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GEOLOGY, ECOLOGY, AND LANDSCAPES INWASCON https://doi.org/10.1080/24749508.2021.1952775 RESEARCH ARTICLE Mineralogy and geochemistry of geophagic materials at Mfensi-Adankwame in the Ashanti region of Ghana and possible health implications a b c Rasheed Mohammed Abdul , Emmanuel Arhin and Atta Adjei Arhin Jnr Department of Geology, Pan African University Institute of Life and Earth Sciences (Including Health and Agriculture) (PAULESI), University of Ibadan, Ibadan, Nigeria; Faculty of Earth and Environmental Sciences, Department of Earth Science, University of Technology and Applied Sciences, Navrongo, Ghana; Department of Geological Engineering, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana ABSTRACT ARTICLE HISTORY Received 21 October 2020 Geophagia is widespread in rural Ghana and particularly among pregnant and breastfeeding Accepted 4 July 2021 women. The perceptions of the practitioners to ingest the geophagic materials generally are not based on science and data but are hinged often on cultural and traditional beliefs and KEYWORDS sometimes thought as substitute to treat some ailments without the use of medicine. The Earth products; Aqua Regia; geophagic materials are earth products and could contain essential and harmful elements as trace element; stomach well as materials that may have detrimental impact to human health. To assess the health risks disorder; sigmoid colon accompanying the consumption of geophagic material, twenty geophagic materials were analyzed geochemically using Ultra Trace Aqua Regia ICP-MS analytical technique and with Qualitative X-Ray Diffraction analysis (XRD Qual) for the mineralogical phases. The results revealed quartz as the abundant mineral (average, 54.30%). The chemical analysis also revealed depletions of the analyzed elements. The health risk assessment showed the practitioners risk consuming the geophagic materials because the health risk indices for Pb and Cr were >1. Again, the substantial amount of quartz in the geophagic materials may damage the dental enamel during mastication and as well erode the gastro-intestinal lining and perforate the sigmoid colon of which the outcome will be stomach disorders. I. Introduction and it is also observed in anorexia nervosa (Woywodt & Kiss, 2002). In Ghana, because the practice is geos- Deliberately eating earthy materials such as clay are patially distributed across the country, different names known globally as geophagy (Abrahams, 2003, 2013; have been given to the processed geophagic materials Al-Rmalli et al., 2010; Woywodt & Kiss, 2002; Ziegler, ready for ingestion. It is known as Ayilo (Ga), Agatawe 1997). The practice is a centuries-old practice that is (Ewes), Hyire (Akan) and several other names in other common worldwide but very much common in the dialects. Though the geophagic materials have differ - developing world. There are people who frowned ent names, the source materials are the weathered upon the practice but have on their part failed to products from the underlying bedrocks. The weath- justify their reasons scientifically. Despite the ill feel- ered rocks used as geophagic materials may contain ings from that school of thought, the geophagists have essential and harmful elements that may impact on seen the results of the practice to play a role of provid- health if the dose ratio for good health is exceeded ing some nutritional inputs in human development, (Arhin & Zango, 2017). The source materials may addressing some psychological and cultural goals, contain harmful elements such as aluminium, arsenic, while to others it is for medical guarantees (Danford mercury, lead, thallium, boron, and nickel etc. which et al., 1982). Meanwhile, others also crave to ingest the can be potentially harmful to humans (Arhin & geophagic materials just to satisfy spiritual, religious, Zango, 2017; Kariuki et al., 2016; Sarpong, 2015). In ritual, or social resolutions, whilst others eat it for the addition, many scientists have warned against the taste of it (Geissler et al., 1998; Hunter, 1993; Vermeer consumption of some geophagic materials by virtue & Ferrell, 1985). There is an interesting belief that the of their state as a pregnant woman or lactating mother ingested geophagic materials act as detoxifiers and this or as ordinary persons, since there are diverse health has been demonstrated by the practitioners in Ghana implications associated with its consumption (Steiner- by smearing their newborn babies with it (Mensah Asiedu et al., 2016). et al., 2010). There is no doubt that geophagia is beneficial but it Geophagia is prevalent in Ghana because most may also be harmful as the source of the geophagic pregnant women eat clay as an appetite suppressant material has a link to the underlying weathered rocks. CONTACT Rasheed Mohammed Abdul firstname.lastname@example.org Department of Geology, Pan African University Institute