International Scholarly Research Notices
Volume 2014 (2014), Article ID 252148, 37 pages
http://dx.doi.org/10.1155/2014/252148

Review Article

A Systematic Review of Heavy Metals of Anthropogenic Origin in Environmental Media and Biota in the Context of Gold Mining in Ghana

Frederick Ato Armah,1,2 Reginald Quansah,³ and Isaac Luginaah⁴

¹Environmental Health and Hazards Laboratory, Department of Geography, Western University, 1151 Richmond Street, ON, Canada N6A 5C2
²Department of Environmental Science, School of Biological Sciences, University of Cape Coast, Cape Coast, Ghana
³Biological, Environmental & Occupational Health Sciences, School of Public Health, University of Ghana, Legon, Accra, Ghana
⁴Department of Geography, Western University, 1151 Richmond Street, ON, Canada N6A 5C2

Received 16 June 2014; Accepted 10 July 2014; Published 9 November 2014

Academic Editor: Constantine Stalikas

Copyright © 2014 Frederick Ato Armah et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Heavy metal accumulation in the food chain is an issue of global concern because it eventually leads to toxic effects on humans through the water we drink, contaminated soils, crops, and animals. Reports of toxicant levels in environmental media (air, water, and soil) and biota in Ghana were sought in SCOPUS, PubMed, MEDLINE, and EMBASE. Of 1004 bibliographic records identified, 54 studies were included in evidence synthesis. A disproportionately large number of papers (about 80%) focused exclusively on environmental media. Papers focusing on biomonitoring and human health were relatively few. Studies reported a high degree of spatial variability for the concentrations of 8 metals in groundwater. Generally, heavy metal concentrations in soil reported by the studies reviewed were higher than metal concentrations in riverine sediments. Urine and hair were the most common biological markers of heavy metal exposure used by the studies reviewed unlike nails, which were sparingly used. By and large, published results on the levels of heavy metals in goldmine and non-mine workers yielded contradictory results. Mostly, concentrations of heavy metals reported by the studies reviewed for nails were higher than for hair. A high degree of variability in the heavy metal concentrations in human subjects in the studies reviewed is likely due to heterogeneity in physiological states, excretion profiles, and body burdens of individuals. These, in turn, may be a product of genetic polymorphisms influencing detoxification efficiency.

1. Introduction

Over the past three decades, the term “heavy metals” has been widely used in the scientific literature on ecotoxicology. It is frequently considered as an assemblage name for metals and semimetals (metalloids) that have been linked with contamination and potential toxicity or ecotoxicity [1]. The term “heavy metals” has, however, been used inconsistently in the scientific literature. This has culminated in considerable misperception of the significance of the term. There is also a propensity to suppose that all the so-called “heavy metals” have highly toxic or ecotoxic properties [1]. According to Duffus [1], the scientifically sound designations of elements generally considered as heavy metals are as follows: As, Cd, Hg, Pb, and Sb (Chalcophile); Fe, Co, Cu, Ni, and Zn (lithophile/chalcophile); and Mn and Cr (lithophile). Despite some recognition that the term “heavy metals” is a misnomer, we resort to its use in this paper for two fundamental reasons. First, although the term “heavy metals” has been queried over many years, for example, by Phipps [2], and by Loon and Duffy [3], efforts to replace it by chemically sound terminology have so far failed. Secondly, all the papers systematically reviewed in this study specifically used the term “heavy metals.”

Heavy metals in water, sediments, air, and other environmental media are of great environmental concern because of their potential long-term effects on human health particularly in developing countries where remedial techniques are nascent [4–8]. The origin of such metals in the natural environment is either geogenic or anthropogenic releases [9, 10]. In general, the anthropogenic releases constitute a constant source of pollution, whereas surface runoff is a seasonal phenomenon which is influenced by climate within the environmental system. The concentrations of heavy metal (loid)s in soils and other environmental media can vary widely, even in uncontaminated environments. Noticeable dissimilarities in the geochemical composition of the rocks which constitute the parent materials of soils and disparities in the strength of soil-forming processes can lead to extensive ranges of total and available concentrations of most elements in soils, even in those unaffected by contamination [4]. Nevertheless, contamination from many sources can often give rise to some very high concentrations of heavy metal (loid)s [4] which can cause toxicity in soil organisms and susceptible plants, but this depends on the factors affecting the bioavailability of the elements [4]. Many investigations have been conducted on anthropogenic contaminants of ecosystems across the globe [11, 12].

In Ghana, which exemplifies a country where extensive research on heavy metals has hitherto been carried out because of its extensive mining industry, one of the main anthropogenic sources of concern is gold mining, both surface and underground. Gold mining is widespread and according to Naylor [13], it contributes about 44% of Ghana’s export earnings. The large-scale extraction of gold occurs predominantly in the Western and Ashanti regions for example, Bibiani and Obuasi, and is accompanied by arsenic, mercury, and sulphur contamination to surface and groundwater bodies, soil and even air pollution causing acid rain and degradation to the surrounding environment and impacts on human health [14, 15]. With the liberalization of the gold mining sector in the mid-1980s, gold mining-dependent livelihoods have soared, employing extraction methods that invariably release mercury into surrounding water sources [5, 16, 17]. In the past, gold mining was restricted to the south; lately however, exploration is increasing in the north, especiallyin the Upper East Region. Iron and manganese have also been found in elevated concentrations in water in Ghana [9]. This has culminated in the closure of hundreds of wells in favour of surface waters likely contaminated with harmful microorganisms [18]. Up till now, mining related studies in Ghana conducted on environmental samples (water, air, soil, sediment, etc.) and biota (fish, urine, blood, nails, etc.) include Hg [19, 20], As [14, 15], Fe and Mn [9, 21], Pb [7, 18], and Cd and Cu [5, 16, 17].

Despite the large body of literature that has been devoted to heavy metal pollution in Ghana, the results are mixed and are disparate making it quite difficult to elicit a coherent account on the scope and levels of heavy metal pollution in the environment and in biota, especially in humans, across Ghana. Consequently, this study aims to cumulate scientific evidence on heavy metal pollution in the environment and in biota in Ghana through synthesis of existing data. This systematic review was conducted for a variety of reasons, but it was not limited to the synthesis of evidence on the magnitude of heavy metal contamination or to supporting evidence-based policy or practice. This review provides useful information for designing future research on heavy metal pollution in Ghana and other jurisdictions. In particular, it will help to place future studies in context by describing what we knew before and what we hoped to learn from any future study on heavy metal pollution in Ghana and in other contexts.

2. Materials and Methods

2.1. Search Strategy and Study Selection

The systematic search and review processes were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement criteria as proposed by Liberati et al. [22]. We searched SCOPUS, PubMed, MEDLINE (http://www.ncbi.nlm.nih.gov/pubmed/), and EMBASE (http://www.embase.com/home) databases using the following search terms: “Ghana” successively combined with “heavy metals,” “pollutant,” “toxic element,” “metalloid,” “arsenic,” “cadmium,” “mercury,” “lead,” “cobalt,” “zinc,” “manganese,” “iron,” “nickel,” and “chromium.” The search was limited to papers published till January 2013 and yielded 1004 bibliographic records. The bibliographic records were complemented with attempts of search for other research by key authors and search of citations and reference lists of key reports and related articles. After importing bibliographic records duplicates were deleted and reports were scrutinized using Zotero 2.03. All studies presenting quantitative data on levels of arsenic, cadmium, lead, mercury, chromium, cobalt, nickel, manganese, iron, tin, and zinc in environmental media (soil, water, sediment, and air) and or biologic specimen (hair, urine, blood, nails, and food) were included, regardless of experimental design, or methods of collection of samples, or chemical analysis.

2.2. Data Extraction

Using a standard, purpose-designed form, we extracted the following data from each paper: (a) study design, date and place, sampling method and size, inclusion and exclusion criteria, and request for informed consent; (b) protocol for collection, storage, processing, and analysis of biologic specimens; and (c) results, including metal levels and related factors.

3. Results

3.1. Description of the Studies

Of 1004 bibliographic records of relevance to the gold mining context in Ghana identified, 594 did not meet inclusion criteria at first screening, 83 full-text articles were sought for full-text screening, and 65 were obtained and screened. Fifty-four studies were included in evidence synthesis. Searching, screening, and study inclusion are summarized in the flow diagram, Figure 1.

Figure 1: Schematic diagram of search strategy.

The main characteristics of each study are described in Tables 3, 4(a)–4(c), and 5(a)–5(e). Whereas older studies (from mid 1970s through early 1990s) on heavy metals in environmental media and biologic specimens in Ghana were mainly undertaken along the Ashanti gold belt in south western Ghana (to a large extent in Obuasi and to some extent in Tarkwa), studies targeting environmental media in the northern parts of Ghana began to be published only in the early 2000s and accounted for an ample fraction (20%) of published works from 2000 and later. Of the reviewed articles, the earliest study on heavy metals in environmental media and biologic specimens in Ghana was undertaken by Simeonov et al. [23]. Thereafter, there was an almost twenty-year lull in research on heavy metals before the work of Amonoo-Neizer and Amekor [14].

3.2. Research Design and Objectives

All the papers reviewed were cross-sectional studies with three distinct types of objective, often combined in the same study, that is, assessment of levels of heavy metals in the media, spatial variability of the metals, and compliance with environmental and regulatory standards. None of the studies monitored heavy metal concentrations in environmental media or biologic specimens across time (longitudinally). Broadly, studies adopted either an environmental monitoring or a bio-monitoring perspective. A disproportionately large number of papers (about 80%) focused exclusively on environmental media. Out of the 54 articles reviewed, twelve papers devoted attention to heavy metals in either cooked (fish) or uncooked food (vegetables, fruits) or other plants (lichens).

Papers focusing on biomonitoring and human health were few and far between. In total, 10 articles focused on heavy metals in humans. As shown in Tables 1(a) and 1(b), six papers analysed heavy metals in human hair. Eight manuscripts measured heavy metals in human urine and only two articles focused on heavy metals in human blood. Also, two measured heavy metals in human nails. Of the studies reporting on human subjects, only one reported on 1 biomarker of exposure (hair), whereas another study reported on three biomarkers (hair, blood, and urine). The rest reported on at most two biomarkers (see Tables 1(a) and 1(b)). Regarding ethical considerations, 6 papers on human subjects specifically mentioned informed consent as a prerequisite for study participation and 2 papers, mostly recent, stated the approval of an ethics committee.

Table 1: Levels of heavy metals in humans.

