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Occurrence, exposure and health risk assessment of heavy metals in green tea samples cultivated in Hangzhou area

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Overview

This study is the most analytically comprehensive recent survey of heavy metals in Hangzhou-area green tea, measuring 15 elements (Al, arsenic (As), Ba, cadmium (Cd), chromium (Cr), Cu, mercury (Hg), Li, Mn, nickel (Ni), lead (Pb), Sb, Se, tin (Sn), V) in 120 tea samples by ICP-MS. All 120 samples were below Chinese standard limit values for As, Cd, Cr, Hg (NY659-2003 agricultural industry standard for tea) and Pb (GB2762-2022 national food safety standard). The comprehensive pollution index (P = 0.094) and all single-factor pollution indices were well below 0.7, placing Hangzhou-origin tea in the “safe/clean” classification. Health risk assessment yielded a cumulative hazard index (HI) of 0.42, with Mn the dominant contributor (HQ = 0.40); the study concludes that green tea consumption from this region poses no meaningful health risk.

Key numbers

All concentrations in tea leaves (mg/kg dry weight, Table 4):

  • aluminum (Al): range 126.00–975.00, mean 276.50 ± 148.50, median 227.00 (detection 100%)
  • As: range 0.013–0.17, mean 0.054 ± 0.030, median 0.047 (detection 100%)
  • Ba: range 4.01–103.00, mean 21.40 ± 15.92, median 16.75 (detection 100%)
  • Cd: range 0.0093–0.17, mean 0.040 ± 0.024, median 0.034 (detection 100%)
  • Cr: range 0.044–3.52, mean 0.62 ± 0.55, median 0.42 (detection 100%); total Cr, no hexavalent chromium (Cr-VI) speciation
  • Cu: range 7.48–31.00, mean 13.80 ± 3.68, median 13.25 (detection 100%)
  • Hg: range ND–0.017, mean 0.0033 ± 0.0034, median 0.0028 (detection 69.2%); total Hg, no methylmercury (MeHg) speciation
  • Li: range 0.025–1.02, mean 0.18 ± 0.15, median 0.15 (detection 100%)
  • Mn: range 202.00–2010.00, mean 836.00 ± 274.76, median 814.50 (detection 100%); highest-mass element measured
  • Ni: range 2.03–29.90, mean 10.70 ± 4.37, median 10.35 (detection 100%)
  • Pb: range 0.051–1.71, mean 0.45 ± 0.30, median 0.37 (detection 100%)
  • Sb: range ND–0.22, mean 0.022 ± 0.022, median 0.018 (detection 98.3%)
  • Se: range ND–0.18, mean 0.076 ± 0.040, median 0.076 (detection 93.3%)
  • Sn: range ND–12.80, mean 0.18 ± 1.22, median 0.022 (detection 94.2%)
  • V: range 0.016–0.71, mean 0.11 ± 0.11, median 0.083 (detection 100%)

Chinese regulatory limits applied (Table 2, mg/kg dry leaf):

  • NY659-2003 (agricultural industry standard for tea): As 2.0, Cd 1.0, Cr 5.0, Hg 0.3
  • GB2762-2022 (national food safety standard): Pb 5.0

Comprehensive pollution index (Table 6): Pi single-factor — As 0.027, Cd 0.040, Cr 0.12, Hg 0.011, Pb 0.090; P comprehensive = 0.094 (all far below 0.7 “safe/clean” threshold).

