Öztürk et al. 2024 — Aluminium in black, green, and white tea infusions: teapot material and infusion time effects
This study measured Al concentrations in infusions of black, green, and white tea brewed in five teapot materials (aluminium, copper, glass, steel, porcelain) at three infusion times (5, 10, 15 min) using HPLC with fluorescence detection, finding Al concentrations ranging from 38.46 ± 5.08 to 845.75 ± 11.14 µg/L across all conditions. Tea type was the dominant determinant of Al concentration: green tea (mean 715.53 ± 97.32 µg/L) reached roughly 14-fold higher infusion Al than black tea (mean 50.36 ± 22.78 µg/L), with white tea intermediate (mean 271.13 ± 48.76 µg/L). Teapot material and infusion time both exerted statistically significant but secondary effects, while hazard quotient calculations indicated that green tea consumption exceeds the JECFA tolerable daily intake of 1 mg Al/kg body weight for all teapot types and infusion times, whereas black tea and most white tea conditions remain below this threshold.
Key numbers
Al concentrations in tea infusions (µg/L; mean ± SD across all teapot types and infusion times):
- Black tea: 50.36 ± 22.78 µg/L (range by individual condition: ~38.5–75.4 µg/L; some aluminium-teapot conditions produced nd at 5 and 10 min)
- Green tea: 715.53 ± 97.32 µg/L (range by individual condition: 573.2–845.75 µg/L)
- White tea: 271.13 ± 48.76 µg/L (range by individual condition: 182–352.7 µg/L)
- Overall range across all conditions: 38.46 ± 5.08 to 845.75 ± 11.14 µg/L
Infusion time effect (means across all teas and teapots):
- 5 min: 339.62 ± 285.12 µg/L
- 10 min: 346.04 ± 291.4 µg/L
- 15 min: 351.36 ± 284.38 µg/L
Teapot material effect (means across all teas and times):
- Aluminium teapot: 287.44 ± 255.98 µg/L
- Copper teapot: 311.07 ± 254.4 µg/L
- Glass teapot: 355.04 ± 280.05 µg/L
- Steel teapot: 387.15 ± 316.67 µg/L
- Porcelain teapot: 387.67 ± 317.53 µg/L
Hazard quotients (HQ; based on 70 kg body weight, 10 g tea/day, JECFA TDI 1 mg Al/kg/day):
- Black tea: HQ < 1 for all teapot types and infusion times (range ~0.11–0.22)
- Green tea: HQ > 1 for all teapot types and infusion times (range 1.64–2.41)
- White tea: HQ < 1 for most conditions; HQ = 1.01 only for 15-min glass teapot infusion
Methods (brief)
HPLC with fluorescence detection (HPLC-FD; Shimadzu prominence series, GL Sciences InertSustain C18 250 × 4.6 mm, 5 µm). Derivatisation with 5-sulfoquinoline-8-ol (HQS) and Bis-Tris buffer; excitation 366 nm, emission 510 nm. Linear range 10–1000 µg/L (r = 0.9983). Tea brewed at 100 °C using 5 g tea in 100 mL ultra-pure water. Analyses in triplicate. Sampling: commercially purchased Turkish tea products. No dry-leaf concentrations reported; all values are infusion concentrations. Note: this method measures total dissolved Al in the infusion, not speciated Al forms.
Implications
Certification: Green tea is a genuine Al exposure concern even when brewed under standard household conditions. At mean 715 µg/L infusion Al, a consumer drinking 300 mL of green tea brewed from 10 g leaves would receive approximately 2.15 mg Al, equivalent to 2.15% of the JECFA TDI for a 70 kg adult — but this calculation assumes only tea as the Al source. Products incorporating green tea extract or matcha at elevated doses amplify this exposure; HMT&C product assessment should account for cumulative Al from all ingredients.
Courses: Strong illustration of why Camellia sinensis is an Al hyperaccumulator and why tea type (leaf processing) matters far more for Al leaching than teapot material or brew time. The 14-fold difference between black tea and green tea infusions at identical brewing conditions is the core teaching point.
App: Infusion Al for green tea ~715 µg/L, white tea ~271 µg/L, black tea ~50 µg/L. These are aqueous infusion concentrations (µg/L), not dry-leaf concentrations (mg/kg); must not be conflated with dry-leaf values from other sources.
Microbiome: Not addressed in this paper.