(a)

Reference (sample type)
Sample type/region/community
As
Hg
Fe
Mn
Cd
Zn
Cr
Cu
Pb

Amasa 1975 [31]
Hair/Ashanti region/Obuasi mine workers (PTP)
336.33 (196–1940) mgkg⁻¹
—
—
—
—
—
—
—
—

Hair/Ashanti region/Obuasi mine workers (shaft)
25.59 (7.7–78.0) mgkg⁻¹
—
—
—
—
—
—
—
—

Hair/Ashanti region/Obuasi non-mine workers
38.7 (8.8–268) mgkg⁻¹
—
—
—
—
—
—
—
—

Adimado and Baah 
2002 [35]
Blood/western region/
—
102 (55.8)
—
—
—
—
—
—
—

Urine/western region/
—
34.2 (36)
—
—
—
—
—
—
—

Hair/western region/
—
1.61 (1.33)
—
—
—
—
—
—
—

Nail/western region/
—
2.65 (2.0)
—
—
—
—
—
—
—

Essumang 2009 [55]
Hair/Western region/
0.0142–0.0515 μgg⁻¹
—
—
—
—
—
—
—
—

Paruchuri et al. 2010 [56]
Urine/Upper East region/
—
17.0 μgL⁻¹
—
—
—
—
—
—
—

Paruchuri et al. 2010 [56]
Hair/Upper East region/
—
1.1 μgg⁻¹
—
—
—
—
—
—
—

Basu et al. 2011 [57]
Urine/Upper East region/
114.52 μgL⁻¹
—
—
2.01 μgL⁻¹
0.45 μgL⁻¹
601.27 μgL⁻¹
26.58 μgL⁻¹
40.85 μgL⁻¹
1.34 μgL⁻¹

Abrefah et al. 2011 [58]
Urine/Western region/
14.75 μgL⁻¹
0.56 μgL⁻¹
—
—
—
—
—
—
—

Asante et al. 2012 [59]
Urine/Greater Accra region/
54.4 (45.6) μgL⁻¹
<0.5 μgL⁻¹
180 (150) μgL⁻¹
4.08 (2.39) μgL⁻¹
0.43 (0.17) μgL⁻¹
752 (520) μgL⁻¹
19 (7) μgL⁻¹
305 (117) μgL⁻¹
0.08 (0.01–0.08) μgL⁻¹

Adimado and Baah  2002 [35]
Blood/Western region/Anwiaso
—
102 (30.2–218) μgL⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Urine/Western region/Anwiaso
—
34.2 (1.0–183) μgL⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Hair/Western region/Anwiaso
—
1.61 (0.15–5.86) μgg⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Nail/Western region/Anwiaso
—
2.65 (0.57–10.0) μgg⁻¹
—
—
—
—
—
—
—

Asante et al. 2007 [15]
Urine (mine workers)/Western region/Tarkwa and its environ
70.6 (8–270) μgL⁻¹
0.35 (0.10–0.61) μgL⁻¹
—
1.56 (1.0–2.4) μgL⁻¹
0.03 (0.03–0.11) μgL⁻¹
1.71 (0.10–0.42) μgL⁻¹
8.15 (2.6–25.1) μgL⁻¹
561.07 (64.1–1230) μgL⁻¹
0.028 (0.01–0.08) μgL⁻¹

Asante et al. 2007 [15]
Urine (non-mine workers)/Western region/Tarkwa and its environ
83.85 (4.7–123) μgL⁻¹
3.84 (0.6–86.0) μgL⁻¹
—
1.98 (0.2–4.1) μgL⁻¹
0.23 (0.01–0.27) μgL⁻¹
0.54 (0.10–5.65) μgL⁻¹
29.78 (3.7–103) μgL⁻¹
792.18 (159–1600) μgL⁻¹
0.034 (0.01–0.26) μgL⁻¹

Asante et al. 2012 [59]
Urine (e-waste recycling workers)/Greater Accra region/Agbogbloshie
0.34 (0.10–0.76) μgL⁻¹
—
13 (5.3–21) μgL⁻¹
5.19 (1.18–10.0) μgL⁻¹
0.07 (<0.01–0.19) μgL⁻¹
94.2 (7.85–711) μgL⁻¹
0.38 (0.04–1.5) μgL⁻¹
20.8 (5.89–52.0) μgL⁻¹
0.40 (0.09–1.23) μgL⁻¹

Adimado and Baah  2002 [35]
Blood/Western region/Tanoso
—
16.5 (2.1–57.2) μgL⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Urine/Western region/Tanoso
—
6.4 (2.0–14.3) μgL⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Hair/Western region/Tanoso
—
4.27 (0.06–28.3) μgg⁻¹
—
—
—
—
—
—
—

Adimado and Baah  2002 [35]
Nail/Western region/Tanoso
—
3.45 (0.13–22.6) μgg⁻¹
—
—
—
—
—
—
—

Kwaansa-Ansah et al. 2010 [60]
Hair (Farmers)/Central region/Dunkwa-On-Offin
—
2.35 (0.63–7.19) μgg⁻¹
—
—
—
—
—
—
—

Urine (Farmers)/Central region/Dunkwa-On-Offin
—
0.69 (0.075–2.31) μgL⁻¹
—
—
—
—
—
—
—

Kwaansa-Ansah et al. 2010 [60]
Hair (miners)/Central region/Dunkwa-On-Offin
—
2.14 (0.57–6.07) μgg⁻¹
—
—
—
—
—
—
—

Urine (miners)/Central region/Dunkwa-On-Offin
—
1.23 (0.32–3.62) μgL⁻¹
—
—
—
—
—
—
—

(b)

Reference (sample type)
Sample type/region/community
Ni
Co
Cr
Se
Sb
Sr
Rb

Basu et al. 2011 [57]
Urine/Upper East region/
6.51 μgL⁻¹
2.32 μgL⁻¹
26.58 μgL⁻¹
39.4 μgL⁻¹
—
—
—

Asante et al. 2012 [59]
Urine/Greater Accra region/
—
—
—
—
1.1 (0.6) μgL⁻¹
142 (108) μgL⁻¹
2090 (1070) μgL⁻¹

Fianko et al. 2007 [61]
Rivers supplying water to Iture Estuary
—
—
—
—
—
—
—

Sorowie
—
—
—
2.1 μgL⁻¹
—
—
—

Kakum
—
—
—
1.9 μgL⁻¹

—
—

Asante et al. 2007 [15]
Urine (mine workers)/Western region/Tarkwa and its environ
—
404.6 (174–676) μgL⁻¹
—
3267.13 (207–8120) μgL⁻¹
4.36 (0.8–8) μgL⁻¹
—
243.89 (21–545) μgL⁻¹

Asante et al. 2007 [15]
Urine (non-mine workers)/Western region/Tarkwa and its environ
—
397.98 (72.7–580) μgL⁻¹
—
4394.12 (210–9660) μgL⁻¹
8.17 (1–22) μgL⁻¹

217.93 (15.6–558) μgL⁻¹

Asante et al. 2012 [59]
Urine (e-waste recycling workers)/Greater Accra region/Agbogbloshie
—
0.09 (0.049–0.22) μgL⁻¹
—
0.1 (<0.1–0.4) μgL⁻¹
<0.1 (<0.1–0.16) μgL⁻¹
124 (56.8–197) μgL⁻¹
3.85 (1.09–6.75) μgL⁻¹

3.3. Analytical Methods: Collection, Processing, and Analysis of Biologic Specimens

Period of collection of environmental samples and biologic specimens, which was not always specified, varied extensively as shown in Table 3. For instance, more than 20% of articles reviewed did not report period of data collection (11 papers). Similarly, pretreatment of environmental samples, which was not always specified, varied widely. In general, the environmental and biologic samples (water, urine, blood, etc.) were frozen and stored before laboratory analyses. A variety of spectrometry was used to determine levels of heavy metals. These include UV-visible spectrophotometry (2 papers), cold vapour atomic absorption spectrophotometry (5 papers), instrumental neutron activation analysis (10 papers), inductively coupled plasma mass spectrometry (ICP-MS) (4 papers), and inductively coupled plasma-optical emission spectroscopy (ICP-OES) (1 paper). Other techniques included flame atomic absorption spectrophotometry (12 papers), high performance liquid chromatography (HPLC) (1 paper), inductively coupled plasma atomic emission spectrometer (ICP-AES) (1 paper), and atomic absorption spectrophotometry (6 papers). Five studies did not report the analytical method used in the determination of heavy metals in environmental media or biologic samples.

Information on laboratory quality controls differed between the earliest and the more recent papers. Before the year 2000, none of the studies specified having internal quality controls or external controls. In contrast, all studies published after 2005 (7 papers) reported the use of standardized quality control procedures that generally comprised evaluation of accuracy and precision by analysis of certified reference material; however, no studies included additional inter-laboratory comparisons. Only about one-third of the studies specified the limit of detection (LOD), merely stating the value or including the procedure used to treat values below it.

3.4. Statistical Analyses and Reporting of Results

Most of the studies (>90%) provided measures of central tendency, that is, arithmetic means, usually accompanied by standard deviations (SDs). Geometric mean was not reported in any of the papers. Other widely used indicators of dispersion and central tendencies were range (more than 40 studies) and median (15 studies). Without exception, authors neither include confidence intervals nor mention the evaluation of outliers or the use of robust measures of central trend. Studies assessing associations with risk factors generally provided either Pearson’s product moment or Spearman’s correlation coefficients drawn from univariate analyses or differences in means derived from stratified analyses; few papers (2 papers) carried out multivariate analyses.

3.5. Levels of Heavy Metals in Underground Water and Water from Boreholes

Studies reported a high degree of spatial variability for the concentrations of 8 metals (As, Hg, Cd, Cr, Pb, Co, Sr, and Mn) in boreholes as shown in Table 2. The lowest concentration of As (<1 μgL⁻¹) was reported by Akabzaa et al. [24] for the Anglogold Ashanti area in Obuasi. The highest concentration of As (12200 μgL⁻¹) was reported by Boadu et al. [25] for the Konongo Old mining shaft. The lowest concentration of Hg (<0.05 μgL⁻¹) was reported by Asante et al. [15] for the Tarkwa gold mining area, whereas the highest Hg concentration of 6251 μgL⁻¹ was reported by Essumang et al. [16] for the Wassa West District. The lowest concentration of Cd (<0.06 μgL⁻¹) was reported by Asante et al. [15] for the Tarkwa gold mining area and the highest Cd concentration of 7.6 μgL⁻¹ was reported by Tay and Momade [26] for the northern part of the Ashanti gold belt. The lowest concentration of Cr (0.03 μgL⁻¹) was reported by Asante et al. [15] for the Tarkwa gold mining area, whereas the highest Cr concentration of 45 μgL⁻¹ was reported by Essumang et al. [16] for the Dumasi community in the Wassa West District. Three studies [15, 24, 27], severally reported the lowest Pb concentration of 0.01 μgL⁻¹. However, Akabzaa et al. [24] reported the highest Pb concentration (96 μgL⁻¹) within the vicinity of the Obuasi goldmine. The lowest concentration of Co (0.02 μgL⁻¹) was reported by Asante et al. [15] for the Tarkwa gold mining area, whereas the highest Co concentration of 50 μgL⁻¹ was reported by Essumang et al. [16] for the Dumasi community in the Wassa West District.

