See et al. 2025 — Heavy metals in leafy vegetables from Selangor wet market, Malaysia
This 2025 Malaysian market survey measured Al, Cd, Cr, Cu, Fe, and Pb in four commercially important leafy vegetables (cabbage, mustard, spinach, and pak choi) purchased from Pasar Borong Selangor, one of the largest wholesale wet markets in the Klang Valley region, using ICP-OES. The notable finding is that Cd, Cr, Cu, and Pb were all undetected in all samples (below detection limits of <0.004 mg/kg for Cd and Pb, <0.01 mg/kg for Cr and Cu), while Al and Fe were detected at levels within FAO/WHO permissible limits, with spinach consistently showing the highest concentrations of both metals. Health risk assessment via target hazard quotient (THQ) and hazard index (HI) confirmed low non-carcinogenic risks across all vegetables and metals for the adult population.
Key numbers
Heavy metal concentrations (mg/kg fresh weight):
| Metal | Cabbage | Mustard | Spinach | Pak choi | FAO/WHO limit (mg/kg) | Malaysian limit (mg/kg) |
|---|---|---|---|---|---|---|
| Al | 11.12±3.76 | 28.97±5.33 | 41.37±8.53 | 25.69±6.32 | 2.0 PTWI basis | N/A |
| Cd | ND (<0.004) | ND | ND | ND | 0.2 (leafy veg) | 1.0 |
| Cr | ND (<0.01) | ND | ND | ND | 2.3 | N/A |
| Cu | ND (<0.01) | ND | ND | ND | 73.3 | N/A |
| Fe | 6.30±5.78 | 4.12±1.84 | 13.59±4.73 | 4.14±0.31 | 425.5 | N/A |
| Pb | ND (<0.004) | ND | ND | ND | 0.3–2.0 | 0.3 (Malaysian Food Reg. 1985) |
Note: All values are fresh weight. Al comparison against FAO/WHO JECFA PTWI (2 mg/kg body weight/week, set June 2011). LODs: Cd and Pb <0.004 mg/kg; Cr and Cu <0.01 mg/kg.
Rank order for detected metals: Al: spinach > mustard > pak choi > cabbage. Fe: spinach > cabbage ≈ pak choi > mustard.
Estimated Daily Intake (EDI) at 240 g/day vegetable consumption:
- Al: cabbage 3.241×10⁻³ mg/day; mustard 8.443×10⁻³; spinach 12.056×10⁻³; pak choi 7.487×10⁻³ mg/day
- Fe: cabbage 1.816×10⁻³ mg/day; mustard 1.201×10⁻³; spinach 3.961×10⁻³; pak choi 1.206×10⁻³ mg/day
- All EDI values below maximum tolerable daily intakes
Target Hazard Quotient (THQ) and Hazard Index (HI):
- All THQ values <1 for Al and Fe (only detected metals); Cd, Cr, Cu, Pb THQ not calculable (not detected)
- HI values: cabbage 0.005864; mustard 0.0102; spinach 0.01772; pak choi 0.00921
- Global THQ for Al = 0.03123; for Fe = 0.01172 — all well below threshold of concern
Methods (brief)
ICP-OES (Avio 550 Max, PerkinElmer) with HTS flow injection sample introduction. Microwave acid digestion using 9 mL HNO3 + 3 mL HCl at 180°C for 45 min (MARS-6 system). All calibrations with r² ≥0.998. Results reported as fresh weight (FW). Vegetable samples washed in running water then 3× distilled water before analysis. Edible portions only. Statistical analysis by one-way ANOVA and Pearson correlation (Minitab 21.1). Health risk calculations follow Chen et al. (2011) EDI formula with standard Malaysian reference body weight of 70 kg.
Study limitations: Small sample size (n=3 per vegetable type, single wet market, 3-week collection window); does not capture inter-seasonal or inter-source variation; only evaluates edible portion after washing (surface contamination partially removed); health risk calculations assume 240 g/day vegetable intake and do not assess children or other vulnerable groups.
Implications
Certification: This study documents non-detection of Cd and Pb in four commonly consumed leafy vegetables from a major Malaysian urban wholesale market — a positive baseline finding. However, the authors note that other Malaysian studies (Sulaiman et al. 2020 in Pahang) found As and Pb in leafy vegetables from agricultural areas at concerning levels, suggesting that market origin matters significantly.
Courses: Illustrates the principle that market-point surveillance of leafy vegetables in urbanized Malaysia may show lower contamination than farm-gate or agricultural-area surveys, due to sourcing from cleaner growing regions (Cameron Highlands suppliers). Al is a notable exception — spinach accumulates Al at levels requiring further investigation relative to JECFA tolerable intakes.
App: Pak choi, cabbage, mustard greens, and spinach from Malaysian market sources: Cd and Pb as data gaps (below detection in this study); Al is a relevant analyte for spinach specifically. Context-dependency (urban market sourcing vs. near-farm sampling) is a key uncertainty flag.