Concentration of cadmium and lead in vegetables and fruits

Overview

Rusin and colleagues measured cadmium and lead in 370 retail samples of six fruit species (apple, cranberry, grape, pear, raspberry, strawberry) and four vegetable species (beetroot, celery, carrot, tomato) sourced from the Polish market, partitioned across four processing states (fresh, frozen, dried, processed). Concentrations were determined by graphite-furnace atomic absorption spectrometry against the TYG006RM vegetable-puree certified reference material under ISO/IEC 17025 conditions. Mean concentrations of both metals were highest in dried products on a dry-weight basis, and twelve samples (2 fruit, 10 vegetable) exceeded the EU cadmium (Cd) maximum permissible level while three vegetable samples exceeded the EU lead (Pb) maximum, with a single frozen tomato reaching 1074% of the 0.050 mg/kg Pb limit.

Key numbers

Sample structure (Table 1):

Type	Sample	Fresh	Dried	Frozen	Processed	Total
Fruit	Apple	57	10	–	20	87
Fruit	Cranberry	4	5	–	4	13
Fruit	Grape	15	11	–	4	30
Fruit	Pear	12	6	–	6	24
Fruit	Raspberry	7	4	4	4	19
Fruit	Strawberry	49	5	7	8	69
Vegetable	Beetroot	4	5	3	16	28
Vegetable	Carrot	12	7	13	4	36
Vegetable	Celery	21	4	5	9	39
Vegetable	Tomato	10	5	4	6	25
Total		191	62	36	81	370

Below-LOQ tallies (Results, p. 4): In fruits (n=242 total), Cd was below the LOQ in 87 samples and Pb in 96 samples. In vegetables (n=128 total), Cd was below the LOQ in 31 samples and Pb in 69 samples.

LOD / LOQ and CRM recovery (Table 4):

Analyte	Reference value (TYG006RM, µg/L)	LOD (µg/L)	LOQ (µg/L)
cadmium (Cd)	289 ± 10	0.2	0.35
lead (Pb)	203 ± 10	1.7	3.5

Cd and Pb in fruits — mean, SD, min, max (Table 6). Values in mg/kg fresh mass except dried rows in mg/kg dry weight (marked DW). A dash indicates the mean was below the LOQ for that sub-group.

Sample	Form	Cd mean	Cd SD	Cd min	Cd max	Pb mean	Pb SD	Pb min	Pb max
Apple	Dried (DW)	0.023	0.0138	0.009	0.039	0.127	0.0513	0.086	0.202
Apple	Fresh	0.001	0.0017	0.0004	0.0071	0.009	0.0059	0.001	0.024
Apple	Processed	0.001	0.0002	0.0004	0.001	0.009	0.0073	0.002	0.025
Cranberry	Dried (DW)	0.005	0.0039	0.0016	0.01	0.009	0.0028	0.0071	0.011
Cranberry	Fresh	0.008	0.0028	0.005	0.011	0.004	0.0012	0.003	0.005
Cranberry	Processed	0.006	0.0066	0.001	0.015	0.01	0.0007	0.009	0.01
Grape	Dried (DW)	0.001	0.0005	0.001	0.0021	0.047	0.0349	0.0038	0.1
Grape	Fresh	0.001	0.0006	0.0004	0.002	0.005	0.0031	0.0006	0.009
Grape	Processed	0.0004	—	0.0004	0.0004	0.07	0.0805	0.013	0.127
Pear	Dried (DW)	0.015	0.0008	0.015	0.016	0.036	0.0035	0.033	0.038
Pear	Fresh	0.004	0.0019	0.001	0.0073	0.008	0.0052	0.008	0.017
Pear	Processed	0.0008	0.0004	0.0005	0.001	0.0245	0.0213	0.004	0.047
Raspberry	Dried (DW)	0.116	0.0056	0.110	0.121	0.111	0.0266	0.092	0.129
Raspberry	Fresh	0.011	0.0065	0.003	0.021	0.012	0.0115	0.003	0.033
Raspberry	Processed	0.009	0.0087	0.002	0.019	0.011	0.0049	0.007	0.014
Raspberry	Frozen	0.026	0.0232	0.012	0.061	0.045	0.0204	0.031	0.06
Strawberry	Dried (DW)	0.131	0.1061	0.037	0.277	0.161	0.0409	0.097	0.201
Strawberry	Fresh	0.018	0.0152	0.0009	0.057	0.009	0.0069	0.002	0.027
Strawberry	Processed	0.003	0.0013	0.0008	0.004	0.006	0.0034	0.002	0.01
Strawberry	Frozen	0.016	0.0064	0.006	0.024	0.011	0.0015	0.009	0.012

Cd and Pb in vegetables — mean, SD, min, max (Table 7). Same units convention as Table 6.

