de Oliveira et al. 2018 - Metals in traditional and herbal teas

de Oliveira and colleagues measured aluminum, total arsenic, cadmium, total chromium, and lead in 47 traditional and herbal tea products collected in the US market, and then measured the same metals in 5-minute boiling-water infusions. The sample set covered herbal, black, green, and oolong teas with declared origins across 13 countries. The source reports both dry tea-leaf concentrations in mg kg-1 and infusion concentrations in mg L-1 for aluminum or µg L-1 for arsenic, cadmium, chromium, and lead.

Key numbers

• Sample frame: 47 total tea products, including 16 herbal teas, 16 black teas, 11 green teas, and 4 oolong teas collected in the US market.
• Total aluminum in tea leaves: herbal teas ranged 47 to 1745 mg kg-1; traditional teas ranged 50.3 to 2517 mg kg-1. Table 2 reports mean Al 548 ± 111 mg kg-1 for herbal teas, 1655 ± 147 mg kg-1 for black teas, 885 ± 253 mg kg-1 for green teas, 1089 ± 356 mg kg-1 for oolong teas, 1309 ± 135 mg kg-1 for traditional teas overall, and 1050 ± 192 mg kg-1 for all teas.
• Aluminum in 5-minute infusions: herbal tea infusions ranged 0.09 to 3.95 mg L-1; traditional tea infusions ranged 0.02 to 7.51 mg L-1. Table 2 reports mean infusion Al 0.42 ± 0.25 mg L-1 for herbal teas, 4.59 ± 0.47 mg L-1 for black teas, 1.56 ± 0.67 mg L-1 for green teas, 2.58 ± 0.99 mg L-1 for oolong teas, 3.3 ± 0.43 mg L-1 for traditional teas overall, and 2.29 ± 0.62 mg L-1 for all teas.
• Percent aluminum infused after 5 minutes ranged from 0.9 to 49%; Table 2 reports means 6.29 ± 1.84% for herbal teas, 28.2 ± 2.06% for black teas, 14.8 ± 2.75% for green teas, and 19.8 ± 5.72% for oolong teas.
• Total arsenic in leaves: herbal teas had mean 0.26 ± 0.07 mg kg-1; black teas 0.22 ± 0.02 mg kg-1; green teas 0.18 ± 0.07 mg kg-1; oolong teas 0.09 ± 0.01 mg kg-1; all teas 0.21 ± 0.03 mg kg-1. The Results text reports one herbal tea at 1.10 mg kg-1 As, exceeding the WHO 1 mg kg-1 medicinal-plant limit cited by the authors.
• Arsenic in infusions: As was detected above the 0.18 µg L-1 detection limit in 54% of tea infusions and ranged 0.19 to 1.33 µg L-1, below the drinking-water MCL of 10 µg L-1 cited by the authors.
• Cadmium in leaves: Table 3 reports mean Cd 0.19 ± 0.06 mg kg-1 for herbal teas, 0.05 ± 0.01 mg kg-1 for black teas, 0.04 ± 0.01 mg kg-1 for green teas, 0.05 ± 0.01 mg kg-1 for oolong teas, and 0.09 ± 0.15 mg kg-1 for all teas. The Results text reports all tea Cd values from 0.01 to 0.82 mg kg-1, averaging 0.09 mg kg-1, and states that 11% of teas exceeded the 0.3 mg kg-1 WHO herb limit cited by the authors.
• Cadmium in infusions: the Results text reports Cd infusion values 0.13 to 0.61 µg L-1, with 5 to 21% soluble, and below the drinking-water MCL of 5 µg L-1 cited by the authors.
• Total chromium in leaves: Table 3 reports mean Cr 2.32 ± 0.36 mg kg-1 for herbal teas, 7.37 ± 2.04 mg kg-1 for black teas, 1.55 ± 0.42 mg kg-1 for green teas, 0.97 ± 0.29 mg kg-1 for oolong teas, and 3.86 ± 0.83 mg kg-1 for all teas. The abstract reports Cr in 47% of herbal teas and 73% of traditional teas exceeded the Canadian 2 mg kg-1 limit cited by the authors.
• Lead in leaves: Table 3 reports mean Pb 2.37 ± 1.78 mg kg-1 for herbal teas, 0.64 ± 0.11 mg kg-1 for black teas, 0.76 ± 0.12 mg kg-1 for green teas, 0.63 ± 0.21 mg kg-1 for oolong teas, and 1.24 ± 0.56 mg kg-1 for all teas. The abstract reports one herbal tea with 26.4 mg kg-1 Pb, above the WHO 10 mg kg-1 medicinal-plant limit cited by the authors.
• Lead in infusions: the Results text reports soluble Pb from 0.21 to 19.9 µg L-1 after excluding two teas, corresponding to 1.9 to 80% total Pb; the high infusion value was from the same herbal-tea sample that contained 26.4 mg kg-1 Pb in leaves.
• Aluminum intake estimates from tea drinking were reported as 0.001-0.39 mg kg-1 for children and 0.003-0.56 mg kg-1 for adults, below the provisional tolerable weekly intake for Al of 1.0 mg kg-1 cited by the authors.

