Li et al. 2015 — Aluminum and heavy metals in Jiangxi green tea leaves and infusions
This study measured Al, Cd, Co, Cr, Cu, Ni, and Pb in 26 commercially available green tea samples from four locations in Jiangxi Province, China (Sanqingshan County, Wuyuan County, Jinggangshan City, and Lushan County), analyzing both dry tea leaves and sequential tea infusions (first through fourth), using ICP-MS and ICP-AES. Average metal contents in tea leaves (dry weight) were: Al 487.57, Cd 0.055, Co 0.29, Cr 1.63, Cu 17.04, Ni 7.71, Pb 0.92 mg/kg. Target hazard quotients (THQ) from 2.33×10⁻⁵ to 1.47×10⁻¹ and hazard index (HI) from 1.41×10⁻² to 3.45×10⁻¹ in tea infusions were all less than 1, indicating no significant noncarcinogenic health risk from tea consumption under conventional Chinese drinking habits (multiple sequential infusions). Cu content in one sample exceeded China’s maximum allowable level for tea (NY 288-2012).
Key numbers
Tea leaf concentrations (mg/kg dry weight), Table 1:
| Element | Mean ± SD | Range | China threshold |
|---|---|---|---|
| Al | 487.57 ± 234.46 | 227.41–911.67 | N/A |
| Cd | 0.055 ± 0.020 | 0.025–0.11 | 1 mg/kg |
| Co | 0.29 ± 0.13 | 0.11–0.58 | N/A |
| Cr | 1.63 ± 0.67 | 0.28–1.63 | 5 mg/kg |
| Cu | 17.04 ± 4.69 | 8.42–31.48 | 30 mg/kg |
| Ni | 7.71 ± 2.91 | 2.71–13.57 | N/A |
| Pb | 0.92 ± 0.42 | 0.12–2.24 | 5 mg/kg |
All Cd, Cr, and Pb values below China national standards for tea. Cu exceeded maximum allowable level in 1 of 26 samples (3.85% exceedance rate). Al is the most abundant element (Al accumulator).
Infusion behavior: Pb, Cd, Cu, and Al mainly remained in tea leaves rather than transferring to infusion. Metal concentrations in infusion decreased with increasing infusion number. Maximum allowable levels for tea infusions vs drinking water (mg/L): Al 0.2, Cd 0.005, Cr(VI) 0.05, Cu 1.0, Ni 0.02, Pb 0.01. All infusion concentrations were below drinking water limits.
LOD values: Pb 2.0×10⁻², Cd 1.0×10⁻², Cu 3.0×10⁻², Cr 8.0×10⁻², Co 1.0×10⁻², Ni 2.0×10⁻² µg/L; Al (ICP-MS) 0.32 µg/L, Al (ICP-AES) 4.0 µg/L. Recovery ratios 95.0–104.5%.
Methods (brief)
ICP-MS (ELAN 6000, PerkinElmer-Sciex) for Cd, Cr, Cu, Ni, Pb and Co in tea leaves and infusions; ICP-AES (Ultima 2, HORIBA Jobin Yvon S.A.S.) for Al in tea leaves. Tea leaves ground through 0.5 mm polyethylene sieve, dry-ashed at 510°C for 3.5 h, dissolved in concentrated HNO₃ plus 0.5 mL H₂O₂. Tea infusion experiment: 1 g dry tea in 100 mL boiling ultrapure water, 15 min infusion time, conducted in triplicate. Health risk assessed using THQ (target hazard quotient) and HI (hazard index) per US EPA framework. Chinese adult body weight assumption: 60 kg; daily tea infusion intake assumption: 1250 mL/person/day, corresponding to 8.0 g dry tea/person/day.
Limitations
n=26 from a single province (Jiangxi); not nationally representative of Chinese green tea. Does not include As, Hg, or Sn. Health risk assessment assumes the RfD for Cr is that of Cr(III), not Cr(VI), because acidic stomach conditions can reduce Cr(VI) to Cr(III). The study examines commercially available tea from Jiangxi markets; production-region variability within Jiangxi is not fully characterized. First-infusion higher metal concentrations support the authors’ recommendation to discard the first brew.
Implications
- Certification: Al (mean 487.57 mg/kg dry weight in leaves) is an important accumulator element in tea. Pb (mean 0.92 mg/kg dry weight) is below China’s 5 mg/kg leaf standard but relevant for dietary exposure via high-consumption patterns. Cd (mean 0.055 mg/kg dry weight) is low relative to China’s 1 mg/kg threshold.
- Courses: Provides well-controlled comparison of tea-leaf versus tea-infusion metal concentrations, demonstrating that most Pb, Cd, and Al remain in the leaf rather than transferring to the infusion — directly applicable to understanding bioaccessibility vs total metal content in tea.
- App: Note only — contamination_profile for tea should distinguish dry-leaf basis from infusion basis. This source reports leaf dry weight; infusion values are substantially lower.
- Microbiome: Not applicable as primary topic.