Table 2: Levels of metals in water from boreholes by region in Ghana.

Reference
Numbers of boreholes/community
As
Hg
Fe
Mn
Cd
Zn
Cr
Cu
Pb

Ashanti region

Amasa 1975 [31]
Boreholes in selected communities in Obuasi area
2250 μgL⁻¹
—
—
—
—
—
—
—
—

Smedley 1996 [62]
4 boreholes in selected communities in Obuasi area
53.75 (14–64) μgL⁻¹
—
2046.3 (980–4447) μgL⁻¹
220 (79–313) μgL⁻¹
—
126.5 (3–226) μgL⁻¹
<0.3 μgL⁻¹
1.45 (0.7–2.4) μgL⁻¹
<0.06 μgL⁻¹

Boadu et al. 2000 [25]
Underground water at Konongo old mining shaft
11,950 (11,700–12,200) μgL⁻¹
—
—
—
—
—
—
—
—

—
—
—
—
—
—
—
—

Akabzaa et al.
2007 [24]
Obuasi and its environ

—
—
—
—
—
—
—
—

8 boreholes in communities within the operating area of AGC
282.7 (15–801) μgL⁻¹
2.5 μgL⁻¹
2570.7 (21–5342) μgL⁻¹
106.14 (43–248) μgL⁻¹
<2.0 μgL⁻¹
43 (14–117) μgL⁻¹
—
46.4 (1–94) μgL⁻¹
36.3 (1–96) μgL⁻¹

5 boreholes in communities immediately downstream
<1 μgL⁻¹
2.5 μgL⁻¹
517.5 (40–1811) μgL⁻¹
124.5 (1–329) μgL⁻¹
<2.0 μgL⁻¹
40.9 (12–127) μgL⁻¹
—
19.25 (3–44) μgL⁻¹
24 (5–48) μgL⁻¹

Akabzaa et al.
2007 [24]
15 bores in the vicinity of Obuasi mine
82 (9–801) μgL⁻¹
4 (1–9) μgL⁻¹
1343 (19–15340) μgL⁻¹
120 (1–329) μgL⁻¹
2 (2–9) μgL⁻¹
42 (4–127) μgL⁻¹
—
25 (1–94) μgL⁻¹
16 (<0.01–96) μgL⁻¹

Tay and Momade 2006 [26]
67 boreholes, 24 wells in the northern part of the Ashanti Gold belt
—
—
—
—
—
—
—
—
—

—
205 μgL⁻¹
775 μgL⁻¹
525 μgL⁻¹
10 μgL⁻¹
—
—
—
—

September (light rains)
—
190 (<1.0–520) μgL⁻¹
990 (10–2120) μgL−1
620 (10–1090) μgL⁻¹
10 (1–24) μgL⁻¹
—
—
—
—

June (heavy rains)
—
220 (100–700) μgL⁻¹
560 (200–2360) μgL⁻¹
430 (10–30) μgL⁻¹
10 (<1–76) μgL⁻¹
—
—
—
—

Amedjoe et al. 2012 [63]
22 boreholes and hand dug wells in the Obuasi area (wet-June + dry-Feb seasons)
570 (240–1320) μgL⁻¹
—
170 (30–480) μgL⁻¹
—
—
50 (30–480) μgL⁻¹
—
—
—

Western region

—
—
—
—
—
—
—
—

Asante et al. 2007 [15]
March (Light rains)
12 boreholes in selected communities in Tarkwa area
1.3 (0.5–1.0) μgL⁻¹
<0.5 (<0.5–2.3) μgL⁻¹
—
797 (2.24–4970) μgL⁻¹
0.06 (0.01–0.16) μgL⁻¹
10.3 (1.82–24.5) μgL⁻¹
0.78 (0.03–2.1) μgL⁻¹
4.29 (0.93–11.1) μgL⁻¹
0.16 (0.01–0.32) μgL⁻¹

Obiri 2007 [64] (August 2004 to June 2005)
4 boreholes in Dumasi in Wassa West District
5142 (4987–6521) μgL⁻¹
—
7855 (7520–8515) μgL⁻¹
374 (111–586) μgL⁻¹
3.35 (2–5) μgL⁻¹
6.68 (6-7) μgL⁻¹
42 (26–45) μgL⁻¹
—
6.56 (5–8) μgL⁻¹

Asante et al. 2007 [15] (March 2004)
12 boreholes in selected communities in Tarkwa area
1.3 (0.5–4.0) μgL⁻¹
<0.05–2.30 μgL⁻¹
—
797 (2.2–4970) μgL⁻¹
0.06 (0.01–0.16) μgL⁻¹
10.3 (1.82–24.5) μgL⁻¹
0.78 (0.46–1.8) μgL⁻¹
4.29 (0.93–11.1) μgL⁻¹
0.16 (0.01–0.32) μgL⁻¹

Armah et al. 2011 [65]
Tarkwa mining area
4 (<0.1–22.0) μgL⁻¹
—
144 (<0.1–1499) μgL⁻¹
100 (<0.1–1500) μgL⁻¹
2 (<0.1–28) μgL⁻¹
0.5 (0.4–3.6) μgL⁻¹
0.2 (<0.1–1.0) μgL⁻¹
0.2 (0.4–717) μgL⁻¹
3.7 (0.4–34.1) μgL⁻¹

Eastern Region

Kortatsi et al. 2008 [66]
45 boreholes in selected communities in the Eastern region
5.5 (<2–9) μgL⁻¹
—
—
—
—
—
—
—
—

Tay and Kortatsi
2008 [47]
Boreholes from 68 communities in the Eastern region

—
—
—
—
—
—
—
—

22 communities in the Suhum districts

10 (10–400) μgL⁻¹
100 (10–500) μgL⁻¹

—
—
—
—

15 communities in the Akim districts

88.6 (10–500) μgL⁻¹
135.4 (10–500) μgL⁻¹

—
—
—
—

7 communities in the Akwapim district

40 μgL⁻¹
20 μgL⁻¹

Greater Accra Region

Kortatsi et al. 2008 [66]
21 boreholes in selected communities in the Greater Accra region
3.5 (<2–5) μgL⁻¹
—
—
—

—
—
—
—

Tay and Kortatsi   
2008 [47]
Boreholes in 24 communities in the Ga districts

40 (10–1010) μgL⁻¹
40 μgL⁻¹

—
—
—
—

Volta Region

—
—
—
—

Tay 2007 [67]
34 boreholes at Akatsi area

270 (10–3120) μgL⁻¹
330 (10–1450) μgL⁻¹

—
—
—
—

27 boreholes at Ketu area

350 (<1–1510) μgL⁻¹
2350 (10–1450) μgL⁻¹

—
—
—
—

Kortatsi et al. 2008 [66]
44 boreholes in selected communities in the Volta region
15 (<2.0–28) μgL⁻¹

Reference
Number of boreholes/community
Ni
Co
Cr
Cd
Se
Th
Sb
Sr
Mn

Ashanti region

Smedley 1996 [62]
4 boreholes in selected communities in Obuasi area
1.54 (1–2.4) μgL⁻¹
2.36 (0.73–5.57) μgL⁻¹
<0.3 μgL⁻¹
—
—
—
<0.04 μgL⁻¹
277.75 (125–380) μgL⁻¹
—

Akabzaa et al.
2007 [24]
15 bores in the Vicinity of Obuasi mine
13 (2–46) μgL⁻¹

2 (2–9) μgL⁻¹

Tay and  Momade 2006 [26]
67 boreholes, 24 wells in the northern part of the Ashanti Gold belt

45 μgL⁻¹

September (light rains)
<10 μgL⁻¹

June (heavy rains)
45 (10–80) μgL⁻¹

Western region

Asante et al. 2007 [15]
March (Light rains)
12 boreholes in selected communities in Tarkwa area

2.5 (0.02–8.9) μgL⁻¹
0.78 (0.03–2.1) μgL⁻¹

291 (19–1320) μgL⁻¹

Obiri 2007 [64] (August 2004 to June 2005)
4 boreholes in Dumasi in Wassa West District

33.25 (10–50) μgL⁻¹

3.5 (2–5) μgL⁻¹

Asante et al. 2007 [15] (March 2004)
12 boreholes in selected communities in Tarkwa area

2.5 (0.07–8.9) μgL⁻¹
0.78 (0.03–2.1) μgL⁻¹

291.04 (19–1320) μgL⁻¹

Armah et al. 2011 [65]

4 (3) μgL⁻¹
—
0.2 (<0.1–1.0) μgL⁻¹
2 (<0.1–28) μgL−1
—
—
—
—
100 (<0.1–1500) μgL−1

Tay 2007 [67]
34 boreholes at Akatsi area

40.79 (1.2–111.7) μgL⁻¹

27 boreholes at Ketu area

47.39 (4.3–183) μgL⁻¹

Tay and Kortatsi
2008 [47]
Boreholes in 24 communities in the Ga districts

37400 (7700–306000) μgL⁻¹

Tay and Kortatsi
2008 [47]
22 communities in the Suhum districts

11900 (1400–132900) μgL⁻¹

Tay and Kortatsi
2008 [47]
15 communities in the Akim districts

12200 (1100–42400) μgL⁻¹

Table 3: Period of data collection and analytical techniques.

