Geophagic clay materials from Nigeria: a potential source of heavy metals and human health implications in mostly women and children who practice it
- 299 Downloads
Geophagy is a common practice among certain cultural groups especially women in some rural communities in Nigeria. The safety of eating such clays in terms of their heavy metal composition has not been ascertained, neither is the link between them and disease conditions established in geophagists. The analysis of field survey data reveals that the majority (about 90 %) of the women did not go beyond secondary school education. The geology of an area has a direct influence on the chemical composition of the soils. Therefore, this research was carried out to determine the mineralogical and the heavy metal content of some geophagic clay materials from Nigeria. All the geophagic clay materials are hydrated silicates of either Al, (Na and Ca), (Al and Mg), or/and (Mg and Fe). The concentration levels of Na, Al, Ca, Fe, Mg, Cu, and Zn are tolerable and apparently could serve as a veritable source of mineral nutrients deficient in the human body. An assessment of the level of contamination of heavy metals on the basis of the index of geo-accumulation (I geo) shows that Cr, Cu, Zn, Co, and Ni (all with I geo < 1) did not contaminate the clay materials. On the contrary, they are extremely contaminated by As, Cd and Se (I geo = >5), and are moderately to strongly contaminated by Pb and Sb (I geo = 2–3). In terms of health risk assessment, the presence of heavy metals such as As, Cd, Pb, Se, and Sb with a health risk index (HRI) >1, renders the geophagic clays unsafe for human consumption. Similarly, Al, Fe, and Na are in excess in the clay (HRI ⋙ 1) posing serious human health risks. Thus, the ingestion of geophagic clay materials by pregnant women and children when it contains heavy metals like Pb, As, Cd, Se, and Sb poses the risk of some medical disorders and should therefore be considered a public health problem. Since geophagic practice will persist despite civilization, we advocate finding ways of reducing heavy metal pollutants in geophagic clays through suitable remediation technology.
KeywordsGeophagy Heavy metals Contamination Women Children Health risk
This study is part of on-going research on geophagia in Nigeria supported by self-funding. The authors seek funding to continue this noble project. We thank Prof. T.C. Davies for debuting this research in Nigeria and for his encouragement. We also thank the anonymous reviewers for making this paper worthwhile. The University of Jos, Nigeria, our host, is also appreciated for making the work possible.
- Bisi-Johnson, M. A., Obi, C. L., & Ekosse, G. E. (2010). Microbiological and health-related perspectives of geophagia: An overview. African Journal of Biotechnology, 9(19), 5784–5791. http://www.academicjournals.org/AJB
- Crawford, L., & Bodkin, K. (2011). Health and social impacts of geophagy in Panama. McGill Science Undergraduate Research Journal, 6(1). http://msurj.mcgill.ca/vol6/iss1/crawford2011.pdf.
- Danford, D. E., Smith, J. C., & Huber, A. M. (1982). Pica and mineral status in the mentally retarded. American Journal of Clinical Nutrition, 35, 958–967.Google Scholar
- Davies, T. C. (2010). Medical geology in Africa. In O. Selinus, R. B. Finkelman, & J. Centeno (Eds.), Medical geology—a regional synthesis, chapter 8, 1st ed. (pp. 199–219). Amsterdam, The Netherlands: Springer, 559 p.Google Scholar
- Davies, T. C., Lar, U. A., Solomon, A. O., & Abraham, P. W. (2008). Mineralogy and geochemistry of geophagic materials consumed in Jos-Plateau State of Nigeria. Paper presentation at International Conference South Africa.Google Scholar
- Dominy, N. J., Davoust, E., & Minekus, M. (2004). Adaptive function of soil consumption: An in vitro study modeling the human stomach and small intestine. Annual Review of Nutrition, 207, 319–324.Google Scholar
- Ekosse, E. G., & Jumbam, N. D. (2010). Geophagic clays their mineralogy, chemistry and possible human health effects. African Journal of Biotechnology, 9(40), 6765.Google Scholar
- Environmental Health Criteria (EHC) 231 (2005). Bentonite, Kaolin and selected clay minerals. In Z. Adam’s, R. Williams, & J. Fodoe (Eds.), International programme on chemical safety, inter-organization programme for the sound management of chemicals. A comprehensive agreement published under joint sponsorship of UNEP, ILO, FAO, WHO, UNIDO, UNITAR and OECD, WHO Geneva.Google Scholar
- Ford, S. O. (1980). The economic mineral resources. In A. Vogel (Ed.), Jour & earth evolution Sci. 2/1981. Publ. Fredr. Berlin: Vieweg and Sohn.Google Scholar
- Fordyce, F. M., Johnson, C. C., Navaratne, U. R. B., Appleton, J. D., & Dissanayake, C. B. (1998). Studies of selenium geochemistry and distribution in relation to iodine deficiency disorders in Sri Lanka. British Geological Survey Overseas Geology Series Technical Report WC/98/28.Google Scholar
- Hladik, C. M., & Gueguen, L. (1974). Geophagy and mineral nutrition in wild primates. CR Academic Sciences (D) (Paris), 279, 1393–1396.Google Scholar
- Izugbara, C. O., & Emmanuel, C. J. (2003). The cultural context of geophagy among pregnant and lactating Ngwa women of Southeastern Nigeria. The African Anthropologist, II(2). http://wings.buffalo.edu/research/anthrogis/JWA/V2N2/izugbara-daru-art.pdf.
- Johns, T., & Duquette, M. (1991). Detoxification and mineral supplementation as functions of geophagy. American Journal of Clinical Nutrition, 53, 448–456.Google Scholar
- Kasper, D. L., Braunwald, E., Fauci, A. S., Hauser, S. L., Longo, D. L., Jameson, J. L., et al. (Eds.). (2005). Harrison’s Principles of internal medicine (16th ed.). New York: McGraw Hill.Google Scholar
- Muller, G. (1981). Die Schwermetallbelstang der sediment des Neckarars und seiner N ebenflusseeine estandsaufnahme. Chemical Zeitung, 105, 157–164.Google Scholar
- Pfeiffer, C. C., & Mailloux, B. S. (1987). Excess copper as a factor in human diseases. Journal of Orthomolecular Medicine, 2(3). http://orthomolecular.org/library/jom/1987/pdf/1987-V02n03-p171.pdf.
- U.S. Environmental Protection Agency (US EPA) (1989). Risk assessment guidance for superfund: Human health evaluation manual (pat A): Interim Final U.S. Environmental Protection Agency, Washington, DC, USA (EPA/540/1-89/002).Google Scholar
- Vermeer, D. E. (1964). Agricultural and dietary practices among the Tiv, Ibo and Birom tribes, Nigeria Ph.D Thesis, University of Berkeley, USA.Google Scholar
- Vermeer, D. E., & Ferrell, R. E. (1985). Nigerian geophagical clays, a traditional anti diarrhea. Pharmaceutical Sciences, 1227, 364–366.Google Scholar
- World Health Organization. (1993). Guidelines for drinking water quality (2nd ed.). Geneva: World Health organization.Google Scholar
- Zafar, T. A., & Weaver, C. M. (1999). Effects of aluminum on calcium absorption, growth and bone calcium content. International Journal of Agriculture and Biology, 2, 138–141.Google Scholar