Saleem et al. 2025 — Heavy metals in 13 locally grown vegetables from a Grand Forks (North Dakota) farmer’s market
Saleem and colleagues analyzed 82 vegetable samples (13 locally grown species) from the Town Square Farmer’s Market in Grand Forks, North Dakota, for 15 elements (Na, Mg, K, Ca, Fe, Se, Mn, Cu, Zn, Co, Cr, Ni, As, Cd, Hg, Pb). The study reports per-vegetable means and SDs, computes EDI, THQ/HI, and TCR per metal per vegetable, and contrasts leafy vs fruit vegetables. Spinach showed the highest total metal accumulation; Cd levels exceeded FAO/WHO maximum allowable concentrations in most vegetable species in the sample set.
Key numbers
- n=82 samples across 13 vegetable species (Methods, Section 2.1). Per-species sample counts (Table 2): potato 8; onion 7; tomato 7; sugar beet 7; green chili 7; dill 5; corn 7; spinach 5; white eggplant 5; kale 5; green bean 7; capsicum 6; cucumber 6.
- All concentrations reported in µg/g dry weight (Methods).
- Total mean concentration trend across all vegetables: K > Mg > Na > Ca > Fe > Mn > Zn > Cu > Ni > Cd > Se > As > Co > Cr > Pb > Hg.
- Reported toxic-metal ranges across vegetable species (Table 1): mercury 0.0008–0.0113 µg/g; chromium 0.014–0.179 µg/g; nickel 0.342–2.139 µg/g; arsenic 0.009–0.436 µg/g; cadmium 0.006–0.985 µg/g; lead 0.007–0.081 µg/g.
- Per-vegetable mean (SD) toxic metals (Table 1, µg/g dry weight):
- Potato: As 0.010 (0.002); Cd 0.218 (0.087); Pb 0.009 (0.003); Hg 0.0017 (0.0009); Cr 0.014 (0.005); Ni 0.535 (0.206).
- Onion: As 0.058 (0.055); Cd 0.080 (0.033); Pb 0.014 (0.007); Hg 0.0010 (0.0002); Cr 0.032 (0.021); Ni 0.400 (0.245).
- Tomato: As 0.022 (0.011); Cd 0.369 (0.101); Pb 0.007 (0.003); Hg 0.0029 (0.0017); Cr 0.030 (0.020); Ni 0.484 (0.223).
- Sugar beet: As 0.090 (0.087); Cd 0.245 (0.153); Pb 0.018 (0.016); Hg 0.0009 (0.0002); Cr 0.042 (0.043); Ni 0.349 (0.128).
- Green chili: As 0.048 (0.025); Cd 0.657 (0.442); Pb 0.007 (0.003); Hg 0.0008 (0.0001); Cr 0.033 (0.025); Ni 0.975 (0.284).
- Dill: As 0.079 (0.024); Cd 0.286 (0.075); Pb 0.040 (0.035); Hg 0.0047 (0.0002); Cr 0.061 (0.019); Ni 1.270 (0.685).
- Corn: As 0.013 (0.009); Cd 0.006 (0.004); Pb 0.007 (0.000); Hg 0.0012 (0.0004); Cr 0.019 (0.009); Ni 0.366 (0.172).
- Spinach: As 0.064 (0.016); Cd 0.985 (0.223); Pb 0.081 (0.013); Hg 0.0113 (0.0035); Cr 0.179 (0.063); Ni 0.342 (0.070).
- White eggplant: As 0.190 (0.075); Cd 0.453 (0.061); Pb 0.010 (0.013); Hg 0.0009 (0.0002); Cr 0.021 (0.013); Ni 0.922 (0.264).
- Kale: As 0.039 (0.010); Cd 0.105 (0.021); Pb 0.021 (0.003); Hg 0.0077 (0.0009); Cr 0.114 (0.088); Ni 0.365 (0.058).
- Green bean: As 0.009 (0.001); Cd 0.014 (0.025); Pb 0.009 (0.004); Hg 0.0020 (0.0013); Cr 0.024 (0.008); Ni 2.139 (0.774).