Sample	Form	Cd mean	Cd SD	Cd min	Cd max	Pb mean	Pb SD	Pb min	Pb max
Beetroot	Dried (DW)	0.048	0.0222	0.021	0.072	0.115	0.2224	0.003	0.513
Beetroot	Fresh	0.235	0.3003	0.022	0.67	0.095	0.0559	0.056	0.135
Beetroot	Processed	0.022	0.0147	0.004	0.056	0.011	0.0069	0.001	0.02
Beetroot	Frozen	0.027	0.0235	0.01	0.054	0.173	—	0.173	0.173
Carrot	Dried (DW)	0.2	0.0997	0.086	0.331	0.206	0.1319	0.09	0.348
Carrot	Fresh	0.041	0.0146	0.024	0.062	0.027	0.0121	0.02	0.041
Carrot	Processed	0.034	0.0234	0.004	0.054	0.018	0.0152	0.004	0.034
Carrot	Frozen	0.036	0.0320	0.01	0.113	0.057	0.0551	0.008	0.117
Celery	Dried (DW)	—	—	—	—	0.259	—	0.259	0.259
Celery	Fresh	0.152	0.2251	0.0019	0.712	0.031	0.0267	0.003	0.074
Celery	Processed	0.03	0.0241	0.012	0.073	0.006	0.006	0.0015	0.01
Celery	Frozen	0.044	0.0137	0.026	0.062	0.064	0.0223	0.048	0.08
Tomato	Dried (DW)	0.103	0.1051	0.032	0.285	0.081	0.0745	0.028	0.133
Tomato	Fresh	0.003	0.0028	0.0006	0.0058	0.016	0.0239	0.0026	0.052
Tomato	Processed	0.038	0.0276	0.0059	0.067	0.031	—	0.031	0.031
Tomato	Frozen	0.019	0.0038	0.015	0.024	0.294	0.3443	0.05	0.537

Exceedances of EU maximum permissible levels (Table 5). Cd MPLs per Commission Regulation (EU) 488/2014 amending (EC) 1881/2006; Pb MPLs per Commission Regulation (EU) 2015/1005 amending (EC) 1881/2006. Percentages are the sample concentration expressed as a fraction of the MPL.

Commodity	Form	MPL Cd (mg/kg f.m.)	MPL Pb (mg/kg f.m.)	n Cd exceeded	n Pb exceeded	% MPL Cd	% MPL Pb
Raspberry	Frozen	0.050	0.10	1	–	122	–
Strawberry	Fresh	0.050	0.10	1	–	114	–
Beetroot	Fresh	0.10	0.10	2	1	203 / 670	135
Carrot	Frozen	0.10	0.10	1	1	113	117
Celery	Fresh	0.20	0.10	4	–	130 / 150 / 345 / 356	–
Tomato	Processed (Cd) / Frozen (Pb)	0.050	0.050	3	1	102 / 112 / 134	1074

Totals: Cd MPL exceeded in 12 samples (2 fruit, 10 vegetable); Pb MPL exceeded in 3 vegetable samples. The 1074%-of-MPL Pb result is a single frozen tomato sample at approximately 0.537 mg/kg fresh mass (matching the Table 7 frozen-tomato Pb maximum).

ANOVA across processing states (Table 8). Below-LOQ samples were excluded from each analysis; the number of excluded samples is in parentheses.

Variate	Group	n (excluded)	Sum of squares	Mean of squares	F	Pr(>F)	Significance
cadmium (Cd) in fruits	fresh/frozen/processed/dried	151 (86)	0.13887	0.00092	11.15	1.18×10⁻⁶	p < 0.001
cadmium (Cd) in vegetables	fresh/frozen/processed/dried	90 (34)	1.415	0.01572	4.049	0.0095	p < 0.01
lead (Pb) in fruits	fresh/frozen/processed/dried	140 (93)	0.1030	0.00074	56.59	< 2×10⁻¹⁶	p < 0.001
lead (Pb) in vegetables	fresh/frozen/processed/dried	55 (69)	0.5223	0.00950	7.138	0.000392	p < 0.001

Outlier analysis (Figure 1, narrative on p. 6). Dried fruits Cd: two outliers at 0.277 and 0.210 (strawberry max and likely raspberry/strawberry). Fresh vegetables Cd: six outliers at 0.203, 0.670, 0.260, 0.690, 0.300, 0.712 (concentrated in beetroot and celery rows). Processed fruits Pb: two outliers at 0.127 and 0.047 (grape processed maximum and a pear processed value). Frozen vegetables Pb: one outlier at 0.537 (frozen tomato).