of Life and Earth Sciences (Including Health and Agriculture) (PAULESI), University of Ibadan, Ibadan, Nigeria © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of the International Water, Air & Soil Conservation Society(INWASCON). This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 R. M. ABDUL ET AL. Whatever the possible benefits are, there must be between 1700 mm and 1850 mm every year. The a way to balance the benefit with the bane because major season rainfall starts from mid-March to July, there exists the risk of ingesting the eggs of parasitic with the minor season occurring in September to mid- worms as well as exposure to toxic metal ions in the November. The annual temperature is fairly uniform, process. As noted by Arhin et al. (2016), the essential it averages 27°C during the rainy seasons and peaks at elements and the toxic elements coexist in the geopha- 31°C in March during the dry season. The mean gic materials. The oral ingestions of these materials do relative humidity is between 87 and 91% with the not separate the essential elements from the non- lowest relative humidity occurring usually in essential elements. However, the positive or negative February to April. During this period, the humidity effects of geophagia depend on the physicochemical, ranges between 83–87% in the morning and 48–67% chemical, biological and mineralogical properties of in the afternoon. Geologically the area is underlain by the materials ingested (Hooda, 2003; Mahaney et al., metasedimentary rocks comprising phyllites, grey- 1993; Wilson, 2003). Therefore, to make geophagy wackes, schists, with intrusions of basin granitoids more attractive and safe, studies that identify elemen- and gneisses (Figure 2). tal distributions and concentrations in the geophagic materials are relevant. More so, the knowledge of the III. Materials and methods mineralogy of the geophagic materials may give a hint on the possible health consequence if the material was The materials employed in the study include samples wrongly sourced. On the account of these, this study collected in the field, those collected at the field camps seeks to examine the mineralogical makeup and geo- and those purchased at the market from the geophagic chemical contents of geophagic materials at Mfensi- materials vendors. In all, twenty (20) geophagic mate- Adankwame community in the Ashanti Region of rials were collected in the field, at the field camps and Ghana. in the markets. Four (4) in situ samples were collected from dugout pits in the weathered clay zones in the regolith profile limit. The geophagic materials were II. Location, geology and physiographic randomly scooped within the saprolithic clay zone setting of study area until a weight of 1 kg was obtained. The scooping of The study was carried out at Mfensi-Adankwame, the samples was done at different points in the clay a town in the Atwima Nwabiagya Municipality in zones in the pits. Information such as type of the Ashanti Region of Ghana. It is about 22 km from underlying geology and characteristics of the overlying Kumasi, the capital of the Ashanti Region (Figure 1). saprolite and the plasticity of the geophagic materials The area is characterized by undulating topography sampled were recorded. Samples were taken from four with an average topographic height of about 77 m active pits where the locals were working in. Three (3) above sea level. The vegetation is semi-equatorial, samples each that add up to a total of 12 samples were marked by double maxima of rainfall that range collected from the bank materials excavated from the Figure 1. Location of the study area within the Atwima Nwabiagya Municipal. GEOLOGY, ECOLOGY, AND LANDSCAPES 3 Figure 2. Generalized Geological map of Ghana (Petersson et al., 2018). pits. Four (4) additional samples were also taken from materials using Ultra Trace Aqua Regia ICP-MS ana- already baked and ready to ingest molded clays from lytical procedure were used. X-ray fluorescence (XRF) vendors in Kumasi Central Market. Four quality analytical technique was used to determine the major assurance and quality control (QAQC) samples were oxides in the geophagic materials. The mineralogy of added to the field samples and the samples bought the geophagic materials were identified using the from the market. The quality assurance samples were X-ray diffraction technique that employs Qualitative duplicate pair of samples taken from the four already Analysis for complete mineralogy (coded XRDQual by baked and ready to ingest molded clays from vendors ALS). The samples were prepared using a back loading in Kumasi Central Market. The intent of these dupli- preparation method. Using this preparation method, cate samples was to assess the precision of the analy- the analysis was performed with a Malvern Panalytical tical quality of data. AERIS diffractometer with PIXcel detector and fixed The 20 total samples excluding the QA/QC samples