Reference
Period of data collection
Region/community
Pollutant studied
Source of pollutant
Concentration of pollutants
Analytical Technique

Kortatsi et al. 2008 [66]
Not reported
Greater Accra region: 21 communities; Eastern region: 23 communities; Volta region: 44 communities
As
Water samples from 15 selected boreholes
See Tables  1–4
Wagtech Arsenator field test kit

Amonoo-Neizer et al. 1996 [19]
March 1992-1993
Ashanti region: Obuasi and its environ
As, Hg
Soil and food crops*, vegetation, and mud fish
See Tables II and III
As: UV-visible spectrophotometer A SPEKOL II
Hg: cold vapour atomic absorption spectrophotometer

Boadu et al. 2000 
[25]
Nov 1995, March 1996, July 1996, Nov 1996
Eastern region: Konongo and its surrounding towns and villages; Ashanti region: Odumase, Patriensa and Obenemase
As
Water sample from underground water, river, ponds of a river
See Tables  1 and 2
Instrumental neutron activation analysis

Serfor-Armah et al. 2001 [68]
June 1996–August 1998
Greater Accra region: Prampram, Nungua; Central region: Winneba, Cape Coast; and Western region: Sekondi, Axim
As, Al, Br, Fe, Mn, Cd, Hg, Zn, Ni, V, La
Seaweeds
See Tables III and IV
Neutron activation analysis

Asante et al. 2007 [15]
March 2004
Western region: Tarkwa and its environ
V, Cr, Mn, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, TI, Pb, Bi
Water samples from bore boles, wells, rivers/streams and urine samples
Bore hole and well water: <0.1–4.0 μg/L
Rivers/stream: 0.5–73 μg/L
Urine in mine workers: 34–650 μg/L and in non-workers: 43–700 μg/L
As: hydride generation atomic absorption spectrophotometer (HG-ASS);
Hg and Se: cold vapour atomic Absorption spectrometry;
Other metals: inductively coupled plasma mass spectrometry

Serfor-Armah et al. 2006 [28]
Jan 2002–April 2003
Western region: Prestea and its environ
As, Sb
Water samples from stream and soil sample
See Tables  2 and 3, Figures  3 and 4
Instrumental neutron activation analysis (INAA)

Rossiter et al. 2010 [69]
July/August 2007
Ashanti region (obuasi and its environs), North of the Volta region, Upper East region (Bolgatanga area)
Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se, U, V, Zn
Water samples from boreholes, wells and rivers
See Table  1
Inductively coupled plasma-optical emission spectroscopy (ICP-OES)

Basu et al. 2011 [57]
Summer 2009
Upper East region (Talensi-Nabdam district: Obuasi, World Bank, Kejitia)
Al, As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Zn
Urine sample
See Table  1
Inductively coupled plasma mass spectrometer (ICPMS)

Adokoh et al. 2011 [70]
Not reported
Western region: Pra Estuary-Shama
Central region: Benya Lagoon-Elimina; Fosu Lagoon-Cape Coast; Narkwa Lagoon-near Saltpong Beach
Al, As, Cd, Hg
Water and sediments samples
See Table  3
Neutron activation analysis

Armah et al. 2011 [65]
April 2010
Western region: Tarkwa mining area
As, Mn, Cd, Fe, Pb, Ni
Water samples from boreholes and taps
Table  1
Flame atomic absorption spectrophotometer

Armah et al. 2010 [5]
Feb–June 2009
Ashanti region (Obuasi and its environ)
As, Cu, Mn, Cd, Fe, Pb, Zn
Water samples from taps and surface water bodies
See Table  2
Flame atomic absorption spectrophotometer

Golow et al. 1996 [71]
Not reported
Ashanti region (Obuasi and its environ)
As
Soil samples from villages of varied distances from Obuasi Township
Figures  2 and 3
Schimadzu UV-120-02 spectrophotometer

Obiri et al. 2006 [72]
Not reported
Western region (Bogoso, Prestea, Tarkwa, Tamso)
Hg, Zn, Cd, As
Food crops: cassava, cocoyam, and other tuber crop samples
See Tables III, VII, VIII, XI
Schimadzu atomic absorption spectrophotometer

Essumang et al.
2007 [16]
Not reported
Western region: Tarkwa: Efuantah, Nsuta and Tamso
As, Cd, Hg
Food crop: cocoyam and water cocoyam samples
See Table  1
As, Cd: 
flame atomic absorption spectrophotometer
Hg: cold vapour technique

Obiri 2007 [64]
August 2004–June 2005
Western region: Dumasi in Wassa West District
As, Zn, Cd, Fe, Co, Cr, Pb, Mn
Water samples from boreholes
See Table  4
Flame atomic absorption spectrophotometer Shimadzu model coupled with an arsine gas generator

Adomako et al. 2011 [73]
Not reported
Selected supermarkets and markets in some regions in Ghana
As, Cd, Co, Cu, Mn, Pb, Se, Zn
Grains
See Figure  2
High performance liquid chromatography (HPLC)

Adomako et al. 2008 [74]
Jan to sept 2005: bimonthly sampling
Ashanti region/River Subin
Al, As, Cd, Cu, Cr, Zn
Water and sediment samples
Water sample 
Tables  3 and 4 
Sediment sample 
Tables  3 and 4
Neutron activation analysis

Amasa 1975 [31]
Not reported
Ashanti region (Obuasi and its environ)
As
Urine, Food crops, vegetation, soil, water samples
Tables  1 and 2
Neutron activation analysis

Golow and Adzei 2002 [75]
Not reported
Central region: Dunkwa-on-Offin
Zn
Soil and cassava tuber samples
Figures  2 and 3
AAS/Perkin-Elmer 51000 PV

Golow and Adzei 2002 [75]
Not reported
Central region: Dunkwa-on-Offin
Hg
Soil and cassava tuber samples
Figures  2 and 3
Cold vapour cell in AAS

Oppong et al. 2010 [32]
August 2005, Jan 2006
Central region: Awisam, Twifo Praso, Twifo Mampong
Western region: Daboaso, Beposo
Hg
Soil, sediments and, fish samples
Tables  1 and 2
Cold vapour atomic absorption spectrophotometer

Yidana et al. 2008 [76]
NA
Western region: Ankobra basin at Ankwaso, Dominase, Prestea
Hg, Mg
Water samples
Table  1
Not reported

Bentum et al. 2010 [77]
Not reported
Eastern region: Odumase-Atua area
Pb, As, Cd
Breast milk from lactating mothers
Pb: 4.83 ± 9.016 μg/L;
range: LOD-32.0 ± 1.935 μg/L
As: 1.54 ± 1.935 μg/L;
range: LOD-6.22 μg/L
Cd: 1.34 ± 2.194 μg/L
range: LOD-12.301 μg/L
Atomic absorption spectrophotometer (Philip AAS 9200u Model)

Essumang 2009 [55]
Not reported
Western region: Tarkwa
As
Human hair samples
0.0142–0.0515 μg/g
Inductively coupled plasma atomic emission spectrometer

Asante et al. 2007 [15]
March 2004
Western Region: Tarkwa and its environ
Cr, Mn, Co, Cu, Zn, Ga, As, Se, Rb, Sr
Water samples from boreholes, rivers/streams and urine sample of mine workers
Tables  1 and 2
Hydride generation-atomic absorption spectrophotometer

Abrefah et al. 2011 [58]
Not reported
Western region: mine workers at Tarkwa
As, Hg
Urine samples
As 
Distance from mine of workers
10 km: 6.76 ± 1.43 μg/L
2 km: 1.78 ± 1.33 μg/L
0.5 km: 8.03 ± 1.75 μg/L
Casual: 10.44 ± 1.88 μg/L
Gold ore workers:
14.75 ± 1.62 μg/L
Hg 
Distance from mine of workers
10 km: 0.36 ± 0.11 μg/L
2 km: 0.47 ± 0.12 μg/L
0.5 km: 0.51 ± 0.16 μg/L
Casual: 0.57 ± 0.14 μg/L
Gold ore workers:
0.56 ± 0.21 μg/L
Instrumental neutron activation analysis (INAA) for As;
¹⁹⁷Hg induced radionuclide in INAA for Hg

Kumi-Boateng 2007 [78]
Nov 2007 to Jan 2010 once/month
Ashanti region: Obuasi

Soil sample
Sediment sample
Soil sample
0–15 cm: 69.72 ppm;
15–30 cm: 42.90 ppm
Sediment sample
34 253 ppm
Atomic absorption spectrophotometer

Fianko et al. 2007 [61]
Weekly from Dec to June
Central region: Iture Estuary
Cd, Pb, Se, Zn
Water sample
See Figures  2–5, Table  6
Atomic absorption spectrophotometer

Basu et al. 2011 [57]
Summer 2009
Upper East region: Obuasi, World Bank, Kejitia
Al, As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Zn
Urine samples
See Table  1
Inductively coupled plasma mass spectrophotometer equipped with a quadrupole analyser and octopole collision

Kwaansa-Ansah et al. 2010 [60]
Not reported
Central region; Dunkwa-on-Offin area
Hg
Urine and hair samples
See Tables  1 and 2
Urine: cold vapour atomic absorption spectrometry using an automatic mercury analyser model HG 5000
Hair: open flask method

Paruchuri et al. 2010 [56]
May and June 2009
Upper East region
Bolgatanga
Hg
Urine and hair samples
Urine
170 ± 77.3 μg/g
(0.2–708)
Hair
0.1 ± 3.2 μg/g
(0.0–22.9)
Direct mercury analyzer

Adimado and Baah 2002 [35]
Not reported
Western region: Anwiaso; Sahuma, Tanoso, Elubo
Hg
Blood, urine, hair, nail, and fish samples
See Table  2
Atomic absorption spectrophotometer with flow injection mercury hydride system

Smedley 1996 [62]
Not reported
Ashanti region: Obuasi; Upper East region: Bolangatanga
Cr, Co, Ni, Cu, Zn, Y, Mo, Pb, Rb, Sb, Cs, U, Fe, As, Al
Water samples from boreholes
See Tables  1–10
Not reported

Amonoo-Neizer
and Amekor
1993 [14]
Not reported
Ashanti region: Kumasi and Obuasi area
As
Vegetation, cooked food, local fish, and meat (goat) samples
Kumasi: 0.07–7.20 mg/kg
Obuasi: 0.12–70.50 mg/kg

Amedjoe et al. 2012 [63]
June-July; Sept-Oct. 2010
Ashanti region: Homase area
Fe, Zn, As, Mg
Water samples from streams, hand-dug wells, borehole
See Tables  1 and 2
Not reported

Akabzaa et al.
2007 [24]
Not reported
Ashanti region: Obuasi mine
Fe, Mn, Cu, Ni, Zn, Pb, Cd, Hg, As
Water samples from streams, boreholes, hand-dug well
Tables  1 and 2
Not reported

Asante et al. 2012 [59]
Not reported
Greater Accra: Agbogbloshie area in Accra;
Ashanti region: Obuasi
V, Cr, Mn, Fe, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, Tl, Pb, Bi
Urine sample
Tables  1 and 2
All: metals: inductively coupled plasma mass spectrometer;
Hg: cold vapour atomic absorption spectrometer

Akabzaa et al.
2007 [24]
2002–2004
Ashanti region: Obuasi and its environ
Fe, Mn, Cu, Ni, Zn, Pb, Cd, Hg, As
Water samples from streams, boreholes, hand-dug wells, and fruit samples
See Tables  5.2–5.4
Atomic absorption spectrometry

Tay and Kortatsi 2008 [47]
Feb 2005–Dec 2005
Eastern and Greater Accra regions: 68 communities within Densu basin in these regions
Mg, Fe, Mn
Ground water samples
Tables  2a–2d
Not reported

Karikari and Ansa-Asare  2006 [79]
July 2003 and March 2004
Eastern region: Akwadum, Mangoase, Asuboi, Pakro and Ashalaji
Fe, Mn, Cu, Zn, Pb
Water sample from Densu river
Table  2
Atomic absorption spectrophotometer

