According to a study published in npj Science of Food, researchers evaluating 60 best-selling online tea samples in China found that all tested varieties met Chinese national safety limits for harmful elements, though conservative risk modeling identified cadmium as the primary contributor to elevated carcinogenic-risk estimates. The investigation highlights complex regulatory gaps between international standards and real-world exposure risks for consumers purchasing tea via e-commerce platforms.
Evaluating Harmful Elements in Online Tea Products
Online retail platforms have changed how consumers purchase everyday goods, including loose-leaf and bagged tea. In 2022, researchers collected 60 online tea samples in China, comprising 10 varieties each of black, white, dark, yellow, oolong, and green tea, classified according to International Organization for Standardization (ISO) 20715 guidelines. Using inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS), the study measured concentrations of six hazardous elements: arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), and lead (Pb). Mean concentrations recorded across all samples were 0.28 mg/kg for arsenic, 0.35 mg/kg for cadmium, 1.18 mg/kg for chromium, 13.2 mg/kg for copper, 0.004 mg/kg for mercury, and 0.65 mg/kg for lead, according to the published data.
None of the maximum concentrations for the six elements exceeded Chinese national safety standards. However, when evaluated against stricter international frameworks, varying compliance levels emerged. Arsenic concentrations remained below Canadian limits across all samples, while 91.7% met or exceeded Iranian thresholds. For cadmium, 65.0% of samples reached or exceeded Canadian limits, and every sample met or exceeded Iranian limits. Furthermore, chromium stayed below Canadian limits in 95.0% of samples, and lead remained universally compliant with Canadian standards while 23.3% of samples exceeded Iranian limits.
Health Risk Modeling and Cadmium Exposure
To understand potential health hazards, the study assessed non-carcinogenic risks using hazard quotients and hazard indexes for youth aged 18 to 44, middle-aged adults aged 45 to 59, and older adults aged 60 and above. According to the findings, the lowest average hazard index appeared in black tea at 0.47, while dark tea recorded the highest at 0.74. Mean hazard index values for young people, middle-aged individuals, and seniors stood at 0.61, 0.59, and 0.62, respectively. Because all hazard index values stayed below 1.0, adverse non-carcinogenic health effects are considered unlikely under the study’s parameters, with arsenic contributing the largest share at 29.0%.
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While modeled carcinogenic risk estimates for youth, middle-aged adults, and elderly groups exceeded the acceptable upper limit of 1.0E-4, the study’s authors noted that the model assumed complete digestion and 100% absorption of elements from dry leaves rather than brewed infusions, likely overestimating real-world risks by more than fourfold.
Carcinogenic risk calculations, structured around United States Environmental Protection Agency (USEPA) protocols, showed values highest in yellow tea at 4.4E-4 and lowest in black tea at 1.5E-4. Green tea registered 3.9E-4, dark tea reached 3.4E-4, white tea hit 2.6E-4, and oolong tea recorded 2.3E-4. Cadmium emerged as the dominant contributor to these modeled carcinogenic risks, accounting for between 77.2% in black tea and 88.4% in yellow tea. Chromium and arsenic contributed average shares of 10.0% and 7.4%, respectively.
Regulatory Standards and Cultivation Challenges
Tea plants frequently grow in acidic soils where hazardous elements naturally occur and accumulate in leaves over time. A national soil survey in China previously identified standard exceedances for arsenic, cadmium, chromium, copper, mercury, and lead, with cadmium displaying the highest exceedance rate among the group. Although pollution indexes under Chinese standards rated all six tea types as safe, Canadian standards indicated light pollution from cadmium in green, yellow, and dark tea, alongside alert levels for oolong and white tea. Iranian standards categorized cadmium and Nemerow synthetic pollution indexes as heavy pollution in green, yellow, and dark teas.
The study’s authors recommended strengthening controls across every stage of the supply chain, encompassing tea cultivation, production, packaging, logistics, and sales, with a specific focus on mitigating arsenic, cadmium, and chromium accumulation. They also emphasized that the health benefits of consuming tea that meets food safety standards often outweigh modeled risks, particularly for black tea, and noted that brewing weaker tea yields lower exposure rates.
Frequently Asked Questions
Did the tested teas violate Chinese safety regulations?
No. According to the research findings, maximum concentrations of all six tested harmful elements—arsenic, cadmium, chromium, copper, mercury, and lead—remained below Chinese national standards across all 60 samples.
Which element contributed most to the modeled health risks?
Arsenic contributed the highest share to non-carcinogenic risk at 29.0%, while cadmium was the dominant contributor to modeled carcinogenic risk, accounting for up to 88.4% in yellow tea.
Why did the study likely overestimate real-world health risks?
The risk assessment model relied on total element concentrations measured in fully digested tea leaves rather than brewed infusions, assuming complete 100% absorption, which the authors noted overestimates actual exposure by more than fourfold.
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