Estimated daily intake and hazard quotient (Table 7; tea ingestion rate 3.6 g/person/day, body weight 64.36 kg, exposure duration 77.4 years):

  • Al: EDI 3.13 µg/kg-bw/day, HQ 0.0031
  • As: EDI 0.00061, HQ 0.0020
  • Ba: EDI 0.24, HQ 0.0012
  • Cd: EDI 0.00045, HQ 0.00025
  • Cr: EDI 0.0070, HQ 4.7×10⁻⁶
  • Cu: EDI 0.16, HQ 0.0039
  • Hg: EDI 0.000037, HQ 0.00012
  • Li: EDI 0.0020, HQ 0.0010
  • Mn: EDI 9.48, HQ 0.40
  • Ni: EDI 0.12, HQ 0.0061
  • Pb: EDI 0.0051, HQ 0.0014
  • Sb: EDI 0.00025, HQ 0.00062
  • Se: EDI 0.00086, HQ 0.00017
  • Sn: EDI 0.0020, HQ 3.4×10⁻⁶
  • V: EDI 0.0012, HQ 0.00018
  • Cumulative HI = 0.42 (Mn contributes 95% of HI)

Methods (brief)

Inductively coupled plasma mass spectrometry (Agilent 8900 ICP-MS) with microwave digestion (CEM, USA). Sample mass 0.3 g tea leaves digested with 5 mL HNO₃ (two-stage program: 140°C 2 min hold, then 180°C 30 min hold); digestate diluted to 25 mL with ultrapure water. Internal standard: indium (In) 3 µg/L. Monitored isotopes: ⁷Li, ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, ⁶⁰Ni, ⁶³Cu, ⁷⁵As, ⁷⁸Se, ¹¹¹Cd, ¹¹⁸Sn, ¹²¹Sb, ¹³⁷Ba, ²⁰²Hg, ²⁰⁶ᐟ²⁰⁷ᐟ²⁰⁸Pb. Calibration r > 0.9995–0.9999; LODs 0.0003–0.03 mg/kg. Method validated against standard reference material GBW10052 (GSS-30 green tea biocomposition); recoveries 86.4–97.5%. Method validation followed European Commission SANCO/3103/2000 guidelines. ND values handled per WHO: substitution depends on proportion of below-LOD results (0 if <80% below LOD, LOD if 60–80% below LOD; middle-bound = LOD/2). Samples collected from supermarkets (67 of 120), local markets (43 of 120), and planting sites (10 of 120) across seven Hangzhou-area districts: Xihu (33), Yuhang (26), Fuyang (18), Linan (13), Chunan (12), Jiande (9), Tonglu (9).

Limitations

Geographic scope limited to Hangzhou area — cannot be generalised to all Chinese green tea. Market samples dominate (supermarket + local market = 110 of 120); origin-labelling reliability not assessed. Total Cr reported; Cr-VI not speciated. Total Hg reported; MeHg not speciated (acceptable for tea leaves where inorganic Hg dominates, but limits direct comparison to seafood Hg literature). Mn contributes 95% of the HI but Mn is generally not considered a regulatory concern in tea at these concentrations. No leaching/infusion data — all values are dry-leaf concentrations; as-consumed exposure depends on leaching fractions reported elsewhere. Tea ingestion rate (3.6 g/person/day) is a Zhejiang Province average and may understate exposure for heavy tea-drinking sub-populations.

Implications

  • Certification: Hangzhou-origin green tea (Longjing/Dragonwell production region) is clean by Chinese standards and by health-risk metrics. Mean Pb 0.45 mg/kg and mean Cd 0.040 mg/kg (dry leaf) are well within NY659-2003/GB2762-2022 limits. Al at mean 276 mg/kg (dry leaf) is the highest non-Mn metal by mass and is relevant for any HMT&C product category that includes Al-bearing tea ingredients.
  • Synthesis input: provides a 120-sample baseline for green tea at a recognised premium origin (Hangzhou/West Lake). Contributes occurrence data to Camellia sinensis for total arsenic (tAs), Cd, Cr-total, Pb, total mercury (tHg), Al, Ni, Cu, Mn, plus the longer-tail elements Ba, Li, Sb, Se, Sn, V.
  • App: dry-leaf basis values; conversion to as-consumed (infusion) requires leaching fractions from companion sources (e.g., Brzezicha-Cirocka 2016 reports ~30–45% leaching for Pb, ~10–44% for Cd in green tea infusions). Flag for synthesis pass on tea.

Update history

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