Boamponsem et al. 2010 [29]
Sept 2008–Jan 2009
Western region: Teberebie, Mile 7 in the Wassa West District
Sb, Mn, Cu, V, Al, Co, Hg, As, Cd, Th
Water and sediments samples
Tables  2 and 3
Instrumental neutron activation analysis

Tay et al. 2010 [80]
Nov 2003 and Oct 2004
Greater Accra region: Sakumo II and Muni lagoons
Cu, Zn, Pb, Mn, Fe, Cd,
Water and sediments
Tables  1–4
Flame atomization

Kortatsi 2007 [81]
Not reported
Western region: Ankobra basin
Ag, Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sr, Th
Water samples from boreholes in the Ankobra Basin
Tables  1 and 2
ICP-MS

Dapaah-Siakwan
and Gyau-Boakye
2000 [82]
June 2002 to March 2003
Ashanti region: Obuasi
As, V, Th, Sb, U, Cr
Lichen samples
Table  2
As, Sb, U: epithermal instrumental neutron analyses
Cr, V, Th: thermal instrumental neutron analyses

Nartey et al. 2005 [83]
May-June and Sept to Novem each year
Eastern region: Akwapim area
Zn, Fe, Mn, Cu
Surface water samples from springs/streams
Table  2e
Flame atomic absorption spectrometer

Koranteng-Addo et al. 2011 [84]
Nov 2009 to Jan 2010
Western region: Tarkwa gold mining area
Cu, Zn, Fe, Mn
Sand and clay soil samples
Table  1
ICP-Atomic absorption spectrophotometer

Hayford et al. 2009[30]
Not reported
Western region: Tarkwa and its environs
As, Hg, Sb, V, Cu, Zn, Cr
Samples from cassava, plantain, and soil
Table  1
Instrumental neutron analyses

Ansa-Asare and Asante 2000 [85]
March, May, July, Sept, Nov 1995 and Jan 1996
Eastern region: Birim basin and its environ
Zn, Pb, Cu, Cd, Mn, Fe
Water sample from Birim basin and its environ
Table  4
Atomic absorption spectrophotometry (Varian 1275 AAS)

Bentum et al. 2011 [86]
Nov 2009
Central region: Cape coast
Fe, Cu, Zn, Pb, Al
Sediments sample from Fosu lagoon
Tables  3 and 4
Atomic absorption spectrophotometry (Varian 235 AAS)

Tay et al. 2008 [87]
Nov 2003 and Oct 2004
Greater Accra and Volta regions: James Town, Salaha, Tema Fishing harbour, Sogakope
Fe, Mn, Cu, Pb, Zn, Cd
Fish sample
Table  3
Flame atomization using Unican 969 Atomic absorption spectrophotometer

Nyarko et al. 2006 [34]
June 2002 and March 2003
Ashanti region: Obuasi and its environs
As, V, Th, Sb, U, Cr
Lichen samples
Tables  1 and 2
Neutron activation analysis

Dankwa and Biney
2005 [46]
Aug 1994
Central region: Kaniago, Buabuasin, Kubi, Baadoa and Twifu Praso
Hg, Cd, Pb, As, Cu, Zn, Mn, Fe
Sediment, fish, and water samples

Flame and cold atomic absorption spectrophotometry

Tay 2007 [67]
2002 and 2004
Volta region: Ketu and Akatsi
Mg, Fe, Mn
Water samples from boreholes

Atomic absorption spectrophotometry

Tay and Momade 2006 [26]

Ashanti region: Obuasi area
Ni, Hg, Pb, Mn, Fe, Cd
Water samples from borehole, well, and stream

Atomic absorption spectrophotometry

Donkor et al. 2006 [33]
July 2002
Central, western and Eastern regions: River Pra basins
Hg
Water samples from river pra basin

Ultraclean free-metal sampling protocol

Table 4: Levels of heavy metals in rivers/streams by region in Ghana.

(a)

Reference
Community
As
Hg
Fe
Mn
Cd
Zn
Cr
Cu
Pb

Ashanti region

Boadu et al. 2000 [25]
Rivers at Konongo and surrounding towns and villages: Odumase, Patrienso and Obenemase

River Owerri
271 (140–390) μgL⁻¹

River Awerekye
35 (30–40) μgL⁻¹

Tay and Momade 2006 [26]
10 streams in northern parts of Ashanti Gold belts

32 μgL⁻¹
115 μgL⁻¹

4.4 μgL⁻¹

6 μgL⁻¹

Dry season (Feb 2000)

660 (190–1330) μgL⁻¹
1080 (280–2,120) μgL⁻¹
185 (70–300) μgL⁻¹
9 (<1–13) μgL⁻¹

70 μgL⁻¹

90 μgL⁻¹

Wet season (June 2000)

320 (100–700) μgL⁻¹
1,150 (200–2,360) μgL⁻¹
20 (10–30) μgL⁻¹
44 (<1–70) μgL⁻¹

Akabzaa et al. 2007 [24]
Obuasi and its environ:
1891 μgL⁻¹
1.8 μgL⁻¹
1719 μgL⁻¹
285.4 μgL⁻¹
<0.2 μgL⁻¹
12 μgL⁻¹

8.6 μgL⁻¹
4.6 μgL⁻¹

4 rivers in communities within the operating area of AGC
1113 (<10–3071) μgL⁻¹
9.5 μgL⁻¹
2935 (358–5603) μgL⁻¹
693.7 (472–1525) μgL⁻¹
<2 μgL⁻¹
30.5 (14–69) μgL⁻¹

18.3 (2–27) μgL⁻¹
515 μgL⁻¹

3 rivers in communities immediately downstream
6452.5 (310–18910) μgL⁻¹
1 μgL⁻¹
6912.2 (259–17190) μgL⁻¹
913.4 (146–2584) μgL⁻¹
2 μgL⁻¹
39 (19–120) μgL⁻¹

35.3 (12–86) μgL⁻¹
105 μgL⁻¹

Akabzaa et al. 2007 [24]
Vicinity of Obuasi mine
3137 (9–18910) μgL⁻¹
8 (1–18) μgL⁻¹
5032 (259–17190) μgL⁻¹
758 (146–2584) μgL⁻¹
2 μgL⁻¹
34 (3–120) μgL⁻¹

23 (<0.1–86) μgL⁻¹
14 (1–57) μgL⁻¹

Adomako et al. 2008 [74]
River Subin
13.9 (07–160) μgL⁻¹

12.5 (2–50) μgL⁻¹
6600 (4280–10200) μg⁻¹
6 (10–19) μgL⁻¹
1330 (1320–7040) μgL⁻¹

Armah et al. 2010 [5]

434 μgL⁻¹; IQ-UQ (136–1135) μgL⁻¹
302 μgL⁻¹; IQ-UQ (2–646) μgL⁻¹
705 μgL⁻¹; IQ-UQ (242–1208) μgL⁻¹
892 μgL⁻¹; IQ-UQ (459–2152) μgL⁻¹
674 μgL⁻¹; IQ-UQ (418–1350) μgL⁻¹
139 μgL⁻¹; IQ-UQ (3–667) μgL⁻¹

603 μgL⁻¹; IQ-UQ (245–1831) μgL⁻¹
0.69 UQ (0.06–2.10) μgL⁻¹

Amedjoe et al. 2012 [63]

41 (39) μgL⁻¹

127 (98) μgL⁻¹

2 (1) μgL⁻¹

2.5 (2.3) μgL⁻¹

Western region

Serfor-Armah et al. 2006 [28]

384 (33) μgL⁻¹

Kortatsi 2006 [88]

300 (1000) μgL⁻¹
4600 (3700) μgL⁻¹
170900 (306500) μgL⁻¹
41900 (36400) μgL⁻¹

168000 (38700) μgL⁻¹
300 (100) μgL⁻¹
2400 (4100) μgL⁻¹
1100 (1400) μgL⁻¹

Asante et al. 2007 [15]

18 (0.5–73) μgL⁻¹

682 (11.1–2530) μgL⁻¹
0.04 (0.04–0.08) μgL⁻¹
138 (3.43–1500) μgL⁻¹
0.52 (0.10–1.2) μgL⁻¹
1.3 (0.97–9.17) μgL⁻¹
0.85 (0.02–3.71) μgL⁻¹

Asante et al. 2007 [15]

18 μgL⁻¹
BDL

682 μgL⁻¹
0.04 μgL⁻¹
138 μgL⁻¹
0.52 μgL⁻¹
2.65 μgL⁻¹
0.85 μgL⁻¹

Boamponsem et al. 2010 [29]
Tarkwa gold mining district

Angonabeng
1220 μgL⁻¹
148 μgL⁻¹

1780 μgL⁻¹
1110 μgL⁻¹

Bediabewu
52.2 μgL⁻¹
52.2 μgL⁻¹

804 μgL⁻¹
1110 μgL⁻¹

Adokoh et al. 2011 [70]

0.016 μgL⁻¹
0.002 μgL⁻¹

0.016 μgL⁻¹

Armah et al. 2011 [65]
Abunpuni
Angonabeng
Adisakrom
Bediabewu
Domeabra
Nkwantakrom
Teberebie
4 (4.1) μgL⁻¹

144 (279.2) μgL⁻¹
100 (228.3) μgL⁻¹
2 (2.9) μgL⁻¹

5.7 (0.3) μgL⁻¹

(b)

Reference
Community
Al
Ni
Co
V
Cr
Se
Sb
Sr
Mg
Rb

Western region

Serfor-Armah et al. 2006 [28]

14 (0.1) μgL⁻¹

Kortatsi 2006 [88]

12700 (47200) μgL⁻¹
1100 (1400) μgL⁻¹

100 (100) μgL⁻¹
300 (100) μgL⁻¹
300 (100) μgL⁻¹

27900 (22000) μgL⁻¹
7900 (4300) μgL⁻¹

Asante et al. 2007 [15]

1.3 (1.9) μgL⁻¹
0.46 (0.57) μgL⁻¹
0.52 (0.34) μgL⁻¹

214 (359) μgL⁻¹

4.65 (3.68) μgL⁻¹

Asante et al. 2007 [15]

1.3 (0.05–6.9) μgL⁻¹
0.46 (0.02–2.0) μgL⁻¹
0.52 (0.10–1.2) μgL⁻¹
BDL
2.0 (<0.01–15) μgL⁻¹
214 (22.6–2240) μgL⁻¹

4.65 (1.93–15.5) μgL⁻¹

Boamponsem et al. 2010 [29]
Tarkwa gold mining district

Angonabeng

409 μgL⁻¹
37 μgL⁻¹

4140 μgL⁻¹

Bediabewu

230 μgL⁻¹
37.8 μgL⁻¹

1070 μgL⁻¹

Adokoh et al. 2011 [70]

