Grzadka et al. 2024 - Radioisotopes and heavy metals in commercial teas

Grzadka and colleagues measured radionuclides and elemental contaminants in 30 commercial true-tea samples imported to the Polish market. The source is routeable for tea and tea-infusion occurrence evidence because it reports dry-leaf metal concentrations, post-brewing residues, leaching behavior, and non-carcinogenic hazard quotients for black, green, red, oolong, and white teas. Lead, cadmium, and vanadium were below the reported MIP-OES detection limits in the result narrative, while chromium, aluminum, manganese, nickel, copper, molybdenum, iron, and phosphorus varied by tea type and origin.

Key numbers

All metal concentrations below are in mg/kg dry tea material unless otherwise stated. Radionuclides were reported in Bq/kg dry weight.

Sample set and preparation

The study tested 30 tea samples sold on the Polish market during 2021-2023. The sample set included 16 black teas, 7 green teas, 2 red teas, 2 oolong teas, and 3 white teas. Brewing used 20 g tea per 1 L redistilled water. Black tea was brewed at 100 degrees C; pu-erh/red and oolong teas at 85-90 degrees C; green tea at 75 degrees C. Black, green, red, and oolong teas were brewed for 3 minutes; white tea was brewed for 5 minutes. The authors analyzed tea leaves before and after brewing, not the separated infusion liquid directly.

MIP-OES detection limits

Table 3 reports these limits of detection: Al 1.500, Cd 0.051, Co 0.100, Cr 0.016, Cu 0.025, Fe 2.837, Mo 0.022, Mn 0.600, Ni 1.100, P 11.000, Pb 0.240, and V 0.020 mg/kg.

The result narrative states that Pb, Cd, and V were below LOD in all samples and were therefore not plotted for concentration comparison. The THQ section later says the lead concentration was included as the LOD value for almost all samples, so this page treats Pb as non-detect/LOD-substituted risk input rather than a quantified occurrence range.

Metals in dry tea leaves

Reported text ranges by tea class:

Phosphorus was also measured as a plant nutrient rather than a heavy-metal contaminant: black teas 1000-2800 mg/kg, green teas 1100-2900 mg/kg, red teas 2000-2900 mg/kg, oolong teas 1500-2900 mg/kg, and white teas 2500-4000 mg/kg.

Radionuclide context

For Sri Lankan black teas, the paper reports the activity order as 40K > 210Pb > 226Ra > 228Th > 137Cs. In that subset, 40K ranged from 976 +/- 134 to 1100 +/- 48 Bq/kg before brewing and from 638 +/- 135 to 934 +/- 45 Bq/kg after brewing. 137Cs ranged from 2.1 +/- 0.9 to 4.1 +/- 1.3 Bq/kg before brewing and from 1.5 +/- 0.4 to 2.8 +/- 0.6 Bq/kg after brewing; the paper notes the international radionuclide action level for food as 100 Bq/kg. 226Ra did not exceed 7.0 Bq/kg in the Sri Lankan black-tea subset, and post-brewing leaf residues corresponded to 10-43% release into infusion.

Risk assessment

The consumption-risk calculation used 11.4 g/day tea intake, 365 exposure days/year, 57 exposure years, and 61.75 kg body weight. Table 4 reports HQ values for Cr, Cu, Mo, Pb, Mn, and Ni and total THQ for all 30 samples. No sample exceeded the THQ threshold of 1. The highest THQ in the table was 0.6273 for the Iranian-origin black tea sample BIr1; the Results text also describes Brazilian green tea GB1 as the highest at 0.6329, but the printed table gives GB1 as 0.6133. White and green teas had the highest average THQ values reported in text, 0.4599 and 0.4327, respectively. Mn dominated THQ uncertainty.

Methods (brief)

Radionuclides (40K, 137Cs, 226Ra, 210Pb, and 228Th) were measured by gamma spectrometry using a Canberra HPGe detector after the samples were sealed and held for 30 days to allow equilibrium between radon and progeny. For elemental analysis, 1 g of tea was microwave-digested in nitric acid, diluted to 10 mL, and measured by Agilent MP-AES 4210 MIP-OES with four repetitions and automatic background correction. The paper reports wavelengths and LODs for Al, Cd, Co, Cr, Cu, Fe, Mo, Mn, Ni, P, Pb, and V.

Implications

Certification: This is Polish-market/imported-product tea evidence, not a US-market benchmark pool input without jurisdictional stratification. It is useful for true-tea dry-leaf occurrence and brewing-transfer context, especially for Al, Mn, Ni, Cr, Pb non-detect handling, and Cd non-detect handling.

App: Route to tea, true tea, tea infusions, and the metals pages for lead, cadmium, chromium, nickel, manganese, aluminum, copper, molybdenum, and iron. Do not route as herbal tea, supplement tea, kombucha, or infant beverage evidence.

Courses: Useful for teaching dry-leaf versus brewed-residue basis, LOD substitution in hazard quotients, and why brand-level names are not needed for category-level occurrence evidence.

Wiki pages this source may touch

• tea
• camellia-sinensis
• tea
• true-tea-camellia-sinensis
• tea-infusions
• lead
• cadmium
• chromium
• nickel
• aluminum
• copper
• iron
• manganese
• molybdenum
• index

Verification notes

The source identifies samples by generic tea type, origin, and acronym, not brand names; this page therefore preserves category-level origin/sample labels only. The main-text concentration figures are not extractable as a complete numeric per-sample table from the PDF text, so this page records the printed narrative ranges and the exact Table 3 LODs and Table 4 THQ values rather than estimating graph coordinates. The paper contains a small internal inconsistency: the Results text says Pb was below LOD in all samples, while the THQ section says Pb was substituted at the LOD for almost all samples; this page treats Pb as non-detect/LOD-substituted unless a later supplemental data file provides exact measured values.

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.