validation, O.T.O.; Resources, A.B.T.; Investigation, O.T.O., and A.B.T.; Data Curation, A.B.T.; Data Analysis, O.T.O., A.B.T., and S.A.A.A.; Writing—Original Draft Preparation, A.B.T., S.A.A.A. and S.A.M.A.; Writing—Review and Editing, O.T.O., S.A.A.A., S.A.M.A., and S.A.E.D.; All authors read and approved the final version of the book chapter.

A. Appendices

A.1. Appendix I

S_N	Location	Street	Easting	North	Watertype	Lead	Lead_Conc	Cadmium	Cadmium_Co	Arsenic	Arsenic_Co	Chromium	Chromium_C
1	Eweruku	Eweruku	558,397	745,782	Well	0.13	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
2	Eweruku	Ita Sanni	558,240	745,635	B/H	0.10	POS	0.01	POS	0.0033	NEG	<0.001	NEG
3	Kamalo	Kamalo	558,167	745,519	Well	0.14	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
4	Kamalo	Ewu-Jagun	558,116	745,471	B/H	0.23	POS	0.11	POS	0.0010	NEG	0.036	NEG
5	Kamalo	Ewu-Jagun	558,012	745,605	B/H	0.19	POS	0.04	POS	<0.0001	NEG	0.025	NEG
6	Kamalo	Jagun	557,817	745,533	B/H	0.01	NEG	0.25	POS	0.0037	NEG	0.134	POS
7	Ogijo	Monakare	558,310	744,020	B/H	0.19	POS	0.11	POS	0.0013	NEG	<0.001	NEG
8	Ogijo	Monakare	558,385	743,977	B/H	0.23	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
9	Ogijo	Jacob Clo	558,393	743,774	B/H	0.25	POS	0.01	POS	<0.0001	NEG	<0.001	NEG
10	Ogijo	Jacob Clo	558,425	743,629	Well	0.19	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
11	Ogijo	Opo-Noah	558,514	743,845	B/H	0.16	POS	0.10	POS	0.0019	NEG	0.011	NEG
12	Ogijo	Manakare	558,432	743,960	B/H	0.24	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
13	Ogijo	Ita Yakub	558,139	743,838	B/H	0.31	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
14	Ogijo	Ita Yakub	558,082	743,689	B/H	0.52	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
15	Ogijo	Ifesowapo	557,767	743,225	B/H	0.28	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
16	Ogijo	Ifesowapo	558,088	743,291	B/H	0.52	POS	<0.01	NEG	<0.001	NEG	<0.001	NEG
17	Ogijo	Ifesowapo	557,933	743,225	B/H	<0.01	NEG	0.15	POS	<0.0001	NEG	0.021	NEG
18	Ogijo	Africa Re	557,641	743,013	B/H	0.61	POS	0.32	POS	0.0025	NEG	0.042	NEG
19	Ogijo	Spring Gl	557,585	743,008	B/H	0.65	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
20	Ogijo	Seidu Str	557,337	743,095	B/H	0.30	POS	0.18	POS	0.0037	NEG	0.028	NEG
21	Ogijo	Albarika	557,267	742,684	B/H	<0.01	NEG	<0.01	NEG	<0.0001	NEG	<0.001	NEG
22	Ogijo	Pz Estate	557,388	742,620	B/H	<0.01	NEG	<0.01	NEG	<0.0001	NEG	<0.001	NEG
23	Ogijo	Jumarty P	557,398	742,581	B/H	0.16	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
24	Ogijo	Sah Boliz	557,322	742,646	B/H	0.02	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
25	Ogijo	Goodness	557,163	742,701	B/H	0.40	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
26	Likosi	Likosi Op	559,787	747,741	B/H	0.8900	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
27	Likosi	Likosi Op	559,787	747,749	B/H	0.5700	POS	0.0500	POS	0.0051	NEG	0.0310	NEG
28	Likosi	NNPC Depo	559,994	747,695	B/H	0.7500	POS	0.0800	POS	0.0012	NEG	0.0770	POS
29	Sabo2 Ce	Met	567,667	753,352	B/H	1.0400	POS	0.0700	POS	0.0016	NEG	0.0130	NEG
30	Sabo2 Ce	Basid San	567,759	753,456	B/H	1.0300	POS	<0.01	NEG	0.0014	NEG	0.011	NEG
31	Sabo 2 Ce	Beside Ha	568,101	753,645	Well	1.0500	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
32	Sabo 2 Ce	Oposite L	568,024	753,678	Well	2.2000	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
33	Sabo 2 Ce	Inside La	568,513	753,800	B/H	0.7700	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
34	Sabo 2 Ce	Shagamu I	568,618	753,787	B/H	3.2600	POS	<0.01	NEG	0.0089	NEG	<0.001	NEG
35	Sabo 2	Remo Divi	569,583	754,457	294 B/H	0.0300	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
36	Sabo 2	Bureau of	569,462	754,478	295B/H	<0.01	NEG	<0.01	NEG	<0.0001	NEG	<0.001	NEG
37	Sabo 2	Orirentem	569,826	754,641	B/H	<0.01	NEG	0.0300	POS	<0.0001	NEG	0.0110	NEG
38	Kara Sabo	Oak Heigh	569,859	754,650	B/H	0.16	POS	0.15	POS	0.0070	NEG	0.062	POS
39	Sabo 1 Ka	249 Akari	569,887	754,687	B/H	0.2100	POS	0.3600	POS	0.0001	NEG	0.1470	POS
40	Sabo 1 Ka	Vkay Hote	569,949	754,699	Well	0.2900	POS	0.12	POS	<0.0001	NEG	0.1030	POS
41	Sabo 1 Ka	Amen Hosp	569,989	754,756	Well	0.0700	POS	0.2700	POS	0.0021	NEG	0.0720	POS
42	Sabo 1 Ka	Kara	570,079	754,818	B/H	0.1700	POS	0.2000	POS	0.0032	NEG	0.0350	NEG
43	Sabo 1 Ka	5 Musubau	570,133	754,708	Well	0.3500	POS	0.4300	POS	0.0041	NEG	0.1390	POS
44	Sabo 1 Ka	10 Musuba	570,164	754,673	29 Well	0.9700	POS	0.1600	POS	0.0017	NEG	0.0530	POS
45	Sabo 1 Ka	Orepitan	570,063	754,625	301 Well	0.53	POS	0.26	POS	0.0011	NEG	0.124	POS
46	Sabo 1 Ka	Kara	570,148	754,921	302 B/H	1.1200	POS	0.1200	POS	<0.0001	NEG	0.0910	POS
47	Sabo 1 Ka	5 Kolawol	570,138	755,066	303 B/H	1.5500	POS	0.22	POS	0.0013	NEG	0.215	POS
48	Sabo 1 Ka	10 Kolawo	570,052	755,066	304 Well	3.12	POS	<0.01	NEG	0.0061	NEG	0.029	NEG
49	Sabo 1 Ka	243 Akari	570,236	754,900	305 Well	0.29	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG
50	Sabo 1 Ka	237Akarig	570,276	754,953	Well	0.18	POS	<0.01	NEG	<0.0001	NEG	<0.001	NEG

