Your daily cup of tea may be hiding a toxin

Tea is woven into daily life across Lebanon, offered at breakfast, after meals, between conversations. But a new peer-reviewed study published in Food and Chemical Toxicology raises a quiet concern about the loose tea sitting in kitchen cabinets across Beirut's suburbs: it may contain naturally occurring toxins at levels that exceed internationally recognized safety thresholds, particularly for young children.

The research was led by Dr. Christelle Iskandar, Assistant Professor at the Department of Nutrition and Food Sciences at the American University of Beirut's Faculty of Agricultural and Food Sciences, alongside graduate student Ms. Lynn Abdallah and colleagues from AUB and the Lebanese American University. The team analyzed 32 loose tea samples, both black and green, commonly purchased by Lebanese households, using advanced mass spectrometry techniques to detect a class of plant toxins called pyrrolizidine alkaloids (PAs). The result: PAs were detected in every single sample tested.

What are pyrrolizidine alkaloids?

PAs are naturally occurring compounds produced by weed species that contaminate crops, including tea, during cultivation and harvesting. They are colorless, odorless, and entirely invisible to the consumer. Decades of toxicology research link PAs to liver damage and, with prolonged exposure, increased cancer risk. Children are considered especially vulnerable due to their lower body weight and developing physiology.

The European Union has set maximum permitted levels for PAs in tea, and it is against these benchmarks that the AUB team measured their findings. The results mark one of the first comprehensive investigations into PA contamination in tea anywhere in the Middle East.

What the numbers show

All loose tea samples tested, 100 percent, contained detectable levels of pyrrolizidine alkaloids (PAs). Between 18 and 27 percent exceeded European Union safety limits for adults, including 18 percent of black teas and 27 percent of green teas. More concerning, nearly half of all samples surpassed the stricter safety threshold set for children, which is already half the adult limit. In some cases, PA levels reached up to four times what is considered acceptable for children, raising serious concerns about long-term exposure and consumer safety.

Teas originating from Vietnam and Ceylon were found to carry higher PA concentrations than those sourced from China. Crucially, non-branded loose teas, the kind sold by weight in local markets and grocery shops, showed significantly higher contamination than branded alternatives. For adults, several daily cups would be needed to reach worrying exposure levels. For children, the calculus is entirely different: one cup of a highly contaminated sample could be enough to exceed their tolerable daily intake.

The children's risk

Long-term exposure modeling in the study used a metric called the Margin of Exposure (MOE), a standard tool for evaluating cancer risk over time. For children consuming tea at even moderate levels, the MOE fell below recommended safety thresholds. This does not mean a single cup causes harm, but it does mean that regular consumption of contaminated teas, over months and years, represents a meaningful risk that parents have had no way of knowing about, until now.

A call for action

The researchers are calling on Lebanese authorities to strengthen monitoring of tea imports and local markets, adopt Good Agricultural Practices across the supply chain, and invest in public awareness so that families, especially parents, can make informed choices. For a country where tea is rarely questioned, this study is a quiet but important wake-up call.