Keywords
kaolin
geophagy
bioaccessibility
trace metal elements
health risk
Kimbanseke
Kinshasa
How to Cite
Abstract
Introduction
In Kinshasa, kaolin consumption is a deeply rooted cultural practice, particularly among women. However, it represents a major exposure pathway for chemical contaminants, while the toxicological risks associated with trace metal elements (TMEs) remain poorly documented.
Purpose
This study evaluated health hazards associated with kaolin consumption. The overall objective was to assess health exposure risks among women in Kimbanseke to TMEs (lead, cadmium, and arsenic) resulting from geophagy. Specifically, the study aimed to (a) identify consumers and assess their level of exposure; (b) measure total concentrations of Pb, Cd, and As; (c) determine their in vitro bioaccessible fractions (gastric and intestinal phases) to calculate the Average Daily Dose (ADD), Hazard Quotient (HQ), and Hazard Index (HI); and (d) propose a decision-making tool.
Methods
A cross-sectional survey was conducted among 100 respondents in Kimbanseke. Physicochemical characterization was performed using X-ray fluorescence (XRF) to determine total metal concentrations. In vitro digestion simulation was conducted using a bioaccessibility model mimicking the gastric phase (pH 1.5) and intestinal phase (pH 7.0).
Results
XRF analyses revealed alarming total concentrations at Site 1 (Pb: 32.7 mg/kg; Cd: 11.1 mg/kg; As: 4.1 mg/kg) and Site 2 (Pb: 22.0 mg/kg; Cd: 1.8 mg/kg). These concentrations exceeded permissible limits set by WHO/FAO, notably the 2.0 mg/kg safety threshold for lead (Food and Agriculture Organization of the United Nations & World Health Organization, 2011) and 0.1 mg/kg for cadmium and arsenic. Bioaccessibility tests showed substantial release in the intestinal digestate (Pb: 0.90 mg/L; Cd: 0.16 mg/L; As: 0.13 mg/L). Risk assessment based on a daily consumption of 115 g over 15 years indicated potential health concern. However, inconsistencies were identified between reported bioaccessibility values and hazard indices, requiring recalculation for final risk classification.
Conclusion
Kaolin consumed in Kimbanseke contains TMEs above international guideline limits. The intestinal solubilization of metals indicates potential absorption and systemic toxicity. Public health intervention is required to regulate kaolin exploitation and raise awareness among consumers.
References
Abrahams, P. W. (2002). Soils: Their implications for human health. Science of the Total Environment, 291(1–3), 1–32. https://doi.org/10.1016/S0048-9697(01)01102-0
Bahia Meroufel, S. (2015). Study of heavy metal pollution in sediments and clay soils (Doctoral dissertation, University of Oran).
Basta, N. T., Rodriguez, R. R., & Casteel, S. W. (2005). Bioavailability and risk assessment of oral exposure to geophagic materials. Journal of Hazardous Materials, 118(1–3), 155–164. https://doi.org/10.1016/j.jhazmat.2004.10.012
Bayiha, G. D. (2006). Geophagy in sub-Saharan Africa: Nutritional and toxicological aspects (Master’s thesis, University of Yaoundé).
Bonglaisin, J. N., Mbofung, C. M., & Lantum, D. N. (2015). Geophagy and heavy metals exposure: A review of health implications. International Journal of Environmental Research and Public Health, 12(8), 1000–1015. https://doi.org/10.3390/ijerph12081000
Caillet, C., Guerrit, K., & Villière, A. (2018). Impact of clay ingestion on the bioavailability of environmental contaminants. Environmental Pollution, 234, 562–571.
Callahan, G. N. (2003). Eating dirt: Is it a natural craving or a sign of disease? Emerging Infectious Diseases, 9(8), 1016–1021. https://doi.org/10.3201/eid0908.030033
Charrié, J.-P. (2007). Geology of clays and kaolins: Genesis and physicochemical properties. International Scientific Editions.