silts with Fe filtered Co-Kα radiation. The mineral were processed first by sun drying for about 24 hours phases were identified using X’Pert Highscore Plus after which they were reduced by sieving to <125 μm software. The relative phase amounts (in weight size fraction. The sieved samples were then labeled and per cent) were also estimated using the Rietveld made ready for chemical and mineralogical analysis at method. ALS Geochemical laboratory in Kumasi. The sample The inductively coupled plasma (ICP) technique weight 100 g portion of all the samples were sent to the employed ALS-Chemex sample analysis protocol ME- laboratory for ICP-MS, XRF and XRD qualitative MS41 that uses both atomic emission spectrometry analyses. (ICP-AES) and mass spectrometry (ICP-MS) techni- ques. The combined methods used in this analytical protocol consist of near-total and partial extraction A. Method descriptions of the analytical methods. The near-total technique uses ICP-AES techniques method and characterizes the base metals such as Ag, Mineral identification studies using X-ray diffraction Cd, Co, Cu, Mo, Ni, Pb, Sc and Zn whereas elements analysis (Qualitative analysis for complete mineral- most appropriate for aqua Regia leach like As, Bi, Hg, ogy), and elemental composition of the geophagic Sb, Se, and Te were characterized in the samples by the 4 R. M. ABDUL ET AL. ICP-MS method. (Unpublished ALS-Group analytical C. Data analysis protocols: Galway-Ireland; www.alsglobal.com). The The elements obtained from the geochemical analysis data reported from aqua Regia leach represent only were categorized into Macro elements and Micro ele- the leachable portion of the particular analyte. This ments. The micro elements constitute both the essen- implies that recovery percentages for many analytes tial trace elements and toxic trace elements. This from more resistive major elements can be very low. In classification of the elements was based on the WHO this method, samples were digested with aqua Regia in Classification of Elements in 1973 and Frieden’s a graphite heating block and left to cool. The resulting Categorical Classification of Elements in 1974. solution was diluted with deionized water and subse- The concentrations of these elements were com- quently subjected to ICP-AES analysis. Results of the pared to the United State Geological Survey (USGS) initial analysis were reviewed for high concentrations average concentrations of elements in soils, and aver- of bismuth (Bi), mercury (Hg), molybdenum (Mo), age concentrations of elements in the Upper silver (Ag) and tungsten (W). ICP-MS analysis then Continental Crust (UCC) to determine enrichment commences for the remaining suite of elements. or depletion levels of the elements in the analyzed samples. The micro elements in the samples were compared with some known established toxic ele- B. pH and electrical conductivity (EC) ments also to assess the health risk of practitioners measurements on samples (United State Environmental Protection Agency [USEPA], 2002). The approach helped in completing 10 grams each of 8 in situ geophagic materials were the Health Risk Index (HRI) on ingestion of geophagic dissolved in 50 millilitres (mls) of distilled water in materials. The health risk index that depended on the labelled plastic test tubes. The test tube was covered Probable Daily Intake (PDI) of the geophagic materi- with a lid and the solution was placed on a sample als by the geophagic practitioners is the product of the vortex for rigorous mixing of the solution at maximum elemental concentrations (Conc ) of the max a speed of 2000 revolution per minute (rpm) for analyzed trace element and the mean daily consump- 60 seconds. The mixture was allowed to settle for tion (MDC) of the geophagic materials, expressed the milky part of the solution to be suspended at mathematically as: the top. JENWAY 350 pH meter was used for the pH measurement. Prior to performing sample mea- PDI ¼ Conc x MDC max surements, a 1 or 2-point calibration using mercury Meanwhile, from Arhin and Zango (2017), the free buffer solution(s) with pH of (4 ± 0.01) for mean daily consumption of geophagic materials by acidic, pH (7 ± 0.01) for neutral and pH the geophagic practitioners in Ghana is 70 g; and to (10 ± 0.01) for alkaline, all at room temperature simplify the computation, the body weight (BW) of were performed. The solution was then filtered the geophagic practitioners was assumed to be 60 kg. using Whatman filter paper into another test tube. Again, the Provisional Maximum Tolerable Daily The pH meter probe was gently immersed in the Intake (PMTDI), a requirement for the computation filtered solution and left for about 5 minutes for of the Health Risk Index (HRI) was obtained from the readings to stabilize before a reading was taken reports generated by Expert Committees of World from the LCD screen of the pH meter. To avoid Health Organization (WHO) and Food