Tukey HSD post-hoc summary (Figure 2 and p. 8). For Cd in fruits, dried-fruit means differ significantly from fresh, frozen, and processed means. For Cd in vegetables, fresh and processed means differ; frozen versus fresh is significant only at the 10% level. For Pb in fruits, dried-fruit means differ significantly from fresh, frozen, and processed. For Pb in vegetables, processed-versus-dried is highly significant, with fresh-versus-dried and processed-versus-frozen also significant.

Methods (brief)

Graphite-furnace AAS on a SavantAA Sigma spectrometer with PAL3000 autosampler and a GF3000 graphite furnace (GBC, Australia), with background correction, wavelengths 228.8 nm (Cd) and 217 nm (Pb), and lamp currents 5.0 mA (Cd) and 0.3 mA (Pb) (Table 3). Sample preparation followed consumption practice (washing, peeling, removal of inedible parts) before homogenisation on a T18 Digital Ultra-Turrax (IKA, Germany) for fresh and frozen samples and on a Testchem PZS 01 vibratory grinder (Poland) for dried samples; processed liquids were mixed and syrup/marinade products were separated and homogenised. Sample weights: 2 g for fresh/frozen, 1 g for dried, 2 g for processed, 10 g for liquids; 8 mL HNO₃ (65%, Suprapur, Merck, Germany) was added to all samples and dried samples received an additional 1 mL of 30% H₂O₂. Mineralisation used a four-phase microwave program on a Magnum II microwave digester (Ertec, Poland) (Table 2). Calibration used SPEX CertiPrep 1000 mg L⁻¹ Cd and Pb standards in 2% HNO₃ (R² = 0.999 for both metals; Table 3). Method performance was verified against TYG006RM vegetable-puree CRM. LODs were estimated as mean blank signal + 3 SD and LOQs as mean blank signal + 6 SD (Cd LOD 0.2 µg/L, LOQ 0.35 µg/L; Pb LOD 1.7 µg/L, LOQ 3.5 µg/L). Sampling and analysis followed Regulation (EC) 882/2004 and Regulation (EC) 333/2007. Statistics used ANOVA at α = 0.05, boxplot-based outlier analysis, and Tukey HSD post-hoc tests with Bonferroni correction for multiple comparisons; below-LOQ values were excluded from the variance analyses.

The paper reports Cd and Pb only; no other metals were measured. Cadmium and lead are both reported as total elemental concentrations (no speciation). Cranberry samples were drawn from Vaccinium macrocarpon Aiton (the American cranberry). Concentrations for fresh, frozen, and processed products are on a fresh-mass basis; dried-product concentrations are on a dry-weight basis and are not directly comparable to the EU MPLs (which are framed on a fresh-mass basis), so the per-row exceedance counts in Table 5 are restricted to fresh, frozen, and processed samples.

Implications

Certification: Contributes Polish retail-market occurrence data for Cd and Pb across ten produce commodities in four processing states (n=370), with explicit MPL-exceedance counts against the EU 488/2014 (Cd) and 2015/1005 (Pb) limits. The fresh-beetroot Cd distribution (mean 0.235 mg/kg f.m., max 0.67) and the fresh-celery Cd distribution (mean 0.152 mg/kg f.m., max 0.712) are the highest within-group means in the vegetable dataset and are relevant to upper-tail percentile estimation for root-and-tuber and stem vegetable product categories. The 0.537 mg/kg frozen-tomato Pb outlier is a single sample but contributes to upper-percentile sensitivity for frozen vegetable matrices.

Courses: Useful case study for two distinct teaching points — (i) how dry-weight reporting can make dried products look anomalously high when juxtaposed against fresh-mass MPLs, requiring explicit basis conversion before any threshold comparison; and (ii) how single-sample exceedance can dominate a small-n subgroup (the 0.537 mg/kg frozen tomato Pb result is the entire signal for the frozen-tomato Pb category). Methodologically, the paper is a reproducible example of ISO 17025–accredited GFAAS measurement with CRM-verified recovery.

App: Contributes occurrence data for Polish-origin fresh, frozen, dried, and processed forms of apple, pear, grape, raspberry, strawberry, cranberry, beetroot, celery, carrot, and tomato to the cadmium and lead profiles for each commodity ingredient. Processing-form must be tracked separately in any per-ingredient model because dried-versus-fresh concentrations differ by roughly the water-removal factor.

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