Overview
Adebayo and coauthors measured cadmium, chromium, copper, manganese, nickel, and lead in irrigation wastewater and wastewater-grown African spinach from Railway Quarters in Bauchi, Nigeria. The paper is routeable for spinach occurrence evidence because it reports mean concentrations in the edible vegetable sample and a health-risk calculation based on local spinach consumption.
Key numbers
Table 1 reports heavy metals in Railway Quarters irrigation wastewater as mean +/- standard error, with units of ug/cm3:
Table 2 reports heavy metals in the spinach sample as mean +/- standard error, with units of mg/kg:
| Metal | Spinach concentration (mg/kg) |
|---|---|
| cadmium (Cd) | 1.00 +/- 0.00 |
| chromium (Cr) | 1.65 +/- 0.00 |
| Cu | 7.70 +/- 0.00 |
| Mn | 12.65 +/- 0.00 |
| nickel (Ni) | 7.70 +/- 0.00 |
| lead (Pb) | 6.60 +/- 0.00 |
Table 3 reports daily intake of metals (DIM), reference oral dose (RfD), health risk index (HRI), and transfer factor. The abstract reports HRI values of 0.3000 for cadmium (Cd), 0.0003 for chromium (Cr), 0.2150 for Cu, 0.1240 for Mn, 0.1250 for nickel (Ni), and 0.5000 for lead (Pb), all below the authors’ HRI cutoff of 1.0.
The authors compare the measured spinach lead value of 6.60 mg/kg with an Indian Standard safe limit of 2.50 mg/kg and state that the lead level is above that comparison value. The concentration values should be treated as Nigerian wastewater-irrigated spinach context, not as a U.S.-market benchmark distribution.
Methods (brief)
The study collected wastewater and African spinach from the Railway Quarters irrigation farm in Bauchi, Nigeria. Edible vegetable parts were washed, air-dried, ground, sieved, and digested from a 1.00 g ground sample using a 5:1:1 mixture of nitric acid, sulfuric acid, and perchloric acid. Wastewater was digested from a 50.00 cm3 sample using concentrated nitric acid. The digests were analyzed by Bulk Scientific Atomic Absorption Spectrophotometer Model 210 VGP.
The paper reports total metals only. It does not provide arsenic speciation, mercury speciation, LOD/LOQ, sample-level replicates, or moisture-basis conversion. The spinach values are therefore routeable as source-reported mg/kg on the study’s dried/processed analytical basis, with basis caveats preserved.
Implications
Certification: The source supports spinach contamination context for Cd, Cr, Cu, Mn, Ni, and Pb under wastewater-irrigated conditions in Nigeria. It should not be pooled silently with U.S. market spinach because geography, irrigation source, and basis differ.
Courses: The source is a compact example of why wastewater irrigation can produce routeable produce measurements while still requiring jurisdiction and basis flags before benchmark pooling.
App: The study can inform a spinach risk explainer that distinguishes field contamination pathways from retail-market representativeness.
Related evidence
Update history
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