How much PCB exposure comes from drinking tea? Researchers found detectable PCBs across major Chinese tea varieties, but estimated exposure remained well below health-based safety thresholds.
Tea is a daily drink for millions, but the leaves can absorb persistent pollutants from the environment and during cultivation and processing. A nationwide study has now examined the presence of polychlorinated biphenyls (PCBs) in commercially produced tea across China. (1✔ ✔Trusted Source
Profiling of polychlorinated biphenyls in Chinese tea: national distribution, variety-specific variations, and the impact of processing
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What Did Researchers Find About PCBs in Chinese Tea?
Researchers tested 192 tea samples collected from 16 provinces and covering all six major types of Chinese tea. The analysis looked for 18 PCB compounds, including six indicator PCBs and 12 dioxin-like variants. PCBs were detected in every sample tested. However, the researchers’ health risk assessment found that exposure through Chinese tea consumption is currently unlikely to pose a significant health risk to consumers.
“Tea leaves have a long journey from the field to the cup, and contaminants can potentially enter at several stages,” said corresponding author Wenfeng Zhou. “Our study provides a national baseline that helps us understand where PCBs occur in tea, how processing may influence their levels, and what those concentrations mean for consumers.”
The total concentration of the 18 PCBs ranged from 9.36 to 4,490 picograms per gram of dry tea. Among the six tea categories, dark tea had the highest average concentration at 549 pg/g, followed by oolong tea at 241 pg/g. Yellow tea had the lowest average level at 93.3 pg/g.
Where Were PCB Levels Highest in Chinese Tea?
Geographic differences were also evident. Tea produced in Guangdong had the highest average PCB concentration at 505 pg/g, followed by Yunnan, Chongqing, Guangxi and Shaanxi. The researchers suggest that these differences may reflect a combination of local environmental contamination, historical industrial activity and differences in tea production methods.
The chemical fingerprints of the contaminants offered additional clues. Lower-chlorinated PCBs were dominant, particularly trichlorobiphenyls. Two compounds, CB-28 and CB-52, contributed strongly to the overall PCB profile, and similar contamination patterns appeared across most tea-producing regions.
To investigate whether manufacturing itself could contribute to PCB levels, the researchers compared fresh green tea leaves with tea produced from the same batch. Total PCB concentrations increased from 51.2 to 63.7 pg/g after processing, largely because indicator PCBs increased. However, the difference was not statistically significant, indicating that processing was not a major source of PCB contamination in this experiment.
Does Drinking Tea Pose a PCB Health Risk?
For consumers, the most reassuring result came from the health risk assessment. The researchers calculated PCB exposure using World Health Organization toxic equivalency factors and typical tea consumption rates. Even green tea, which produced the highest estimated weekly intake because it is consumed in larger quantities, remained far below established tolerable intake thresholds.
The authors caution that the assessment covers PCB exposure from tea alone and does not represent total exposure from an individual’s entire diet. Because PCBs persist in the environment and can accumulate through food chains, continued monitoring remains important.
The study establishes a national baseline for PCBs in Chinese commercial tea and identifies both geographic location and processing as factors worth monitoring. The findings may help guide future food safety surveillance and support efforts to reduce contaminant entry throughout the tea production chain.
References:
- Profiling of polychlorinated biphenyls in Chinese tea: national distribution, variety-specific variations, and the impact of processing – (https://www.maxapress.com/article/doi/10.48130/newcontam-0026-0019)
Source-Eurekalert