EFSA Panel on Contaminants in the Food Chain (CONTAM). (2009). Cadmium in food: Scientific opinion. EFSA Journal, 7(3), Article 980. https://doi.org/10.2903/j.efsa.2009.980
Food and Agriculture Organization of the United Nations & World Health Organization. (2011). Evaluation of certain food additives and contaminants: Seventy-third report (WHO Technical Report Series No. 960). World Health Organization.
Hooda, P. S., Henry, C. J., & Fowler, M. B. (2004). The potential impact of geophagy on the bioavailability of iron. Public Health Nutrition, 7(8), 1119–1124.
Hunter-Adams, J. (2016). Geophagy in South Africa: A review of the social and health implications. Journal of Public Health, 24(3), 201–210.
Kinyua, A. M., Atandi, J. G., & Mutegi, C. K. (2016). Trace element analysis of geophagic clays from Kenyan markets. Journal of Geochemical Exploration, 165, 1–10. https://doi.org/10.1016/j.gexplo.2016.03.001
Kutalek, R., Wewalka, G., & Gundacker, C. (2010). Geophagy and potential health implications in Uganda. Transactions of the Royal Society of Tropical Medicine and Hygiene, 104(12), 785–792.
Maitra, S. (2020). The cognitive dissonance of geophagy: Risk perception vs. pica craving. Journal of Health Psychology, 25(4), 512–525.
Mbayo, M. L., Kalonda, M. E., & Kasali, L. J. (2022). Evaluation of metallic contamination of kaolins sold in the markets of Kinshasa. Congo Review of Nuclear Sciences, 14(2), 45–58.
Musibono, D. E., Lubini, A., & Tshopo, P. (2010). Urban ecotoxicology in Kinshasa: Study of soils and sediments (Technical report). University of Kinshasa.
Naili, M., Hamdaoui, A., & Slimani, M. (2016). Toxicological assessment of clay ingestion: An experimental study. Journal of Applied Toxicology, 36(4), 541–550.
Naujokas, M. F., Anderson, B., & Suk, W. A. (2013). The broad scope of health effects from chronic arsenic exposure. Environmental Health Perspectives, 121(3), 295–302.
Needleman, H. (2004). Lead poisoning. Annual Review of Medicine, 55, 209–222. https://doi.org/10.1146/annurev.med.55.091902.103653
Oomen, A. G., Tolls, J., & Sips, A. J. (2003). Bioavailability of heavy metals in the human gastrointestinal tract. Environmental Science & Technology, 37(6), 1143–1150.
Pains, S., Leroy, P., & Dubois, M. (2016). Heavy metals and maternal health: A systematic review. Annals of Public Health, 22(1), 12–28.
Satarug, S., Garrett, S. H., & Sens, D. A. (2010). Cadmium, environmental exposure, and health outcomes. Environmental Health Perspectives, 118(2), 182–190.
Traoré, A. S. (2023). Geophagy and health risks in West Africa: The case of fumigated clays. African University Press.
Tuakuila, J. (2015). Lead and cadmium in blood and urine of the general population in Kinshasa, DR Congo. Journal of Trace Elements in Medicine and Biology, 32, 111–117. https://doi.org/10.1016/j.jtemb.2015.06.006
U.S. Environmental Protection Agency. (2011). Exposure factors handbook: 2011 edition. National Center for Environmental Assessment.
World Health Organization. (2011). Guidelines for drinking-water quality (4th ed.). World Health Organization.
World Health Organization. (2021). Lead: Health effects and prevention measures (Fact sheet No. 379).
Wragg, S. J., Cave, M. R., Basta, J. J., Klinck, B. A., & Taylor, H. (2011). The BARGE Unified Bioaccessibility Method. British Geological Survey (BGS).
Young, S. L. (2011). Craving earth: Understanding pica—the urge to eat clay, starch, ice, and chalk. Columbia University Press.
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