PCBs are long-lasting pollutants that can remain in the environment decades after their production has ceased. Food is an important route of human exposure, but research has focused largely on animal products, where these compounds can accumulate in fat. Tea plants may also encounter PCBs through their growing environment, and leaves pass through several processing stages before reaching consumers. Yet comprehensive data on PCBs in Chinese commercial tea have been scarce, making it difficult to compare tea varieties, examine geographic patterns or estimate exposure from drinking tea.
A study (DOI: 10.48130/newcontam-0026-0019) published in New Contaminants on 10 July 2026 by Wenfeng Zhou's team, China Agricultural University, reports widespread but generally low-level PCB contamination, differences among tea types and provinces, and a possible contribution from processing.
The team analyzed 192 commercial tea samples produced in 16 Chinese provinces in 2019 and 2020. The collection covered green, black, dark, oolong, white and yellow tea. Using high-resolution gas chromatography and mass spectrometry, the researchers measured 18 PCB compounds: six commonly monitored indicator PCBs and 12 dioxin-like PCBs, whose toxicity can be assessed using toxic equivalency factors. They also compared fresh leaves with processed green tea from the same batch, then estimated intake using measured concentrations, tea consumption figures and an assumed adult body weight of 63 kilograms. PCBs were detected in every commercial sample. The combined concentration of the 18 measured compounds ranged from 9.36 to 4,490 picograms per gram of dry tea. Dark tea had the highest average concentration, at 549 picograms per gram, followed by oolong tea at 241 picograms per gram. Among provinces, Guangdong had the highest average, at 505 picograms per gram, although its estimate was based on four samples. Across the tea categories, the PCB profile was dominated by compounds with three chlorine atoms; CB-28 and CB-52 were particularly prominent. In the matched green tea comparison, the combined PCB concentration rose from 51.2 to 63.7 picograms per gram after processing, mainly because indicator PCB concentrations increased. The change was not statistically significant, so the comparison suggests a possible processing contribution without establishing it as a major source. For the exposure assessment, the researchers converted dioxin-like PCB concentrations into toxicity-weighted values. Green tea produced the highest estimated average weekly intake because it was consumed in the greatest quantity, despite dark tea having a higher average PCB concentration. Estimated intake from each tea category remained well below the health-based benchmark used in the study.
The results offer a starting point for tracking PCB contamination in Chinese tea and examining both environmental and processing-related sources. The risk estimate concerns tea consumption alone; it does not account for PCBs from other foods or exposures. Continued monitoring, particularly of samples with elevated concentrations, could help clarify sources and protect consumers as more evidence becomes available.
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References
DOI
10.48130/newcontam-0026-0019
Original Source URL
https://doi.org/10.48130/newcontam-0026-0019
Funding information
This study was supported by the National Technology Innovation Center for Dairy and Agricultural Science (Grant No. 2024-QNJJ-002) and Technology Innovation Program (Grant No. ASTIP: 1610072025003). The authors declare no conflict of interest.
About New Contaminants
New Contaminants (e-ISSN 3069-7603) is a multidisciplinary platform for communicating advances in fundamental and applied research on emerging contaminants. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of new contaminants research around the world to deliver findings from this rapidly expanding field of science.