keywords: Cadmium, edible clay, heavy metals, mercury, permissible limit
This study was undertaken to determine and compare the level of heavy metals- zinc, lead, cadmium, copper, mercury and cobalt in two species of edible clay (Nzu and Ulo) sold in four major markets namely; Ochanja, Ose, Relief and Okpoko, in Onitsha metropolis of Anambra state, Nigeria. Heavy metals in the edible clay samples were analysed by atomic absorption spectrophotometry. Mean concentrations were computed from three replicate measurements. Data from the markets were compared by One-Way ANOVA while data between the clay types were analyzed by independent t-test. The result of the study indicate that mean concentrations (ppm) of Zn, Pb, Cd, Cu, and Co showed no significant difference [(P =.981, .479, .335, .333 and .613) for Zn, Pb, Cd, Cu, and Co respectively] among markets. The mean concentration (ppm) of Hg (2.335±0.276) in Ochanja market however, differ significantly (P =.045) from those of the other markets, 0.621±0.244, 0.796±0.280 and 0.251±0.190 for Ose, Relief and Okpoko, respectively. Statistically reliable differences were found for Zn (P =.000) and Co (P =.003) type 1(nzu) and 11 (ulo) mean concentrations. However, mean concentrations of Pb, Cd, Cu and Hg in type 1 and type 11 clays did not differ significantly [(P =.391, .288, .243, and .613) for Pb, Cd, Cu and Hg, respectively]. There were high concentrations of Hg in virtually all samples and Cd in few samples. The high levels of Cd and Hg in the analyzed edible clays make them unhealthy for human consumption. However, further research is required to validate the reliability of these findings.
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