Kowalska 2021 — Heavy metals in Polish herbs, spices, tea, and coffee
This Polish study measured Cd, Pb, As, and Hg in 240 plant material samples — 163 herb samples across 37 species, 61 spice samples across 12 species, 8 green China tea samples, and 8 roasted Arabica coffee bean samples — collected 2015–2018. Analysis was by ICP-MS (Cd, Pb, As) and mercury analyzer AMA 254 (Hg). Lead showed the highest contamination range overall (0.010–5.680 mg/kg), while mercury was uniformly low (0.005–0.030 mg/kg). Among herbs, 24 samples (18% of 131 herb samples that had data) exceeded the WHO limit for Pb (10 mg/kg) only when interpreted against some measures, though against the most commonly cited 10 mg/kg WHO limit no exceedances occurred — however, significant exceedances of the EU fresh-herb-converted limits did occur in many samples. No spice, tea, or coffee sample exceeded any limit for any metal. Noncarcinogenic risk (TTHQmax) was below 1 for all categories; carcinogenic risk from As was below 10⁻⁴ for all categories.
Key numbers
All concentrations in mg/kg dry matter (DM) unless noted.
LOD/LOQ (mg/kg): Hg: LOD 0.002, LOQ 0.005; Cd: LOD 0.01, LOQ 0.02; Pb: LOD 0.005, LOQ 0.01; As: LOD 0.05, LOQ 0.1
Overall range by category:
- Herbs + spices: 0.005–5.680 mg/kg (all metals combined range)
- Tea + coffee: 0.005–0.791 mg/kg
Lead — herbs (n=163):
- Range: <LOQ (0.010) to 5.680 mg/kg DM
- Highest Pb species: valerian root (mean 1.730, max 5.680), lemon balm leaves (mean 1.91, max 3.47), common sage leaves (mean 2.21, max 2.55), southernwood (mean 1.57, max 1.85), blackthorn flowers (mean 1.341), chamomile flowers (mean 1.572)
- 24 samples (18%) exceeded the 0.3 mg/kg limit applied in the context of fresh herbs converted to dry weight equivalents at 90% moisture content (per EU Reg 420/2011)
Lead — spices (n=61):
- Basil (green matter, n=3): mean 1.66 mg/kg Pb, range 1.34–1.92 (highest Pb in spice group, below EU limit for dried herbs of 2.0 mg/kg)
- Black pepper (n=26): mean 0.159 mg/kg Pb, range <LOQ to 0.740; mean As 0.053 mg/kg, range <LOQ to 0.863
- Peppers/capsicum (n=8): mean 0.338 mg/kg Pb, mean 0.077 mg/kg As
- Allspice (n=3): mean 0.361 mg/kg Pb
- Cumin (n=3): mean 0.43 mg/kg Pb, mean Cd 0.072 mg/kg
- All spice samples within limits
Cadmium — herbs (n=163):
- Range: <LOQ (0.020) to 2.170 mg/kg DM
- 24 samples (15%) exceeded WHO 0.3 mg/kg limit; exceedances found in 9 species: hoary rockrose, heath speedwell, yellow bedstraw, southernwood, marshmallow root, globe artichoke leaves, red raspberry leaves, hollyhock flowers, midland hawthorn fruit
- Highest Cd: hoary rockrose (max 2.17), common mugwort (max 1.67), globe artichoke (mean 0.603), hollyhock (mean 0.465), heath speedwell (mean 0.453)
Cadmium — spices (n=61):
- Range: <LOQ (0.020) to 0.082 mg/kg — no exceedances
- Highest Cd: cumin (mean 0.072 mg/kg), black pepper (max 0.080 mg/kg)
- Basil, turmeric, allspice, fennel, cloves: Cd below LOQ in all samples
Arsenic — spices: Black pepper contained detectable As in some samples (range <LOQ to 0.863 mg/kg, mean 0.053 mg/kg); peppers also had As (<LOQ to 0.178 mg/kg); other spices were below LOQ (0.1 mg/kg). Note: reported as total As (tAs), not speciated.
Mercury: Range across all categories: <LOQ (0.005) to 0.030 mg/kg DM. Only field horsetail had notable Hg at mean 0.015 mg/kg. Most samples were at or below LOQ. Commercial spices and herbs essentially uniformly below LOQ (consistent with Fischer & Brodziak-Dopierała 2022 findings).
Tea (green China, n=8):
- Cd: 0.069–0.098 mg/kg (mean 0.034)
- Pb: <LOQ to 0.150 mg/kg (mean 0.070)
- As: <LOQ (all below 0.1)
- Hg: <LOQ to 0.007 mg/kg (mean 0.006)
Coffee (roasted Arabica, n=8):
- Cd: <LOQ to 0.088 mg/kg (mean 0.058)
- Pb: 0.021–0.791 mg/kg (mean 0.140) — note one high value (0.791)
- As: <LOQ
- Hg: <LOQ to 0.007
Risk assessment at Polish consumption rates (0.7 g/day herbs, 0.7 g/day spices, 2.7 g/day tea, 7.8 g/day coffee):
- TTHQmax: spices ≤ 4.23×10⁻², herbs ≤ 2.51×10⁻¹, China tea ≤ 4.03×10⁻², Arabica coffee ≤ 1.25×10⁻¹
- All TTHQmax values < 1 (no noncarcinogenic health risk)
- Carcinogenic risk from As (maximum value) = 1.29×10⁻⁵ — below USEPA acceptable maximum of 1×10⁻⁴
Methods (brief)
ICP-MS (Varian 820-MS) for Pb, Cd, As; mercury analyzer AMA 254 for Hg. Microwave mineralisation with 65% HNO3 (10 mL, stepwise at 400W/363K, 800W/393K, 1600W/483K). Validation: recovery 90–101% for all analytes; reference materials INCT-TL-1 (tea leaves) and INCT-MPH-2 (mixed Polish herbs). Results expressed as mg/kg DM with moisture-content correction. As is reported as total As (tAs); the study does not speciate iAs from organic As — all As values should be interpreted accordingly. Samples collected 2015–2018 from farms in eastern Poland and supermarkets in Lublin.
Implications
Certification: This is the reference study cited by both Fischer 2022 and Winiarska-Mieczan 2023 for Polish herb/spice background context. It provides the most comprehensive Cd, Pb, As, and Hg dataset for Polish culinary herbs, spices, tea, and coffee. The finding that 18% of herb samples exceeded the WHO Pb limit-equivalent when converted to DM is significant for herb supply-chain sourcing specifications. The As data for black pepper (up to 0.863 mg/kg total As in individual samples) is notable; given the EU standard for As in spices is not yet harmonized, and the NYS DOH guidance value for iAs in spices is 0.003 mg/kg, tAs values of this magnitude in black pepper warrant speciation follow-up.
Courses: Comprehensive cross-category comparison (herbs vs. spices vs. tea vs. coffee) from a single study using consistent methodology — a rare and valuable dataset for illustrating how contamination profiles differ by plant part, matrix, and use category.
App: This study provides the primary reference for background Cd, Pb, and tAs ranges in Polish-market herbs, spices, tea, and coffee. The As data for black pepper should be flagged as needing iAs speciation before being used in app risk scoring; the tAs value cannot substitute for iAs in the current model.