Tea

Completeness scorecard

Deterministic gap audit — no score is composite, no cell is LLM-judged. Each chip is re-derivable by re-running tools/evidence/build-ingredient-scorecard.mjs. review: residuals and missing data are worked autonomously via data/evidence/ingredient-scorecard-review-flags.csv and wiki/completeness-gaps.md.

Tea (Camellia sinensis leaf, processed into green, black, oolong, white, and pu-erh varieties) is the dominant dietary source of aluminum in many populations and a notable source of lead, fluoride (out of scope for this page), and trace heavy metals. The defining biological feature of the tea plant is its aluminum hyperaccumulation: Camellia sinensis tolerates and accumulates aluminum at concentrations of 10,000-100,000 ppb dry weight (orders of magnitude above any other major food-crop leaf), driven by an adaptation to acidic soils where Al is the dominant available cation. The current corpus loads 10 sources spanning China (the largest tea-producing region globally, with the Hu 2023 status assessment covering 4,803 samples nationwide and the Fan 2025 Hangzhou survey at 120 samples), Poland-and-EU import data, Germany (BfR MEAL Study nickel dietary-intake assessment), Ireland (FSAI 2016 total diet study), and broader systematic reviews. The Hu 2023 dataset is the largest single tea heavy-metals dataset in the loaded corpus and provides the strongest distributional anchor for the Pb, Cd, tAs, Cr, tHg, and Cu profile in Chinese-origin product.

Why this commodity accumulates heavy metals

Tea’s heavy-metals profile is shaped by three interacting factors: soil chemistry, the aluminum-hyperaccumulator pathway, and the infusion-extraction question. Soil chemistry: tea is grown predominantly on acidic mountain soils in Yunnan, Anhui, Zhejiang, Fujian (China), Assam and Darjeeling (India), Sri Lanka, Kenya, and similar high-altitude tropical-to-subtropical regions. These soils are naturally elevated in aluminum and frequently in cadmium relative to neutral-pH agricultural soils. Tea bushes take up Al, Cd, and trace metals from the root zone and transport them into leaves; the older the leaf, the higher the metal concentration. The aluminum-hyperaccumulator pathway is the defining feature: green and black teas routinely carry 10,000-100,000 ppb Al dry weight, with pu-erh and aged-leaf product reaching the upper end. The Hardisson 2017 dietary-exposure review documents tea as the dominant aluminum source in many western diets (hardisson2017-aluminium-dietary-exposure-review). The infusion-extraction question is what makes finished-beverage exposure different from dry-leaf exposure: hot water extracts roughly 30-50% of dry-leaf lead, 50-70% of cadmium, 70-90% of fluoride, and a variable fraction of aluminum into the brewed cup. The Jurowski 2023 Polish-market survey (jurowski2023-heavy-metals-green-tea-poland) measured both dry-leaf and infusion concentrations and confirmed the partial-extraction pattern. Atmospheric deposition adds surface Pb to tea leaves harvested in roadside or industrial-corridor settings, particularly relevant for lower-altitude commodity-grade product.

Heavy metal contamination profile

Per-analyte snapshot derived from the machine-readable contamination_profile in the frontmatter above. data gap indicates the literature has been reviewed for this commodity-analyte combination and no usable occurrence data was found (a finding, not a placeholder). The Key sources column shows the top 2-3 contributing sources by year and sample size, with numbered wikilink aliases.

Ranges by source, region, and variety

China is the dominant production-region anchor in the loaded corpus, contributing the Hu 2023 status assessment (n=4,803 samples nationwide, covering green, black, dark, oolong, and white-tea categories) and the Fan 2025 Hangzhou green-tea survey (n=120, 12-metal panel including the rarely-measured Sn and Sb). The Brzezicha-Cirocka 2016 multi-origin comparison sampled 41 green-tea products from Chinese, Indian, Japanese, and other global origins and quantified Cd, Pb, Cr, Ni, Cu, Zn, Co, Mn, Fe variation by origin (brzezicha-cirocka2016-green-tea-geographic-origins). The Jurowski 2023 Polish-market green-tea infusion survey (n=12) is the smallest dataset but contributes both dry-leaf and brewed-infusion measurements and a comprehensive safety assessment (jurowski2023-heavy-metals-green-tea-poland). The Kazeminia 2023 systematic review (n=157 included studies) provides the broadest global synthesis but does not report individual-sample concentrations (kazeminia2023-tea-heavy-metals-review). The BfR 2022 MEAL Study nickel-intake dataset (n=840 across the German diet) identifies tea as a major dietary Ni contributor specifically (bfr2022-nickel-dietary-intake-germany-meal). Within-China spatial variation is substantial: Hu 2023 reports the Pb-and-Cd distribution by province and notes a clustering pattern of elevated values in specific production regions, particularly where tea cultivation has expanded onto historically contaminated soils. Pu-erh (post-fermented dark tea) and other aged-leaf products consistently carry higher Al than fresh-leaf green tea due to the longer leaf-tissue accumulation time.