A.2. Appendix II: Results of pH, conductivities, temperature and TDS

S/N	Water type	pH	Conductivity (μ^2/cm)	TDS (mg/L)	Temp. (°C)
001	Well	4.5	0090	0040	27.7
002	B/H	5.5	0030	0010	30.5
003	Well	4.1	0060	0020	30.4
004	B/H	4.5	0030	0010	31.4
005	B/H	5.0	0040	0010	29.0
006	B/H	4.7	0090	0030	29.3
007	B/H	4.4	0030	0010	28.4
008	B/H	4.5	0020	NIL	29.4
009	B/H	4.5	0030	0010	28.7
010	Well	4.5	0020	NIL	31.0
011	B/H	4.4	0020	NIL	30.8
012	B/H	4.2	0020	NIL	31.6
013	B/H	4.0	0020	NIL	28.2
014	B/H	4.6	0020	NIL	28.5
015	B/H	4.4	0020	NIL	29.3
016	B/H	4.5	0030	0010	34.5
017	B/H	4.3	0020	NIL	30.7
018	B/H	4.0	0020	NIL	32.0
019	B/H	4.1	0020	NIL	31.1
020	B/H	5.1	0030	0010	32.2
021	B/H	4.4	0030	0010	28.5
022	B/H	4.7	0010	NIL	31.8
023	B/H	4.1	0010	NIL	30.5
024	B/H	3.8	0020	NIL	30.5
025	B/H	4.8	0030	0010	28.9
026	B/H	4.8	0030	0010	27.1
027	B/H	6.0	0440	0210	30.0
028	B/H	7.0	0520	0250	32.2
029	B/H	7.5	0530	0130	31.0
030	B/H	7.0	0280	0070	31.0
031	B/H	5.7	0160	0050	29.4
032	B/H	5.9	0470	0230	29.2
033	B/H	7.6	0480	0260	31.1
034	B/H	7.9	0050	0200	30.1
035	B/H	7.7	0100	0240	29.2
036	B/H	6.0	0180	0230	28.8
037	B/H	4.9	0240	0020	29.6
038	B/H	4.9	0660	0040	32.8
039	B/H	4.7	0430	0080	29.0
040	Well	5.3	0210	0110	29.8
041	B/H	5.7	0030	0320	32.1
042	B/H	5.8	0040	0210	29.4
043	Well	5.8	0710	0100	30.1
044	Well	5.1	0750	0360	32.7
045	B/H	6.0	0450	0220	29.0
046	B/H	5.6	0360	0170	32.1
047	B/H	4.3	0290	0140	31.2
048	Well	5.0	0620	0300	31.9
049	Well	4.2	0400	0190	32.9
050	Well	4.0	0420	0200	32.1

A.3. Appendix III: GIS map of Ogijo/Likosi and Sabo 1 and 2

Figure A1.

Map showing sample locations in Ogijo/Likosi ward 10.

Figure A2.

Map showing sample locations in Sabo ward 4 and 5.

Figure A3.

Map showing lead concentration distribution in Ogijo/Likosi ward 10.

Figure A4.

Map showing lead concentration distribution in Sabo ward 4 and 5.

Figure A5.

Map showing cadmium concentration distribution in Ogijo/Likosi ward 10.

Figure A6.

Map showing cadmium concentration distribution in Sabo ward 4 and 5.

Figure A7.

Map showing chromium concentration distribution in Ogijo/Likosi ward 10.

Figure A8.

Map showing chromium concentration distribution in Sabo ward 4 and 5.

Figure A9.

Map showing arsenic concentration distribution in Ogijo Likosi ward 10.

Figure A10.

Map showing arsenic concentration distribution in Sabo ward 4 and 5.