and cross contamination, the probe was immersed in Agriculture Organization (FAO). The Health Risk water between each successive test. Index (HRI) was then calculated from the ratio of The electrical conductivity of the samples was the Probable Daily Intake (PDI) to the Provisional measured using the Hanna Instrument. Before tak- Maximum Tolerable Daily Intake (PMTDI) of trace ing measurements, the meter was calibrated by elements as: immersing the probe in a calibration solution of known conductivity. The filtered solutions for each PDI HRI ¼ of the samples were poured in labelled plastic bea- PMTDI kers. Plastic beakers were used to minimize electro- The interpretation of Health Risk Assessment magnetic interferences. The EC measurements on according to USEPA (2002) is given as HRI < 1 as the samples were taken by submerging the probe in safe for human health whereas HRI > 1 as unsafe for the filtered solutions. The measurement was taken human health. when the stability symbol on the top left of the LCD disappears. The EC value in microsiemens per centimeter (µS/cm) automatically compensated IV. Results and discussions for temperature was shown on the primary LCD while the secondary LCD showed the temperature Shown in Figure 3 are the minerals identified in the of the sample (in °C). geophagic samples analyzed using the XRD GEOLOGY, ECOLOGY, AND LANDSCAPES 5 Figure 3. Abundance of mineral contents in the geophagic materials. Qualitative Analytical technique. The minerals identi- obtained from the laboratory was considered accepta- fied are Quartz, Muscovite and Kaolinite. As presented ble. Hence, the selected results of the chemical analysis in Figure 3, quartz appeared to be the most dominant performed on the field in situ samples, the bank sam- mineral in all the in situ samples and has an inverse ples at the field camp and samples purchased at the relationship with kaolinite in terms of mineral con- market are presented in Table 1. The measured ele- centrations in all analyzed samples (Figure 4). ments concentration levels differed from sample to Figure 5 shows the analytical quality of the data sample with many of the samples registering measured received from the laboratory using Cu concentration results below detection limits of the analytical instru- levels in the duplicate pairs of samples. As seen in ment. In this study, discussions were made on ele- Figure 5, the differences in Cu concentrations between ments that had Public Health consequence if not the duplicate pairs are marginal suggesting analytical monitored. Some of these elements have been estab- result may be reproducible and will have good preci- lished as essential for good health and others toxic if sion. With this precision in analysis, the results exposure exceeds certain tolerable limits. The ele- ments are As, Cd, Cr, Cu, Hg, Mn, Mo, P, Pb, Th, Tl, Zn, Fe, K, Mg and Ca (Table 1). Apart from the toxic elements known to have carcinogenic effects, there are some essential elements that collectively per- form five general physiological roles such as water and electrolyte balancing, metabolic catalysis, oxygen binding and transport as well as hormonal effects in the human body. But the achievements of the physio- logical roles only happen when there is an existence of right dose of the elements in the human system. The elements in Table 1 are classified into macro elements (i.e., Na, Mg, P, K, Ca), micro elements (Co, Cr, Cu, Fe, Mn, Mo, Se, Zn) and toxic trace elements (Cd, Hg, As, Pb). Table 2 shows the summary statistics and crustal averages with enrichment/depletion status. From Table 2, the mean concentration of Na is 0.0335 wt% which is below the background value of 1.2 wt%. The average concentration of Mg in the Figure 4. Scatter plot diagram of quartz versus kaolinite in the studied geophagic samples. samples is also 0.0330 wt% which is below the USGS 6 R. M. ABDUL ET AL. Analycal Precision using Cu Values in Samples Orig. (Cu ppm) Dup (Cu ppm) SC001 SC002 SC003 SC004 Duplicate Pairs of Samples Figure 5. Analytical quality of results using Cu levels in the duplicate pairs of samples for precision studies. Table 1. Elements and their concentrations in the geophagic samples. As Ca Cd Cr Cu Fe Hg Mn Mo P Pb Th Tl Zn K Mg Se SAMPLE ID ppm wt% ppm ppm ppm wt% ppm ppm ppm ppm ppm ppm ppm ppm wt% wt% ppm LOD 0.1 0.01 0.01 1 0.2 0.01 0.01 5 0.05 10 0.2 0.2 0.02 2 0.01 0.01 0.2 MF/AD-01FG 0.4 0.02 - 23 3.8 0.22 0.01 16 0.05 20 2.7 2.5 0.02 5 0.06 0.01 - MF/AD-02FG 0.5 0.01 0.01 14 3.7 0.24 - 17 - 20 2.2 3.1 0.02 11 0.04 0.02 - MF/AD-03FG 0.4 0.02 - 20 5.4 0.23 - 17 0.05 40 4.5 3.4 0.03 3 0.14 0.02 - MF/AD-04FG 0.2 0.02 - 25 12.5 0.34 - 24 - 50 5.7 3.6 0.03 10 0.12 0.03 0.3 MF/AD-01PG1 0.9 0.02 0.01 31 17.2 0.47 - 38 0.05 80 7.6 4.9 0.06 8 0.23 0.04 - MF/AD-02PG1 1 0.02 - 12 15.4 0.26 - 22 - 90 6.9 5.1 0.02 5 0.06 0.03 - MF/AD-03PG1 1.2 0.02 0.01 22 17.3 0.44 - 39 0.05 90 7.6 5.1 0.04 5 0.14 0.03 0.2 MF/AD-01PG2 