0.964 μgL⁻¹

Armah et al. 2011 [65]
Abunpuni
Angonabeng
Adisakrom
Bediabewu
Domeabra
Nkwantakrom
Teberebie

0.4 (0.3) μgL⁻¹

(c)

Reference
Community
μgL⁻¹

As
Hg
Fe
Mn
Cd
Zn
Cr
Cu
Pb

Eastern region

Karikari and Ansa-Ansare 2006 [79]
Densu Basin covering Akwadum, Mangoase, Asuboi, Pakro and Ashalaja

964 (614–1190)
291 (264–337)

57 (14–100)

80 (28–274)
18 (<5–39)

Ansa-Asare and Asante 2000 [85]

61.4 (5–157)
60.7 (2–263)
1.4 (<1–2.6)
68.6 (1–89.2)

1.4 (0.1–2.6)

Boadu et al. 2000 [25]
Konongo and its surrounding areas: Odumase, Patriensa, Obenemase

River Owerri
27.3 (13–43)

River Awirekye
3.5

Nartey et al. 2005 [83]
Seven streams in the Akwapim Ridge (Otobri, Kobi, Opiafo, Amankrate, Kwati, Ademi, Elemi)

714.3
614.3

200

Central region

Dankwa and Biney 2005 [46]

2.09

<0.01

0.47

Donkor et al. 2006 [33]

20536

Fianko et al. 2007 [61]
Rivers supplying water to Iture Estuary

Sorowie

4
180

6.45

Kakum

3.2
200.1

2.65

Boamponsem et al. 2010 [29]
Kakum
1

145

Adokoh et al.   2011 [70]
Benya Lagoon
0.106
0.003

1.706
0.051

Fosu lagoon

0.002

1.477
0.036

Narkwa Lagoon
0.068
0.002

1.112
0.0425

Bentum et al. 
2011 [86]
Fosu Lagoon

1150
2230

20.9

26.4

Tay et al. 2010 [80]
Greater Accra

1.65 (0.20)
0.942 (0.06)
0.006 (0.001)
0.113 (0.010)

0.268 (0.06)
0.02 (0.0)

Table 5: Metals in food, sediment, and fish by region in Ghana.

(a)

Reference
Region/community
Source of pollutants studied
 As (mgkg⁻¹)
 Hg (mgkg⁻¹)

 As (mgkg⁻¹)
 Hg (mgkg⁻¹)

 As (mgkg⁻¹)
 Hg (mgkg⁻¹)

Ashanti region

Amasa 1975 [31]
Obuasi and its environ

Soil
19.30 (11.75–2875.0)

cassava
1.09 (0.83–2.65)

Cocoyam
2.16 (1.89–4.80)

Plantain
0.62 (0.60–0.63)

Orange
2.29

Sugar cane
14.75 (14.54–14.96)

Palm tree
2875 (2850–2900)

Fern
2729 (1100–4700)

Bananas
13.46 (11.6–20.9)

Amonoo-Neizer et al. 1996 [19]
Obuasi and its environ:

Villages up to about 2 km from Pompora Treatment Plant (PTP)

Villages up to about 5 km from Pompora Treatment Plant (PTP)

Villages up to about 9 km from Pompora Treatment Plant (PTP)

Soil
24.76 (23.6–48.9)
0.56 (0.4–0.7)

3.09 (2.7–3.7)
0.66 (0.66–1.2)

2.61 (2.4–3.3)
0.6

Plantain
3.40 (3.1–4.3)
0.78 (0.70–1.5)

1.49 (1.4–1.7)
0.6 (0.38–0.9)

1.02 (1.0–1.4)
0.11 (0.1–0.4)

Cassava
2.6 (1.9–3.3)
1.1 (0.9–1.3)

1.21 (1.0–1.3)
0.40 (0.3–0.5)

1.04 (0.8–1.5)
0.2

Mud fish

0.42 (0.3–0.9)
0.32 (0.2–0.8)

0.56 (0.5–0.7)
0.24 (0.1–0.4)

Fern
23.9 (22.8–78.7)
2.57 (2.4–2.6)

3.79 (3.2–30.4)
3.33 (1.8–4.4)

3.83 (2.8–27.8)
1.39 (1.2–4.1)

Elephant grass
15.2 (14.3–15.6)
3.20 (3.0–3.4)

1.5 (0.9–2.1)
1.1 (0.7–1.5)

Villages up to about 4 km from Pompora Treatment Plant (PTP)

Villages up to about 7 km from Pompora Treatment Plant (PTP)

Villages > 9 km from Pompora Treatment Plant (PTP)

Soil
3.66 (2.9–30.7)
0.74 (0.3–1.4)

2.79 (2.4–3.6)
1.34 (1.3–2.5)

2.52 (2.1–2.79)
0.56 (0.4–1.2)

Plantain
1.53 (1.4–3.6)
0.13 (0.1–1.4)

1.35 (1.1–1.6)
0.25 (0.2–0.7)

0.9 (0.5–1.32)
0.41 (0.3–2.1)

Cassava
1.26 (1.1–2.5)
0.22 (0.2–1.8)

0.91 (0.8–1.1)
0.59 (0.5–0.8)

0.89 (0.7–1.0)
0.34 (0.2–2.5)

Mud fish
0.45 (0.3–2.7)
0.47 (0.2–2.0)

0.48 (0.4–1.2)
0.22 (0.2–0.6)

0.57 (0.5–0.6)
0.42 (0.4–0.9)

Fern
5.35 (3.2–50.2)
3.61 (2.1–9.7)

3.53 (2.7–4.5)
1.7 (1.3–2.1)

2.33 (2.1–24.5)
2.6 (2.0–8.0)

Elephant grass
3.02 (2.0–27.4)
0.38 (0.2–1.8)

1.43 (1.41–1.57)
1.28 (1.0–1.9)

6.5 (6.0–8.0)
5.3 (4.7–5.9)

(b)

Reference
Region/community
Source of pollutants studied
(mgkg⁻¹)

As
Hg
Fe
Mn
Cd
Zn
Cr
Cu
Ni
Pb

Ashanti region

Akabzaa et al. 2007 [24]
Obuasi and its environ:
Sediments

Communities within the operating area of AGC

1332.26 (0.25–7591.58)
0.83 (0.28–3.02)
34406 (6220–50,180)
47.15 (2.76–167.24)

29.73 (8.87–80.35) mgkg⁻¹

25.25 (3.65–80.46)
10.33 (3.28–23.11)
0.65

Communities immediately downstream

2984.27 (190.38–5778.15)
2.02 (1.44–2.6)
19810 (13910–25710)
15.22 (12.72–24.55)
0.24
102.13 (61.74–142.55)

45.86 (41.44–50.27)
10.22 (8.36–12.08)
60.04 (4.71–115.37)

Fruits
4.94
0.023
1.71
0.379
0.083
16.55

0.55

0.072

Communities within the operating area of AGC

4.94 (0.02–12.26)
0.023 (0.02–0.026)
1.71 (0.21–4.11)
0.38 (0.27–0.56)
0.09 (0.04–0.13)
16.55 (7.4–24.30)

0.55 (0.40–0.84)

0.072

Adomako et al. 2008 [74]
Sediment in Subin River in Kumasi/Ashanti region
Sediments
3.43 (2.34–7.65)

1.06 (0.28–1.42)
18.50 (14.40–98.30)
30.57 (18.50–136.40)
3.32 (3.11–12.63)

Golow et al. 1996 [71]
Obuasi mining area
Top soil
33.3 (25–45)

Golow et al. 1996 [71]
Obuasi mining area
Fish
0.45 ± 0.12
0.47 ± 0.05

Nyarko et al. 2006 [34]
Obuasi gold mining area
Lichens
60.95 (6.80–196.0)

6.60 (1.80–14.0)

(c)

Reference
Region/community
Source of pollutants studied
 Sb (mgkg⁻¹)
 V (mgkg⁻¹)
 Th (mgkg⁻¹)

Ashanti region

Amonoo-Neizer and Amekor 1993 [14]
Obuasi area
Uncooked food

cassava
2.55 (1.85–3.25)

Cocoyam
2.26 (1.36–3.18)

Plantain
3.43 (2.36–4.5)

Pepper
2.96 (2.05–3.87)

Orange
3.46 (3.10–3.91)

Beans
0.99 (1.21–0.77)

Pear
1.59 (0.97–2.21)

Cooked food

Cassava
2.67

Plantain
3.39

Fufu
2.37

Oil Palm fruit
3.03

Star grass
6.67

Elephant grass
4.85

Amonoo-Neizer and Amekor 1993 [14]
Kumasi area
Uncooked food

cassava
1.03 (0.84–1.87)

Cocoyam
0.97 (0.81–1.13)

Plantain
1.10 (0.85–1.35)

Pepper
0.58 (0.5–0.66)

Orange
0.85 (0.45–1.25)

Beans
0.52 (0.42–0.62)

Pear
0.76 (0.9–0.62)

Cooked food

Cassava
1.91

Plantain
3.03

Fufu
1.4

Oil Palm fruit
3.5

Tobacco
2.14

Cocoa
2.44

Star grass
6.67

Elephant grass
4.85

Nyarko et al. 2006 [34]
Obuasi gold mining area
Lichen

27.63 (2.90–74.80)
1.08 (0.13–4.44)

Serfor-Armah et al. 2006 [28]
Prestea and its environ
Sediment
12.46 (8.50–90.40)

Hayford et al. 2009 [30]
Tarkwa and its environs
Soil
2.98
188.40

Cassava
0.03
0.8

Plantain
0.02
0.42

Boamponsem et al. 2010 [29]
Angonabeng
Sediment
38.9
133
1.64

Bediabewu
Sediment
309
417
15.72

(d)

Reference
Region/
community
Source of pollutants studied
 As
 Hg
 Fe
 Mn
 Cd
 Zn
 Cr
 Cu
 Ni
 Pb

Western region

Donkor et al. 2006 [33]
Lower Pra river basin
River sediments

25.89 (6.52–57.32) mgkg⁻¹

Soil

75.61 (3.40–202.32) mgkg⁻¹

Serfor-Armah 
et al. 2006 [28]
Prestea and its environ
Sediments
2261.8 (942–10,200) mgkg⁻¹

Essumang et al. 2007 [16]
Food crops from Efuantah, Nsuta and Tamso in Tarkwa district
Cocoyam

