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Elemental minerals and microbial compositions as well as knowledge and perceptions regarding kaolin (clay) consumption by pregnant women in the Ho municipality of Ghana

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Overview

This cross-sectional study from the University of Health and Allied Sciences, Ho, Ghana measured the elemental mineral content and microbial load of kaolin clay samples collected from the Anfoega mining site and local market channels in the Ho municipality, Volta Region. It also surveyed 217 pregnant women attending antenatal clinics to document geophagy prevalence, motivations, and perceptions of side effects. The clay was analyzed by atomic absorption spectrophotometry (AAS) for macro minerals (iron, copper, zinc, potassium, magnesium, sodium) and micro/toxic minerals (arsenic, manganese, lead, nickel). The key finding is that mean lead and arsenic concentrations in the clay were below the WHO/FAO PMTDI comparators used by the authors, while the clay harbored pathogenic microorganisms including Bacillus spp., Pseudomonas spp., Mucor spp., and Aspergillus spp.

Key numbers

Mineral concentrations in kaolin clay samples (Table 4 of source):

Macro minerals (mean concentration):

  • Iron (Fe): 1.38 +/- 1.5 mg/kg (WHO RDI: 18 mg)
  • Copper (Cu): 2.40 +/- 1.5 mg/kg (WHO RDI: 0.9 mg)
  • Zinc (Zn): 7.74 +/- 1.5 mg/kg (WHO RDI: 11 mg)
  • Potassium (K): 4.01 +/- 1.0 mg/kg (WHO RDI: 3100-3500 mg)
  • Magnesium (Mg): 13.24 +/- 2.2 mg/kg (WHO RDI: 280-350 mg)
  • Sodium (Na): 13.76 +/- 2.1 mg/kg (WHO RDI: 500-2400 mg)

Micro/toxic minerals (mean concentration):

  • Arsenic (As): 1.63 +/- 0.03 microg/kg (WHO/FAO PMTDI: 3.0 microg/kg BW/day; PMTDI for 60 kg person: 180 microg/day)
  • Manganese (Mn): 4.72 +/- 0.8 mg/kg (WHO/FAO PMTDI: 4.9 mg/kg; PMTDI for 60 kg: 294 mg/day)
  • Lead (Pb): 0.53 +/- 0.02 mg/kg (WHO/FAO PMTDI: 3.0 microg/kg BW/day; PMTDI for 60 kg: 180 microg/day)
  • Nickel (Ni): 1.85 +/- 0.3 mg/kg (WHO/FAO PMTDI: 5.0 microg/kg BW/day; PMTDI for 60 kg: 300 microg/day)

Note: arsenic units in Table 4 are stated as microg/kg, while Pb, Mn, and Ni are stated as mg/kg. This unit distinction is as reported in the original table; arsenic at 1.63 microg/kg (1.63 ppb) is a very low value. The authors state these concentrations are within permissible levels (WHO); however, they note that accumulated effects of these metals can lead to various complications in pregnancy.

Context from other Ghanaian studies cited in source:

  • Ref 37 (Tayie et al.): 0.0 mg/kg (nil) arsenic in clay samples from Accra, Ghana
  • Ref 38 (Nkansah et al.): arsenic 218-271 ppm from clay samples in different parts of Kumasi metropolis
  • Ref 39 (Doe et al.): arsenic range 2.7-22.74 microg/g in nine clay samples from Greater Accra and Kumasi (this deposit’s evidence.md verbatim excerpt quotes this as “2.7-22.74 µg/g”)
  • Lead in this study: 2.36 +/- 0.08 mg/kg (from discussion section, p. 6, comparing with Ref 38 which reported 549-622.92 microg/kg)
  • Arsenic levels from Ref 39 in nine Greater Accra and Kumasi samples: 2.7-22.74 microg/g

Microbial findings (Table 5 of source):

  • Anfoega mining site ore (Anf/Ms/ORE): Pseudomonas spp. and Bacillus spp.; TPC 9.5x10^2-9.8x10^2 CFU/g on BA and PDA
  • Anfoega retail shop, not baked (Anf/RET/NB): Bacillus spp. and Mucor spp.; TPC 2.0x10^1 CFU/g
  • Ho market, baked (Ho/mkt/B): Bacillus spp., Pseudomonas spp., Aspergillus spp.; TPC 5.0x10^1 CFU/g on PDA
  • Ho market, not baked (Ho/Mkt/NB): Pseudomonas spp. and Bacillus spp.; TPC 4.0x10^1-5.0x10^1 CFU/g
  • No helminths, protozoans, cysts or ova-like structures identified by parasitological analysis

Geophagy prevalence (survey, n=217 pregnant women):

  • Prevalence of geophagy in this sample: 48.4% (n=217); 177 (81.6%) had consumed clay before
  • 132 (74.6%) consumed clay once daily; 25 (14.1%) twice
  • 117 (53.9%) had cravings to eat clay during pregnancy; 105 (89.7%) of the 117 ate clay during pregnancy
  • 108 (49.8%) heard about clay (ayilo) from peers; 101 (46.5%) from family
  • Primary reasons for consumption: smell (45.8%), craving (29.4%), nausea (29.9%), taste (24.9%), fun (29.9%), peer influence (11.3%), hunger (2.3%), health reason (3.4%)
  • 129 (59.4%) of pregnant women knew there were some side effects; 52 (24%) said there was no side effect; 20 (9.2%) did not know