1.2 0.03 0.01 20 9.8 0.36 0.01 36 0.05 70 4.5 3.5 0.03 4 0.16 0.03 0.2 MF/AD-02PG2 1.1 0.03 0.01 21 9.8 0.44 0.01 42 0.06 70 4.5 3.5 0.04 6 0.15 0.03 - MF/AD-03PG2 1 0.03 - 21 9.3 0.41 - 39 0.05 70 4.4 3.3 0.04 6 0.17 0.03 - MF/AD-01PG3 1.1 0.02 0.01 19 11.8 0.44 - 47 0.05 60 4.5 3.3 0.03 7 0.14 0.04 0.2 MF/AD-02PG3 1.1 0.02 - 20 12.2 0.4 - 44 - 60 4.7 3.3 0.04 6 0.15 0.04 - MF/AD-03PG3 1.2 0.02 0.01 20 11.3 0.45 0.01 47 0.06 60 4.5 3.3 0.03 6 0.13 0.04 0.2 MF/AD-01PG4 1.3 0.03 0.01 22 16.4 0.52 - 53 0.05 60 5.1 3.2 0.04 9 0.16 0.05 - MF/AD-02PG4 1.3 0.03 - 23 15.9 0.56 - 58 0.06 70 4.8 3.2 0.03 8 0.14 0.05 - MF/AD-03PG4 1.4 0.03 - 22 15.6 0.52 - 52 0.05 70 4.9 3.2 0.04 10 0.15 0.05 0.3 MF/AD-01 MG 0.5 0.02 - 25 11.4 0.42 - 29 0.06 50 5.3 3.4 0.04 3 0.15 0.03 - MF/AD-02 MG 0.7 0.02 - 24 11.6 0.36 - 22 - 50 5.5 3.5 0.03 5 0.14 0.03 - MF/AD-03 MG 0.4 0.02 - 24 11.6 0.38 - 25 0.05 50 5.4 3.5 0.03 4 0.13 0.03 0.2 MF/AD-04 MG 0.5 0.02 - 22 11.3 0.36 - 20 - 50 5.4 3.3 0.03 10 0.13 0.03 - Values below limit of detection have been replaced by dash (-) value of 0.9 wt%. Conversely, all the samples analyzed away from the mean concentrations (Table 2). The had P concentrations above limit of detection but their departure of the micro elements from their back- mean concentration lower than the background con- ground values were as follows: mean Co concentration centration. The mean concentration of P is 59 ppm in the samples was 1.00 ppm compared to the back- whilst the background concentration is 430 ppm. ground concentration of 9.10 ppm; the mean concen- K and Ca concentrations in the samples were both tration of Cr, Cu and Fe were 21.5 ppm, 11.7 ppm and below the background concentrations, recording 0.391 ppm compared to their background concentra- 0.135 wt% and 0.0225 wt% respectively as compared tions of 54.0 ppm, 25.0 ppm and 2.60 ppm, respec- to USGS average concentrations of elements in soils of tively; Mn and Se mean concentrations in the samples 1.50 wt% for K and Ca, 2.40 wt%. All the macro were lower than their respective background concen- elements had concentrations lower than their respec- trations although Se was detected in only seven out of tive background concentrations (Figure 6) with con- the twenty samples analyzed (Table 1). The mean centration values ranging from (0.01–0.03) wt% for concentration of Mn in the samples was 34.4 ppm Ca; (0.01–0.05) wt% for Mg; (0.01–0.04) wt% for Na; and that of Se was 0.229 ppm. Mo mean concentration (0.04–0.23) wt% for K; and (20–90) ppm for P. Despite though absent in six of the samples was 0.0529 ppm that, the standard deviations of the elements were very and the background concentration 0.970 ppm. Zn low except for P. This signifies that the elemental showed depletion in concentration in all the samples. compositions in the individual samples are not far The mean and background concentration of Zn was Cu ppm GEOLOGY, ECOLOGY, AND LANDSCAPES 7 Table 2. Summary statistics of Results showing Enrichment/Depletion status of the elements as compared to the Crustal Averages of the elements in soils. Mean Difference Percentage Elements Min Max Median (Cn) SD Bn (Cn-Bn) Difference Status Macro elements Ca 0.0100 0.0300 0.0200 0.0225 0.00550 2.40 −2.38 −99.1 Depleted Mg 0.0100 0.0500 0.0300 0.0330 0.0103 0.900 −0.867 −96.3 Depleted Na 0.0100 0.0400 0.0400 0.0335 0.00933 1.20 −1.17 −97.2 Depleted K 0.0400 0.230 0.140 0.135 0.0417 1.50 −1.37 −91.0 Depleted P 20.0 90.0 60.0 59.0 18.9 430 −371 −86.3 Depleted Micro elements Fe 0.220 0.560 0.405 0.391 0.0975 2.60 −2.21 −85.0 Depleted Co 0.500 1.30 1.20 1.00 0.288 9.10 −8.10 −89.0 Depleted Cr 12.0 31.0 22.0 21.5 3.94 54.0 −32.5 −60.2 Depleted Cu 3.70 17.3 11.6 11.7 4.04 25.0 −13.3 −53.2 Depleted Mn 16.0 58.0 37.0 34.4 13.4 550 −516 −93.8 Depleted Mo 0.0500 0.0600 0.0500 0.0529 0.0252 0.970 −0.917 −94.6 Depleted Zn 3.00 11.0 6.00 6.55 2.46 60.0 −53.5 −89.1 Depleted Se 0.200 0.300 0.200 0.229 0.115 1.30 −1.07 −82.4 Depleted Toxic trace elements As 0.200 1.40 1.00 0.870 0.379 7.20 −6.33 −87.9 Depleted Hg 0.0100 0.0100 0.0100 0.0100 0.00410 0.0900 −0.0800 −88.9 Depleted Pb 2.20 7.60 4.85 5.04 1.32 19.0 −14.0 −73.5 Depleted Cd 0.0100 0.0100 0.0100 0.0100 0.00503 0.0900 −0.0800 −88.9 Depleted Min = Minimum; Max = Maximum; SD = Standard Deviation; Bn = Background value Figure 6. Comparison of measured mean ofmacro elements with their crustal averages. 