Water cocoyam
146 mgkg⁻¹ 

383.5 mgkg⁻¹ 

3 mgkg⁻¹ 

3.5 mgkg⁻¹ 

43 mgkg⁻¹ 

181.5 mgkg⁻¹ 

Hayford et al. 2009 [30]
Tarkwa and its environs
Soil
0.7 mgkg⁻¹
0.25 mgkg⁻¹

38.42 mgkg⁻¹
0.72 mgkg⁻¹
66.39 mgkg⁻¹

Cassava
0.43 mgkg⁻¹
0.41 mgkg⁻¹

26.62 mgkg⁻¹
0.44 mgkg⁻¹
33.61 mgkg⁻¹

Plantain
0.34 mgkg⁻¹
0.36 mgkg⁻¹

18.87 mgkg⁻¹
2.2 mgkg⁻¹
5.44 mgkg⁻¹

Boamponsem  et al. 2010 [29]
Sediments in 5 streams in Tarkwa gold mining district
Sediments

Angonabeng

5.41 mgkg⁻¹
0.212 mgkg⁻¹

36468 mgkg⁻¹
0.658 mgkg⁻¹

13 mgkg⁻¹

Bediabewa
“
13.4 mgkg⁻¹
0.054 mgkg⁻¹

365 mgkg⁻¹
0.312 mgkg⁻¹

20.1 mgkg⁻¹

Mile 7 spring

1.65 (1.15–2.22) mgkg⁻¹

55.9 (42.1–69.7) mgkg⁻¹

2.92 mgkg⁻¹

Teberebie spring 2

1.94 (0.94–2.94) mgkg⁻¹
0.06 mgkg⁻¹

189.2 (134.3–244.1) mgkg⁻¹
0.20 mgkg⁻¹

230.2 mgkg⁻¹

Teberebie spring 3

1.06 (0.79–1.33) mgkg⁻¹
0.01 mgkg⁻¹

117770 mgkg⁻¹
0.43 mgkg⁻¹

1201 mgkg⁻¹

Oppong et al. 2010 [32]
Soil, sediments and fish from the River Pra Basin at Daboaso, Beposo, Twifo Praso and Twifo Mampong

Daboase

Sediment

0.707 mgkg⁻¹

Soil

0.075 mgkg⁻¹

Fish

0.166 mgkg⁻¹

Beposo

Sediment

0.575 mgkg⁻¹

Soil

0.145 mgkg⁻¹

Fish

0.153 mgkg⁻¹

Adokoh et al. 2011 [70]
Sediments in Pra Estuary at Shama
Sediment
0.016 mgkg⁻¹
0.017 mgkg⁻¹

Koranteng Addo et al. 2011 [84]
Abandoned open pit in the Tarkwa mining district
Sand

53151.28 (145–119,166) mgkg⁻¹
34.45 (26.67–1595) mgkg⁻¹

21.06 (4.17–43.17) mgkg⁻¹

12 (6.5–56.17) mgkg⁻¹

Clay

71013.08 (67,000–134,833.3) mgkg⁻¹
56.76 (36.16–147.3) mgkg⁻¹

20.35 (15–27.67) mgkg⁻¹

13.56 (9.17–21.83) mgkg⁻¹

(e)

Reference
Region/
community
Source of pollutants studied
 As
 Hg
 Fe
 Mn
 Cd
 Zn
 Cu
 Al
 Pb

Central region

Golow et al. 1996 [71]
Dunkwa-on-Offin

Top soil (0–5 cm deep)

153.75 mgkg⁻¹

Cassava leaves

15.63 mgkg⁻¹

Cassava flesh

6.5 mgkg⁻¹

Golow and Adzei 2002 [75]
Dunkwa-on-Offin

Top soil (0–5 cm deep)

41.75 mgkg⁻¹

Cassava leaves

13.75 mgkg⁻¹

Cassava flesh

100 mgkg⁻¹

Dankwa and Biney 2005 [46]
Five sites in Offn river basin: Kaniago, Buabuasin, Kubi, Baadoa, Twifo-Praso
Bottom sediment
<500 mgkg⁻¹
<200 mgkg⁻¹
15.75 × 10⁶ mgkg⁻¹
1800 mgkg⁻¹
<200 mgkg⁻¹
12900 mgkg⁻¹
<200 mgkg⁻¹

Fish fauna

Brycinus nurse R
<300 mgkg⁻¹
320 mgkg⁻¹
3760 mgkg⁻¹
500 mgkg⁻¹
<100 mgkg⁻¹
2560 mgkg⁻¹
300 mgkg⁻¹

250 mgkg⁻¹

Chrysichthys nigrodigitatus L
<300 mgkg⁻¹
230 mgkg⁻¹
3310 mgkg⁻¹
570 mgkg⁻¹
<100 mgkg⁻¹
570 mgkg⁻¹
2500 mgkg⁻¹

440 mgkg⁻¹

Tilapia zillii G
<300 mgkg⁻¹
60 mgkg⁻¹
2660 mgkg⁻¹
1350 mgkg⁻¹
<100 mgkg⁻¹
1820 mgkg⁻¹

70 mgkg⁻¹

Donkor et al. 2006 [33]
Offin river basin
River sediments

23 (2.73–49.86) mgkg⁻¹

Soil

263.79 (1.56–2146.96) mgkg⁻¹

Boamponsem et al. 2010 [29]
Kakum
Sediments
1.31 mgkg⁻¹

777 mgkg⁻¹

3.21 mgkg⁻¹
15836 mgkg⁻¹

Adokoh et 
al. 2011 [70]
Benya Lagoon-Elimina; Fosu Lagoon-Cape Coast; Narkwa Lagoon-near Saltpong Beach
Fosu Lagoon

Sediments
0.529 mgkg⁻¹
0.014 mgkg⁻¹

0.526 mgkg⁻¹

56.453 mgkg⁻¹

Narkwa Lagoon

Sediments
0.603 mgkg⁻¹
0.008 mgkg⁻¹

0.041 mgkg⁻¹

17.925 mgkg⁻¹

Benya Lagoon

sediment

60.407 μgg⁻¹

Bentum et al. 2011 [86]
Fosu Lagoon
Sediments

1150 mgkg⁻¹

20.9 mgkg⁻¹
26.4 mgkg⁻¹
2230 mgkg⁻¹
28.1 mgkg⁻¹

(f)

Reference
Region/community
Source of pollutants studied
 As
 Hg
 Fe
 Mn
 Cd
 Zn
 Cr
 Cu
 Ni
 Pb

Greater Accra region

Tay and Kortatsi 2008 [47]

Shell fish

20.92 (9.68–35.04) mgkg⁻¹
22.08 (7.27–22.16) mgkg⁻¹
0.26 (0.11–0.34) mgkg⁻¹
13.52 (6.55–16.09) mgkg⁻¹

1.36 (0.87–7.73) mgkg⁻¹

0.084 (0.08–0.44) mgkg⁻¹

Fin fish

14.95 (0.75–23.18) mgkg⁻¹
0.036 (0.03–19.37) mgkg⁻¹
0.081 (0.08–0.14) mgkg⁻¹
11.13 (6.2–19.19) mgkg⁻¹

0.244 (0.1–14.18) mgkg⁻¹

0.754 (0.9–1.09) mgkg⁻¹

Tay et al. 2010 [80]
Sakumo II and Muni lagoons
Sediment

3208.6 (563.2–7486.9) mgkg⁻¹
298.21 (63.7–668.2) mgkg⁻¹
0.70 (<0.25–0.88) mgkg⁻¹
155.2 (10.4–155.2) mgkg⁻¹

37.4 (3.79–37.4) mgkg⁻¹

3.6. Levels of Heavy Metals in Riverine Sediments and Soil

There was a high degree of variability in metal concentrations in riverine sediments and soil reported by the studies reviewed (Table 4). The lowest concentration of As in sediment was reported by Akabzaa et al. [24] for the Anglogold Ashanti area in Obuasi and the highest As concentration (10,200 mgkg⁻¹) was reported by Serfor-Armah et al. [28] for Prestea in the Western region of Ghana. The lowest concentration of Hg (0.01 mgkg⁻¹) was reported by Boamponsem et al. [29] for Teberebie spring 3 in the Tarkwa gold mining area. Also, Boamponsem et al. [29] reported the highest concentration of Hg (200 mgkg⁻¹) for bottom sediments of the Offin River basin. The highest concentration of Pb (115 mgkg⁻¹) was reported by Akabzaa et al. [24] for communities immediately downstream of the Anglogold Ashanti mine in Obuasi.

Generally, heavy metal concentrations in soil reported by the studies reviewed were higher than metal concentrations in riverine sediments. Studies reviewed did not report on Mn, Ni, or Pb concentrations in soil. The lowest As concentration (0.7 mgkg⁻¹) in soil was reported by Hayford et al. [30], whereas the highest As concentration (2875 mgkg⁻¹) in soil was reported by Amasa [31]. The lowest concentration of Hg (mgkg⁻¹) in soil was reported by Oppong et al. [32] for the Pra River basin at Daboase, Western Ghana. The highest concentration of Hg (2146 mgkg⁻¹) was reported by Donkor et al. [33] for the Offin River basin.

3.7. Levels of Heavy Metals in Fruits, Vegetables, and Edible Plants

Generally, studies reviewed focused mainly on the chemical content of certain elements in the biologic specimen. None focused on the influence of heavy metals on the morphological or cellular structure or metabolic-biochemical processes in the biologic specimen. Some of the studies categorised the food items analysed into cooked and uncooked (e.g., [14]), whereas others did not distinguish between the cooked and uncooked forms [24]. Only one study [34] reported on heavy metals using lichens as biologic specimen in the Obuasi gold mining area. Similarly, one study [14] used star grass as biologic specimen. However, two studies [19, 31] used ferns and two other studies [14, 19] used elephant grass as biologic specimen. Several fruits and vegetables were used in the studies reviewed as biologic specimen. The vegetables include pepper, beans, cocoyam, cassava, and plantain. Fruits include oil palm, cocoa, sugar cane, pear, orange, and banana.

Amasa [31] reported very high concentration of As in ferns (up to 4700 mgkg⁻¹) and oil palm (2900 mgkg⁻¹). The lowest As concentrations were reported for plantain (2.29 mgkg⁻¹) and cassava (2.65 mgkg⁻¹) in Obuasi and its environs (Tables 5(a)–5(e)). Generally, the magnitude of As concentrations in soil and biologic specimen in decreasing order as reported by the studies reviewed was as follows: palm tree > fern > soil > sugar cane > banana > orange > cocoyam > cassava > plantain. Essumang et al. [16] reported As concentrations as high as 383 in water cocoyam grown in soils of the Tarkwa gold mining area. The magnitude of Hg concentrations in soil and biologic specimen in decreasing order as reported by the studies reviewed was as follows: fern > soil > elephant grass > plantain > cassava.