Methods (brief)

Tea samples were dried at 65 °C to constant weight, ground, and digested as approximately 0.5 g portions with HNO3/H2O2 using USEPA Method 3050B on a hot block. Infusions were prepared by adding 50 mL boiling double-DI water to 0.5 g tea leaves, mixing, covering, boiling for 5 min, filtering through Whatman No. 40 filter paper, cooling, and diluting to 50 mL. Al, As, Cd, Cr, and Pb were analyzed by ICP-MS. NIST Tomato Leaves SRM1573a was analyzed with each batch; reported CRM results were Al 560 ± 11, As 0.110 ± 0.003, Cd 1.59 ± 0.005, and Cr 1.86 ± 0.110 µg g-1, compared with certified values Al 598 ± 12, As 0.112 ± 0.004, Cd 1.52 ± 0.04, and Cr 1.99 ± 0.06 µg g-1. The paper reports total As and total Cr only; it does not speciate inorganic arsenic or hexavalent chromium.

Implications

Certification (HMTc): This paper contributes direct occurrence evidence for true-tea-camellia-sinensis and herbal-botanical-infusions, with separate dry-leaf and infusion units. The chromium and aluminum findings are the strongest signals in traditional teas; the high herbal-tea lead and arsenic values are category-level flags but should not be treated as brand-ranked values.

Courses: The source is useful for teaching why tea evidence needs both dry-product and infusion matrices, and why tAs/Cr measurements cannot be re-labelled as iAs or Cr(VI).

App: The source can support tea, camellia-sinensis, and herbal-botanicals contamination-profile context for Al, tAs, Cd, Cr, and Pb, with a US-market sampling frame and mixed declared product origins.

Wiki pages this source may touch

• aluminum
• arsenic-total
• cadmium
• chromium
• lead
• tea
• camellia-sinensis
• herbal-botanicals
• true-tea-camellia-sinensis
• herbal-botanical-infusions
• tea
• tea-infusions

Verification notes

• PDF text was extracted with pdftotext -layout to /tmp/mfk_june8_567.txt; the abstract, Sections 2.1-2.4, Results text, Table 1, Table 2, Table 3, and Conclusion were checked against this page.
• DOI 10.1016/j.scitotenv.2018.03.215, raw handle MFK_metal-concentrations-in-traditional-and-herbal-teas, and cite-key path wiki/sources/deoliveira2018-traditional-herbal-teas-metals.md were checked before creation; no existing source page was found.
• Units are copied as printed: dry tea values in mg kg-1, Al infusion values in mg L-1, and As/Cd/Cr/Pb infusion values in µg L-1. No conversions were performed.
• Speciation: As is total arsenic and Cr is total chromium. The page does not promote tAs to iAs or Cr to Cr(VI).
• Brand firewall: Table 1-3 name individual tea brands/products. This page reports tea-type and category-level values only and omits brand names.
• Frontmatter slugs were checked against docs/gpt-collaboration/taxonomy-snapshot.md; herbal-tea and tea-infusion are matrix descriptors rather than product or ingredient slugs.

Page history

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