- Capsicum: As 0.027 (0.023); Cd 0.411 (0.304); Pb 0.008 (0.007); Hg 0.0017 (0.0001); Cr 0.028 (0.011); Ni 0.712 (0.333).
- Cucumber: As 0.436 (0.145); Cd 0.045 (0.025); Pb 0.021 (0.013); Hg 0.0023 (0.0013); Cr 0.034 (0.013); Ni 0.713 (0.274).
- Spinach showed maximum concentrations of Cd, Cr, Pb, and Hg across the sampled vegetables (Section 3.1).
- Highest Ni in green bean (2.139 µg/g); highest As in cucumber (0.436 µg/g); lowest Pb in corn, tomato, green chili (0.007 µg/g).
- Hazard Index (Table 4) above 1 in all 13 vegetables, ranging 1.59 (corn) to 18.3 (spinach); Cd, Co, As are major non-carcinogenic risk contributors with THQ>1 in most vegetable species.
- Target cancer risk (Table 5) — Ni TCR > 1×10⁻⁴ in all vegetables (range 1.8×10⁻³ to 1.0×10⁻²); As TCR > 1×10⁻⁴ for onion, tomato, sugar beet, green chili, dill, spinach, white eggplant, kale, capsicum; Cd TCR > 1×10⁻⁴ for the same eight (plus dill, spinach); Pb TCR < 1×10⁻⁶ for all vegetables.
Methods (brief)
Vegetables were collected June–September from the Town Square Farmer’s Market in Grand Forks, North Dakota. 2–3 sub-samples (~0.2–0.5 kg each) of each vegetable species were collected from different vendors and pooled per representative sample. Samples were washed with deionized water, air-dried 24 h, homogenized, ground, and oven-dried at 70–80 °C to constant weight. 0.5 g dried ground vegetable was digested with 5 mL concentrated HNO3 in a Milestone UltraWAVE following EPA method 3051A (Revision 1); final volume 50 mL. Quantification for Na, Mg, K, Ca, Fe, Se, Mn, Cu, Zn, Co, Cr, Ni, As, Cd, Pb used a Thermo Scientific iCAP Qc ICP-MS in kinetic energy discrimination (KED) mode following EPA method 200.8 (Revision 5.4); Sc, Rh, and Bi used as internal standards. Mercury was quantified separately on homogenized, ground, oven-dried solid using a Milestone DMA-80 Tri Cell direct mercury analyzer per EPA method 7473. All measurements done in triplicate. QA/QC used SRM NIST 1567b (recovery >85% for most elements), duplicates (RPD <20%), reagent blanks, and blank spikes. EDI calculated using 0.34 kg/person/day vegetable consumption and 70 kg adult body weight. The paper does not perform speciation; tAs and tHg are reported (arsenic from ICP-MS, mercury from DMA-80). Cr reported as total Cr (no Cr-VI speciation).
Implications
- Certification (HMTc): Adds 82 USA farmer’s-market vegetable samples (13 species) of Cd, Pb, tAs, tHg, Cr, Ni occurrence data on dry-weight basis. Spinach values represent a heavy-leafy outlier; ingredient-page profiles for spinach, dill, kale, green chili, tomato, sugar beet, and capsicum are particularly informed by this source.
- Courses: Suitable as a farmer’s-market / locally-sourced produce case study for QA and supply-chain audiences; the Cd elevation in tomato, capsicum, white eggplant relative to FAO/WHO 0.05 mg/kg fruit-vegetable limit is a teachable point.
- App: Contributes Cd, Pb, tAs, Cr, Ni occurrence data points to spinach, tomato, potatoes, onions, corn, cucumber, green-beans, and dried-herbs (dill, kale).
Wiki pages this source may touch
- vegetables
- spinach
- tomato
- onions
- potatoes
- corn
- cucumber
- green-beans
- dried-herbs
- cadmium
- lead
- arsenic-total
- mercury-total
- chromium
- nickel
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.