Processing effects

The processing chain from fresh tea leaf to finished dry product (withering, rolling, oxidation/fermentation for non-green varieties, drying) does not significantly alter the per-mass metal load on a dry-weight basis. Drying removes water and concentrates metals from the fresh-leaf basis to the dry-leaf basis by roughly 4-5×. Post-fermentation aging for pu-erh tea can produce modest additional Al concentration if the storage matrix contributes additional aluminum, though this is not quantified in the loaded corpus. The dominant processing-related question for finished-beverage exposure is the brewing-extraction step: the Jurowski 2023 work and the broader tea-infusion literature establish that hot-water infusion extracts a partial fraction of dry-leaf metals into the cup, with extraction efficiency depending on water temperature, infusion time, water hardness, and leaf surface area. For typical western-style brewing (5-minute infusion, 90-100°C water), Pb extraction is ~30-50% of dry-leaf load, Cd extraction is ~50-70%, and Al extraction is highly variable (10-60% depending on water chemistry and tea form). For Asian-style short-infusion practices (multiple short brews at lower water-to-leaf ratios), extraction per brew is lower but cumulative extraction across multiple brews of the same leaf reaches similar totals. Cold-brew extraction is generally lower than hot-brew. Tea-bag product introduces an additional consideration: the tea-bag material itself can leach trace metals into the brew, though this is small relative to the leaf-derived load.

Ingredient-derivative risk

Loose-leaf dry tea carries the baseline dry-weight metal load. Tea bags carry the same dry-leaf load plus any small contribution from the bag material. Brewed tea (the consumer-facing form) carries the extracted fraction of the dry-leaf load. Matcha (powdered whole-leaf green tea) carries the full dry-leaf load directly to consumption because the consumer ingests the powder rather than infusing and discarding it; matcha is the highest per-serving aluminum exposure form of tea. Tea extracts (used as flavoring in beverages, supplements, baked goods) carry the metal load in proportion to the extraction-to-dry-leaf ratio. Tea-derived ingredients used in cosmetic and topical products are out of scope for this food page. Kombucha brewed on a tea base carries the tea-derived metal load plus any fermentation-vessel contribution; see kombucha-tea-based.

Mitigation options

Sourcing levers

Origin selection is the highest-impact lever for the lead and aluminum profile. The Hu 2023 China-wide assessment identified geographic clusters of higher and lower Pb-and-Cd production regions (hu2023-china-tea-heavy-metals); brand buyers can specify supplier provinces with documented lower metal-load distributions. For aluminum specifically, no growing region is meaningfully lower than another because Al-hyperaccumulation is a species-level feature of Camellia sinensis; the only sourcing lever for Al is to source non-tea herbal infusions for brand positions where Al exposure is the limiting concern.

Agronomic levers

For brand-controlled-supply operations (a small fraction of the global tea trade), soil pH management away from the acid-soil extremes that drive maximum Al-uptake is plausible but not commercially established at scale. Avoidance of phosphate fertilizers with elevated Cd impurity reduces Cd loading; this is a routine recommendation across the tea-agronomy literature.

Processing levers

Choosing younger-leaf product (first-flush, spring-harvest) over older-leaf product (commodity-grade summer-and-autumn harvest) reduces the absolute metal load because younger leaves have accumulated less tissue Al, Pb, and Cd. The trade-off is cost and flavor profile. For finished-beverage operations, brewing-protocol choices (shorter infusion, lower water temperature) reduce extracted Pb but at the cost of flavor strength.

Formulation levers

For tea-blend formulations, dilution with lower-Al herbal infusions (peppermint, chamomile, hibiscus) reduces per-serving Al on a linear-mixing basis. Substituting non-tea botanicals entirely for products targeting low-Al consumers is the formulation-level answer.

Testing and QC levers

Lot-level ICP-MS testing for Pb (detection floor ≤ 100 ppb), Cd (≤ 50 ppb), and Al (≤ 1,000 ppb) is the standard intervention. The Fan 2025 Hangzhou protocol covers 12 metals including the rarely-measured Sn and Sb at appropriate sensitivity (fan2025-hangzhou-green-tea-metals). For tea-bag product, separately characterise the metal contribution of the bag material.

Packaging and storage levers

Standard food-grade packaging does not contribute meaningfully to the dry-leaf metal load. Long-term storage in unsealed bulk does not change the per-mass load. Aging conditions for pu-erh and dark teas use clay-pot or paper-wrapped storage; clay pots with unverified glazes are a potential additional Pb pathway but are not quantified in the loaded corpus.

Regulatory limits that apply

The Codex Alimentarius General Standard CXS 193-1995 does not set tea-specific heavy-metals maxima. The EU Regulation 2023/915 applies general dried-plant-product limits to tea: 2.0 mg/kg Pb maximum (which is generous relative to the typical-range distribution and routinely passed by commercial product) and 0.5 mg/kg Cd maximum. China’s GB 2762-2017 national food-safety standard sets tea-specific Pb at 5.0 mg/kg and Cd at 1.0 mg/kg, looser than EU but applicable to the dominant production region. No regulatory framework currently sets a maximum aluminum level for tea or any other food ingredient, despite the high per-serving Al exposure tea provides; the EFSA 2021 aluminium Q&A (efsa2021-aluminium-food-qa) addresses dietary Al as a category but does not propose tea-specific caps. The Jurowski 2023 Polish-market assessment (jurowski2023-heavy-metals-green-tea-poland) found Pb, Cd, and tAs in green-tea infusions at levels below EU caps for dried-plant product on a dry-weight basis but flagged the cumulative per-serving exposure as worth tracking.

Sources

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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.