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Heavy metal contamination of selected spices obtained from Nigeria
GAYA, U.I. & IKECHUKWU, S.A.
Abstract
In this study, the levels of trace metals (Cd, Cr, Cu, Co, Fe, Mn, Ni, Mo, Pb,
Zn) in twenty two spices representing four spice groups (seeds, bulbs, leaves, fruit pods and
rhizome) from a major market in Northern Nigeria were determined using atomic absorption
spectroscopy, and assessed based on regulatory standards. Garlic exhibited the highest zinc
concentration (21.733 ±0.044 mg/kg), which falls lower than the upper toxic level for most
plants. Lead concentrations peaked in African nutmeg (4.717 ± 0.017 mg/kg) but are lower
than the normative for the final dosage form of medicinal plants. The daily intake-based
hazard of the spices was assessed using the minimum risk levels set by WHO, and the
FAO/WHO maximum tolerable intake limits. All the spices contain excessive cobalt and
copper with maximum levels (mg/kg) in ginger cobalt (11.117±0.069) and African nutmeg
(15.300 ± 0.041), respectively. The estimated daily intake values (μg/kg day) of onion (1.10),
ginger (12.00), utazi (1.30), alligator paper (1.20), garlic (0.89), Ashanti leaves (0.88), castor
seeds (1.20), and shallot (0.86)were higher than the provisional maximum tolerable intake set
by FAO/WHO, constituting a potential risk to human health. These results show that spices
can accumulate exceeding levels of toxic metals whose potential risk to human health should
be given priority. © JASEM
Keywords
heavy metal; contamination; Nigeria; spices; health; daily intake
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