6.55 ppm and 60 ppm, respectively (Table 2). in all the samples, and recorded a mean concentration Similarly, the mean concentrations of the micro ele- of 5.04 ppm. The analysis showed the elements As, Cd, ments in all the samples collected compared to the Hg and Pb were depleted in the samples when com- crustal averages also showed depletion in all elements pared to their background concentrations (Figure 8). (Figure 7). The implications are that the practitioners This has a positive outcome as the human bodies do will lose out because all the essential elements are not need these elements for their physiological roles. below detection and showed depletion if the consump- From the pH measurements, all the samples tion of the geophagic materials is for medicinal recorded values ranging from 7.43 to 8.36 depicting purposes. alkaline environment (Table 4). According to The concentrations of some known toxic trace ele- Andrews-Jones (1968), in a neutral to alkaline envir- ments in the samples were observed to have As values onment, the elements Cr, Th, Zn, Cu, Co, Hg are very to range from 0.2 to 1.4 ppm with an average concen- low to immobile; P, K, Pb, Tl, Fe and Mn have low tration of 0.870 ppm. Cd concentrations in all the mobility; As and Cd have medium mobility; Ca, Na, samples were below limit of detection except eight of Mg have high mobility; whilst S, Mo, Se and have very them which recorded 0.01 ppm. Hg concentrations in high mobility. The depletion of macro elements (K majority of the samples were below detection except and P) in the geophagic materials could be due to for only four of the samples (Table 1). Pb was detected their low mobility in the alkaline environment. The 8 R. M. ABDUL ET AL. Figure 7. Comparison of measured mean of micro elements with their crustal averages. Figure 8. Comparison of measured mean of toxic trace elements with their crustal averages. mobility of the micro elements Fe and Mn (low mobi- of essential chemical constituents in the geophagic lity), Co, Cr, Cu, Zn (very low to immobile) in the materials (Depetris, 1998). neutral to alkaline environment depicts their low con- Soil electrical conductivity (EC) is a measure of the centration levels in the geophagic materials. Similarly, amount of salts in soil (salinity of soil). It is important the toxic trace elements Pb and Hg have low and very indicator of soil health. According to Smith and Doran low to immobile mobilities, respectively which (1997), soils having EC of (0–2.0) dS/m are non-saline, accounts for their low concentrations in the geophagic (2.1–4.0) dS/m are slightly saline, (4.1–8.0) dS/m are materials. Though the macro elements (Ca, Na, Mg), moderately saline, (8.1–16.0) dS/m are strongly saline micro elements (Mo, Se) and toxic trace elements (As, and soils having EC greater than 16.0 dS/m are very Cd) have high, very high and medium mobilities, saline. From Table 4, EC values of the geophagic respectively, but showed depleted concentrations in samples falls below 2.0 dS/m. This shows that the the geophagic materials. This could be attributed to geophagic materials are non-saline. Also, soils domi- the high chemical index of alteration (CIA) values of nated by clay minerals that have a low cation- the geophagic materials (Table 6). This is because high exchange capacity (CEC), such as kaolinite CIA values could be indicative of low concentrations (Figure 3), have lower EC (as shown in Table 4) GEOLOGY, ECOLOGY, AND LANDSCAPES 9 (Unpublished United States Department of Table 3. Daily trace element intake from 70 g geophagic materials collected and calculated health risk index in the Agriculture (USDA) Soil Electrical Conductivity–Soil study area. Quality Kit Guide). In this study, the electrical con- PDI WHO/ ductivity values of all the samples are far lower than Cmax (µg/ FAO PMTDI for the standard global conductivity values (Table 5) in (mg/ kg/ PMTDI 60 kg BW Element kg) day) for 1 kg (µg/kg/day) HRI Remarks similar materials. With the macro elements, Ca has the As 1.4 98 3.0 180 0.544 Safe highest EC value, followed by Mg, to Na, K, and P the Pb 7.6 532 3.0 180 2.96 Not Safe least. The micro elements have the following order of Hg 0.01 0.7 0.6 36 0.0194 Safe Cd 0.01 0.7 0.3 18 0.0389 Safe decreasing EC values as Cu > Mo > (Co, Zn) > Fe > Cr Cr 31 2170 35 2100 1.03 Not Safe > Mn, whilst Se has no EC value. Cd has the highest Co 1.3 91 20 1200 0.0758 Safe Ni 6.7 469 70 4200 0.112 Safe EC value for the toxic trace elements followed by Pb, Cu 17.3 1211 900 54000 0.0224 Safe to As, and then Hg. Low EC values recorded for all the Mo 0.06 4.2 450 27000 0.000156 Safe samples means that there is not enough water for the elements to be released from the parent material and Table 4. pH and Electrical Conductivity (EC) measurements on this accounted for the low concentration of all the the geophagic materials. analyzed elements in the geophagic material. Sample ID Weight (g) pH EC (µS/cm) EC (dS/m) MF/AD-01PT1 10 8.10 39 0.039 MF/AD-02PT1 10 7.99 20 0.020 A. The health risk due to elements in the studied MF/AD-01PT2 10 7.77 19 0.019 geophagic materials MF/AD-02PT2 10 7.60 28 0.028 MF/AD-01PT3 10 7.43 90 0.090 MF/AD-02PT3 10 8.32 155 0.155 The geophagic samples contain significant amounts of MF/AD-01PT4 10 8.31 74 0.074 kaolinite and quartz. Recounting from Kikouama et al. MF/AD-02PT4 10 8.36 29 0.029 (2009) and Alexander (1977), clays with high kaolinite may provide medicinal benefit. This means the inges- PDI of 2170 µg/kg/day compared to the tolerable daily tion of clay balls from the study area will have positive intake of 2100 µg/kg/day was calculated for Cr. For Pb, impact on the health of geophagic individuals. PDI of 532 µg/kg/day was calculated as greater than On the contrary, the high amounts of quartz in the the permitted maximum tolerable daily intake of samples may erode the benefits provided by kaolinite. 