Cadmium and lead in geophagic clay consumed in Southern Nigeria: health risk from such traditional nutraceutical

Abstract

Geophagy is a cultural behavior, based on the recurrent intentional eating of clay soil, that is raising increasing concern as it implies multidimensional (space, time) potential risk of serious adverse health effects. This study investigated the level of toxic metals (Cd and Pb) in 20 Nigerian geophagic clays intended for both local consumption and distribution to the West Africa market. After sampling in 4 open markets in southern Nigeria (Akwa Ibom, Abia, Rivers, Imo), samples were subjected to digestion, ashing and analysis. The Pb levels in all samples exceeded the WHO/FAO maximum permissible limit of 0.1 mg kg^-1 whereas 16% exceeded the Cd limit of 0.3 mg kg^-1. The estimated daily intake of Pb for all samples ranged from 0.0032-0.0286 mg kg_bw^-1 day^-1 to 0.0024-0.0215 mg kg_bw^-1 day^-1 for children and adults, respectively. The estimated daily intakes for Cd ranged from bdl (below detection limit)-0.0010 mg kg_bw^-1 day^-1 to bdl-0.0028 mg kg_bw^-1 day^-1 for children and adults, respectively. In both cases, the WHO/FAO provisional Tolerable Weekly Intake is exceeded through the ingestion of these soils. Our results confirm health risks related to the geophagic practices, its role in exceeding health guidelines when considering aggregate exposure in the Nigerian scenario and body burden in developing organisms, young women, women at fertile age, and pregnant women. We discuss how geophagists consider clays as traditional nutraceuticals and how clarifying the nutraceutical role of geophagy could facilitate risk communication. Geophagic products are implicitly or explicitly marketed as dietary supplements, and as such they should be regulated (1) by labeling, and prohibition of scientifically unfounded health claims and (2) by safety standards before marketing. This is particularly critical when clays originate from countries living rapid, unplanned and uncontrolled development and dumped, like Nigeria.

Keywords: Geophagy; Heavy metals; Nutraceutical; Risk factors; Soil; West Africa.