3.8. Levels of Heavy Metals in Urine and Blood

Studies reviewed broadly reported heavy metals concentrations in urine for gold mine workers, non-gold mine workers, and workers exposed to fumes from e-waste recycling. Urine was the most common biological marker of heavy metal exposure used by the studies reviewed. Generally, reports on the levels of heavy metals in gold mining workers and their non-gold mining counterparts did not reveal any discernible pattern. For instance, from Asante et al. [15] it can be deduced that the non-mine worker/mine worker ratios for As, Hg, Mn, Cd, Zn, Cr, Cu, and Pb were 1.2, 10.9, 1.3, 7.7, 0.3, 3.7, 1.4, and 1.2, respectively. This suggests that except Zn non-mine workers generally had lower concentrations of heavy metals in their urine compared to their counterparts who were mine workers. This result is counter-intuitive. Heavy metals in urine samples of small scale artisanal gold miners in the Upper East region did not differ significantly from heavy metals in urine samples of e-waste recyclers in Accra. Only one study [35] reported on heavy metals in blood samples mostly in some residents in the Western region of Ghana. Mercury levels in such residents varied spatially. For instance, Adimado and Baah [35] reported Hg concentrations of 218 μgL⁻¹ and 57 μgL⁻¹ for residents in Bibiani Anhwiaso Bekwai and Tanoso, in south western Ghana.

3.9. Levels of Heavy Metals in Hair and Nails

Hair was the second most common biological marker of heavy metal exposure used by the studies reviewed unlike nails, which were sparingly used. Generally, concentrations of heavy metals reported by the studies reviewed for nails were higher than for hair. One study [35] reported higher concentrations of heavy metals in nails than in hair.

4. Discussion

In this review, we provide a systematic categorisation of the results of studies published from 1975 to January 2013 on As, Hg, Cd, Zn, Sb, Cr, Fe, Co, Cu, Ni, Zn, Mn, and Pb levels in water, soil, sediment, fruits, and vegetables as well as human hair, urine, blood, and nails in Ghana. We found that the use of vegetables, fruits, fish, hair, nails, and blood as biomarkers of exposure to heavy metals is not appropriately developed because of the heterogeneity among the studies. This heterogeneity applies not only to the populations selected and the analytical techniques (as it impinges on accuracy and precision) but also to the processing of specimens and presentation of results. The procedure for collection, pretreatment, storage, and preparation of the heavy metals prior to analysis varied extensively among studies, although available data suggest that such processes may influence the magnitude and comparability of the trace metal concentrations [36, 37].

It would appear that large variability in measured concentrations, apart from collection methods as mentioned above, was likely the result of differences in spatial characteristics of the sampling locations. Similarly, for the published studies that focused on human subjects, the variability in measured concentrations may emanate from varying excretion profiles amongst widely varying individuals with ranges of body burdens, genetic polymorphisms affecting detoxification efficiency, and physiological states [38]. These variations were very much greater than would be expected due to limitations of analytical methods. Although analytical methods have improved over the years, analysis of these metals was routine at the time of the studies.

Apart from geogenic sources, the contamination chain of heavy metals emanating from anthropogenic sources almost always follows a cyclic order: industry, atmosphere, soil, water, foods, and humans [39]. Regarding exposure to contaminants in environmental media, surface and groundwater were the most studied. Published results clearly indicate widespread contamination of ground and surface water especially in gold mining environments. Groundwater quality in natural systems is a result of many environmental factors. Climate, geology, biochemistry, composition of atmospheric precipitation, and the nature of the hydrology are among the more important factors [39].

Arsenic concentrations in aquifers in different geologic settings vary considerably over short distances. In the mining communities the geologic settings are Tarkwaian or Birimian systems [40]. Arsenic in groundwater occurs in two species (chemical forms), As (III) and As (V), which denote the As oxidation state. Arsenic (V) consists of arsenic acid (H₃AsO₄) and its conjugate bases (H₂As, HAs, and As). In the pH range of most natural waters, the predominant As (V) species are the anions H₂As and HAs [39]. In the same pH range, As (III) consists of mostly uncharged arsenious acid (H₃AsO₃) with a minor amount (<10%) of the anion H₂As which sorbs As (III) [39, 41]. The predominant As species in groundwater in the mining communities (i.e., Bogoso, Tarkwa, Teberebie, Damang) is As (III), which is obtained from the oxidation of FeAsS (arsenopyrite) ore abundant in these communities [40]. Most of ingested arsenic is rapidly excreted via the kidney within a few days. However, high levels of arsenic are retained for longer periods of time in the bone, skin, hair, and nails of exposed humans [36].

Iron concentration in groundwater varied extensively with location. The inconsistent value of Fe obtained in this study is not unexpected owing to the high occurrence of the metal in nature. Fe constitutes a high weight percentage in sulphide ores and is therefore likely to be very high, at areas of active metallurgic activity such as Tarkwa, Damang, and Bogoso. According to Kelly et al. [41], in wells for which the total organic carbon (TOC) concentration is less than ~2 milligrams per liter (mg/L), As is usually undetectable (<1 μg/L). For wells with higher TOC values, high As concentrations are more likely. In wells with detectable sulfate, As is almost always undetectable, while wells with undetectable sulfate may have high As concentrations. A likely explanation is that As is associated with iron oxide coatings on sand grains in the aquifer [39]. In areas where organic carbon is abundant, the iron oxide gets reduced and the As is released to the groundwater. In areas with abundant sulfate, sulfate reduction forms ferrous sulfide (FeS), and the predominant As (V) species are the anions H₂As and HAs [39, 42].

Levels of Cd in groundwater demonstrated that weathering of calcareous rocks was sufficient to provide the amounts of Cd found in the water profiles. In addition, the input of Cd by weathering was larger than the input by anthropic or geogenic atmospheric depositions which are the only other potential sources of Cd in mining areas. Several published studies reviewed reported Cd in human hair and nails. Cadmium accumulates in the human body adversely affecting a number of organs: liver, kidney, lung, bones, placenta, brain, and the central nervous system [43]. According to Apostoli and Catalani [44], other cadmium-related health effects that have been observed include reproductive, and development toxicity, hepatic, haematological and immunological effects.

According to Morais et al. [36], tobacco smoke is one of the largest single sources of cadmium exposure in humans. Eugenio Figueroa [45] argues that given the fact that the absorption of cadmium from the lungs is much greater than from the gastrointestinal tract, smoking contributes significantly to the total body burden. On the whole, for nonsmokers and non-occupationally exposed workers, food products comprise most of the human exposure burden to cadmium [36]. Some of the published studies reviewed reported Cd in a variety of food items including fruits [24], cocoyam [16], and shell and fin fish species [46, 47]. In food, only inorganic cadmium salts are present. Organic cadmium compounds are very unstable. Unlike lead and mercury ions, cadmium ions are readily absorbed by plants. They are evenly distributed over the plant. It is widely known that cadmium is taken up through the roots of plants to edible leaves, fruits, and seeds. In fact, during the growth of grains such as wheat and rice, cadmium taken from the soil is concentrated in the core of the kernel [45]. Cadmium also accumulates in animal milk and fatty tissues [45]. Therefore, individuals are exposed to cadmium when eating plant- and animal-based foods. As argued by Castro-González and Méndez-Armenta [43] seafood, such as molluscs and crustaceans, can be also a source of cadmium.

The principal controls on manganese concentration in groundwater are pH (acidity) and redox (oxidation-reduction) condition. Manganese is mobilised under acidic conditions. Hence concentrations can be relatively high in acidic waters such as some industrial waters and those issuing from mines rich in weathered sulphide minerals. This resonates with the situation in the mining areas under study. In pH-neutral conditions, the mobility of manganese is determined by ambient redox conditions. Under anaerobic conditions, manganese is reduced to the more soluble form, Mn(II), which is released from minerals. As a result, much higher manganese concentrations can be found in anaerobic ground waters.

The highest maximum dissolved Pb concentrations were found in water samples from surficial aquifer systems, which is not surprising given the highly corrosive conditions (typically low pH, high DOC concentrations, and low dissolved oxygen levels). Lead most likely is transported in ground water by mobile particulate matter [48]. Erel et al. [49] estimate that up to 15 percent of the industrial Pb deposited from atmospheric deposition is incorporated in water that infiltrates through soils to ground water. Other studies have demonstrated a downward migration of Pb through soils and into aquifers, which depends on the mobility of organic matter and sesquioxides because of the high stability of Pb-organic matter and Pb-sesquioxide complexes [50]. Any dissolved Pb that is present (e.g., low pH waters) in ground water would tend to form complexes with several anionic ligands and the migration of dissolved Pb in ground water would be dependent on its form (the predominant Pb species) in solution. For example, free divalent Pb ion (Pb²⁺), which is the predominant species of Pb in low-ionic strength waters, tends to sorb on negative sites of clays and other minerals and aquifer materials [51]. Lead concentrations in ground water are related to differences in chemical conditions among aquifers and aquifer systems. In humans, lead ingestion may arise from eating lead contaminated vegetation or animal foods. Another source of ingestion is through the use of lead-containing vessels or lead-based pottery glazes [36].

It is not always that existence of these metals in humans should be considered as toxic. In higher animals and humans, the proven micronutrients include Cr, Cu, Fe, Mn, and Zn. There is even some evidence that Cd, Pb, and Sn may be essential at very low concentrations [4, 52, 53] although this evidence is disputed by Vieira et al. [54] and Morais et al. [36]. However, the micronutrients which have been conclusively proven to be essential in animal and/or human nutrition and whose concentrations in diets are critical are Co (ruminants only), Cr, Cu, Fe, Mn, and Zn [4].

Published results on the levels of heavy metals in mine and non-mine workers yielded contradictory results. Mine workers were anticipated to have higher levels of heavy metals than their non-mining counterparts, but published results did not support this expectation. In fact, two of the studies reviewed found evidence to the contrary.

5. Conclusions

There is a plethora of environmental issues and concerns on which many scientists have focused their research in past years. In Ghana, tremendous efforts have been mobilized to evaluate the nature, presence, magnitude, fate, and toxicology of anthropogenic-induced heavy metals in diverse environments. The scope of this list is quite broad, encompassing environmental events locally, regionally, and nationally. Heavy metals affect aquatic and terrestrial ecosystems and biotic and abiotic environments and impacts on plants, humans, and wildlife, and virtually all environmental media (soil, water, and air). The staggering volume of scientific literature (during the last half century) on heavy metal contamination of environmental media and biota in mining and non-mining environments in Ghana demands remedy by which data can be synthesized. There is thus an urgent need to provide the coherency essential for nonduplicative and current progress in this field which is dynamic and complex. This systematic review attempts to address this need and provides a systematic categorisation of the results of studies published from 1975 to January 2013 on As, Hg, Cd, Zn, Sb, Cr, Fe, Co, Cu, Ni, Zn, Mn, and Pb levels in water, soil, sediment, fruits, and vegetables as well as human hair, urine, blood, and nails in Ghana.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

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