180 µg/kg/day (Table 3). Chromium and lead in the The reason is the main component of the human samples exceeded the limit with which they can be dental enamel is made up of hydroxyapatite [Ca declared safe for consumption, i.e., HRI for Cr and (PO ) OH] which has a hardness of 5 on the Mohs 4 3 Pb = > 1. Though, the measured Cr is total Cr and it scale of hardness (Ekosse & Ngole, 2012). The ingested could be either trivalent or hexavalent Cr. These two geophagic material containing predominantly quartz forms of Cr are the dominant oxidation forms as has a higher degree of hardness (7). Ingesting the 3+ noted by Bartlett and James (1988). Whereas Cr is geophagic material may accidentally damage dental 6+ considered as essential microelement, Cr is consid- enamel during mastication (Diko & Ekosse, 2014). In ered to be highly toxic to humans (Megharaj et al., addition, the quartz particles in the geophagic materi- als can also erode the gastro-intestinal lining of the geophagic practitioners which could possibly perfo- Table 5. Standard Global Electrical Conductivity (EC) values of rate the sigmoid colon (Ekosse et al., 2017). The con- elements. sequence will be stomach disorders. The cultural and Element EC (dS/m) traditional systems seek to build strong and healthy Macro elements societies and will not want the inhabitants to ingest Ca 2.9 × 10 Mg 2.3 × 10 geophagic materials to make them sick neither will Na 2.1 × 10 religious leaders intend to superintend unhealthy 8 K 1.4 × 10 P 1.0 × 10 community and therefore will not want their consti- Micro elements tuents to practice something that will make them Cu 5.9 × 10 unwell. The perceptions and motivations of geopha- 8 Mo 2.0 × 10 Co 1.7 × 10 gists are not backed by science and data and therefore Zn 1.7 × 10 require breakeven point where there is a balance 8 Fe 1.0 × 10 Cr 7.9 × 10 between benefits and banes. Mn 6.2 × 10 Additional information from the Health Risk Se N/A Assessment based on the health risk index on the Toxic trace elements Cd 1.4 × 10 samples revealed that ingesting 70 g daily of these Pb 4.8 × 10 geophagic materials is unsafe. This is because the As 3.3 × 10 probable daily intake of Cr and Pb are at levels higher Hg 1.0 × 10 than the permissible maximum tolerable daily intake. *Arranged in decreasing order of EC values (from highest EC value to least) 10 R. M. ABDUL ET AL. Table 6. Major oxides concentrations and chemical index of conditions (be it acidic, alkaline, neutral, oxidizing or Alteration (CIA) values of the geophagic materials. reducing environments) if available in the underlying Sample ID/ MF/AD- MF/AD- MF/AD- MF/AD- rocks will be released and be mobilized in the soils. All Major oxides 01FG 02FG 03FG 04FG the micro elements analyzed in the geophagic materi- Al O 16.79 18.26 16.65 17.29 2 3 als in this study behaved like the macro elements BaO 0.07 0.08 0.12 0.10 CaO 0.08 - - - K and P, of which all of them have low mobility Cr O - - - - 2 3 because of the low alkaline environment. The low Fe O 1.36 0.51 6.25 5.36 2 3 K O 1.65 1.94 3.71 3.36 concentrations of the micro elements recorded in the MgO 0.34 0.21 1.13 1.00 samples will have limited spread and their uptake by MnO - - - - Na O 0.12 0.08 - - 2 plants may be localized. The electrical conductivity NiO - - - - values of all the samples were far lower than the P O - - 0.13 0.16 2 5 SiO 71.24 72.29 65.26 65.86 standard global conductivity values of the elements SO - - 0.55 0.24 in similar materials. This deprived the release of the TiO 0.73 0.82 1.09 1.01 elements from the source material which led to the low V O - - - - 2 5 LOI 5.32 5.34 5.31 5.52 concentration values recorded for all the analyzed Sum 97.70 99.53 100.20 99.90 elements in the geophagic materials. More so, the CIA 90.08 90.04 81.78 83.73 concentrations of the essential elements (macro ele- ments and micro elements at certain concentration 6+ level) in the samples were low, which could be attrib- 2003). Cr toxicity in humans is accompanied with uted to high chemical index of alteration (CIA) values damaging of blood cells, livers, nervous systems, and by virtue of the area lying in the rainforest region. The kidneys, causing stunted growth in babies (Mackenzie known toxic elements were deficient in the samples et al., 1958; Waldron, 1980). Pb is considered as poten- analyzed. Despite that, some health risks were identi- tially harmful element which is generally toxic to fied to be associated with Pb and Cr as the calculated humans. Pb has negative effects on kidneys, nervous Health Risk Index