Ahmed et al. 2023 — Trace metals in wastewater-irrigated tomatoes, Cairo
This study measures trace metal concentrations in tomato fruits grown on farms irrigated with industrial wastewater near Cairo, Egypt, and performs a health risk assessment using hazard quotients (HQ) for multiple metals. The study also measures metals in irrigation water and soil at the same farms to characterize the contamination source and pathway.
Key numbers
Tomato fruit concentrations (reported values, wet weight assumed unless stated):
- Pb: 360.7 mg/kg — this is exceptionally high. Note: this value is likely to be in µg/kg (ppb) rather than mg/kg (ppm) based on typical food matrix concentrations; verify against original tables. If mg/kg is correct, it represents extreme wastewater contamination far beyond any regulatory limit.
- Cd: reported; exact mean not extracted from abstract alone; present in the data.
- Cr: reported; see full paper tables.
- Ni: reported; see full paper tables.
The paper notes that hazard quotients for several metals exceeded 1 (i.e., non-carcinogenic risk threshold) for adult and child consumers, indicating meaningful health risk from consuming these wastewater-irrigated tomatoes.
Irrigation water contained elevated Pb, Cd, Cr, and Ni consistent with industrial effluent contamination. Soil concentrations exceeded Egyptian background values.
Methods (brief)
Samples collected from multiple farms in Cairo irrigated with industrial wastewater. Tomato fruits, soil, and irrigation water collected simultaneously. Acid digestion of plant and soil samples; ICP-OES or AAS measurement. Health risk assessment using USEPA hazard quotient approach: HQ = (estimated daily intake) / (reference dose). Concentration units require verification from full paper tables (reported as mg/kg in some summaries, possibly meaning µg/kg in actual analytical context).
Limitation: Wastewater-irrigated farms represent a worst-case contamination scenario; values are not representative of mainstream commercial tomato production. Geographic scope limited to Cairo periurban area with known industrial wastewater contamination.
Implications
Certification: Illustrates the upper range of Pb and Cd contamination possible in tomatoes under wastewater irrigation — supply-chain screening for irrigation water source is a critical lever. HQ >1 for multiple metals documents real health risk, not theoretical.
Courses: Strong case study for supply-chain contamination module; demonstrates the farm-to-fork contamination pathway from industrial wastewater through irrigation to edible fruit.
App: High-contamination outlier scenario. These values should not be used as typical contamination_profile values for tomatoes; they are sourcing-risk flags for specific production contexts.
Microbiome: Not applicable.