Women’s perceptions of side effects:

  • 76 (58.9%) believed geophagy causes anemia
  • 60 (46.5%) believed it causes constipation
  • 46.5% reported constipation; 53.5% did not
  • 2 (1.6%) believed it caused menstrual cramps; 12.4% believed it caused infertility
  • 37 (28.7%) believed it caused abnormal baby skin color during delivery

Evidence Fitness

EF-3 (modeled or limited evidence). This study provides primary AAS measurements of mineral content in kaolin clay from a specific mining and market source in Ho municipality, Ghana. The analytical method (dry ashing, AAS) is described with sufficient detail. The sample set is small: four sample types (mining ore, retail unbaked, market baked, market unbaked). No CRM or recovery data are reported, and no LOD/LOQ is stated explicitly. No replicate statistics across sampling occasions are described; the mean values with standard deviations in Table 4 likely represent analytical replicates from a small number of samples rather than multiple independent sampling events. Comparison with WHO PMTDI is a crude risk screen: it uses total metal values without bioaccessibility adjustment, and the PMTDI for a 60 kg adult is not equivalent to intake from clay alone. The arsenic value (1.63 microg/kg) is notably low relative to other Ghanaian clay studies cited in the paper (Nkansah et al.: 218-271 mg/kg; Doe et al.: 2.7-22.74 microg/g), suggesting matrix heterogeneity or analytical difference. The prevalence survey data (n=217) are the most robust component of this paper.

Methods (brief)

Clay analysis: Dry ashing method at 550 degrees C for 8 hours in a muffle furnace. Platinum crucibles. Five millilitres of 65% nitric acid added after cooling. Dilution to 50 mL with 0.1 mol/L nitric acid. AAS reading using Buck Scientific 210VGP Flame AAS with appropriate cathode lamps: Cu (324.8 nm), Fe (248.3 nm), Mn (279.5 nm), Pb (217.0 nm), Zn (213.9 nm). Calibration curves from minimum three standards. Clay samples were ground to 0.1 mm mesh powder. Official method of Analysis 18th edition (AOAC) methods 935.14 and 992.24 (2005) referenced.

Microbial analysis: Blood Agar (BA), Sabouraud Dextrose Agar (SDA), and Potato Dextrose Agar (PDA) at 37 degrees C for 48 hours. TPC as CFU/g. Fungi enumerated by PDA and SDA with 0.1% peptone. Parasitological examination by formol-saline wet mount method.

Survey: Structured questionnaire, cross-sectional design. Convenient sampling of 217 pregnant women at Volta Regional Hospital and Ho Municipal Hospital. Face-to-face interviews. Data analyzed with EpiInfo 4.2 and IBM SPSS Statistics 25.

LOD/LOQ: Not stated. CRM: Not reported. Recovery: Not reported.

Implications

Certification: The measured concentrations in this study (lead 0.53 mg/kg, arsenic 1.63 microg/kg, nickel 1.85 mg/kg) are below the WHO PMTDI comparators used by the authors for a 60 kg adult consuming their reported quantities. However, this study does not report bioaccessible fractions, and other Ghanaian studies cited in this paper find arsenic concentrations several orders of magnitude higher in clay from the same region (Nkansah: 218-271 mg/kg; Doe: 2.7-22.74 microg/g). The inter-study variance is so large that no pooled typical-ppb value for Ghanaian geophagic clay can be computed from the available set without understanding sampling location, clay type, and analytical protocol differences.

Courses: The geophagy prevalence figure (48.4% of pregnant women in this sample) and the 89.7% continuation rate during pregnancy are strong quantitative anchors for understanding the scale of this exposure pathway among a specific population (pregnant women in Ho municipality, Volta Region, Ghana). The contamination profile across four distribution channels (mine ore, retail unbaked, market baked, market unbaked) illustrates how baking reduces microbial load but does not eliminate it.

App: The mean lead value (0.53 mg/kg = 530 ppb wet weight) and mean arsenic (1.63 microg/kg = 1.63 ppb) for this Ghanaian kaolin source, with n=4 sample types, insufficient for a contamination profile update. Cross-study comparison shows variance too high for a single-site update to be representative.

Microbiome: Aspergillus spp. isolated from Ho market baked clay; Mucor spp. from Anfoega retail unbaked; both are opportunistic pathogens. The presence of Bacillus spp. and Pseudomonas spp. across all sample types regardless of baking represents a persistent microbial exposure pathway associated with clay ingestion.

Provenance notes

Open access, CC BY license. Full text retrieved from PubMed Central (PMC6961938). SHA-256 verified against MANIFEST.csv for HMI-FILL-0002. No retraction flag. The Pan African Medical Journal is published in partnership with the African Field Epidemiology Network (AFENET). Ethical clearance from Research and Ethics Committee, University of Health and Allied Sciences, Ho, Ghana.

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