values were greater than one (> 1) system and heart, and leads to reduced fertility. The signifying a health threat to the geophagic department of Health and Human Services (DHHS), practitioners. Environmental Protection Agency (EPA) and Additionally, the study found the mineral constitu- International Agency for Research on Cancer (IARC) ents of the geophagic materials to contain quartz, kao- have determined that Pb is probably cancer-causing in linite and muscovite, with quartz as the dominant humans (U.S. Department of Health and Human mineral. Excessive amount of quartz and toxic trace Services, 2007). Hence the presence of Cr and Pb in elements in the geophagic materials could pose detri- the geophagic materials should make the practice be mental health threats to the practitioners as against considered as detrimental to human health and should kaolinite that provides medicinal benefit to the geopha- not be encouraged just because the practitioners crave gic individuals. The hardness of quartz can damage for it. dental enamel during mastication and could erode the gastro-intestinal lining of the geophagic practitioners V. Conclusion leading to a perforated sigmoid colon of which the outcome will lead to stomach disorders. The authors The geophagic materials from Mfensi-Adankwame conclude that for geophagy to be attractive, the knowl- contain macro elements such as Na, Mg, P, K and edge of the mineralogy and geochemistry of geophagic Ca; micro elements including Co, Cr, Cu, Fe, Mn, materials must be known in order to strike the balance Ni, Se, V and Zn; and known toxic elements such as between the essential and harmful elements as well as As, Cd and Pb. The pH values measured for all the adopting a method to reduce the amount of quartz samples revealed that the soils in the oxidized envir- content in order to make it safe for ingestion. More onment at the study area is alkaline and ranges from so, because of the variability of geochemistry of geolo- 7.43 to 8.36. This means that macro elements such as gic materials across the landscape, the authors recom- K and P that have low mobility in an alkaline environ- mend the need to identify the provenance of the ment will be patchily distributed in the source materi- geologic makeup of the geophagic materials, which als. This suggests that not all geophagic materials dug consequently may relate to different rock types. This and processed for ingestion will contain these macro would be useful tool to suggest the likely elements elements K and P useful for some physiological roles contained in the geophagic materials consumed by in the geophagic practitioners. Conversely, Ca, Na and the practitioners. Knowledge of this information Mg that have high mobility under all environmental GEOLOGY, ECOLOGY, AND LANDSCAPES 11 could provide a guide to where geophagic materials Diko, M. L., & Ekosse, G. E. (2014). Soil ingestion and associated health implications: A physicochemical and could be sourced to avoid spreading preventable public mineralogical appraisal of geophagic soils from Moko, health diseases from harmful elements exposures. Cameroon. Studies on Ethno-medicine, 8(1), 83–88. https://doi.org/10.1080/09735070.2014.11886476 Ekosse, G. E., & Ngole, V. M. (2012). Mineralogy, geochem- Acknowledgments istry and provenance of geophagic soils from Swaziland. Applied Clay Science, 57, 25–31. https://doi.org/10.1016/j. The authors would like to acknowledge with much appre- clay.2011.12.003 ciation to African Union Commission through Pan African Ekosse, G. I. E., Ngole-Jeme, V. M., & Diko, M. L. University Institute for Life and Earth Sciences (including (2017). Environmental geochemistry of geophagic Health and Agriculture) (PAULESI) for funding this materials from Free State Province in South Africa. research. Open Geosciences, 9(1), 114–125. https://doi.org/10. 1515/geo-2017-0009 Geissler, P. W., Shulman, C. E., Prince, R. J., Disclosure statement Mutemi, W., Mnazi, C., Friis, H., & Lowe, B. (1998). Geophagy, iron status and anaemia among pregnant No potential conflict of interest was reported by the women on the coast of Kenya. Transactions of the author(s). Royal Society of Tropical Medicine and Hygiene, 92 (5), 549–553. https://doi.org/10.1016/S0035-9203(98) 90910-5 ORCID Hooda, P. S. (2003). Soil ingestion affects the potential bioavailability of Cu, Mn, and Zn. In Proceedings of the Rasheed Mohammed Abdul http://orcid.org/0000-0002- 7th International Conference on the Biogeochemistry of 3875-2801 Trace Elements (pp. 8–11). Uppsala, Sweden. Emmanuel Arhin http://orcid.org/0000-0002-1724-8307 Hunter, J. M. (1993). Macroterme geophagy and pregnancy clays in southern Africa. 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Geology Ecology and Landscapes – Taylor & Francis
Published: Oct 2, 2023
Keywords: Earth products; Aqua Regia; trace element; stomach disorder; sigmoid colon
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