Smoked tea is a very typical tea due to the barbecue smell of the leaves and the atypical taste of the liquor reminiscent of whisky. Unfortunately for tea lovers, more and more French tea shops are banning certain smoked teas because they are considered potentially carcinogenic. If one is interested in scientific studies, is this really the case?
Smoked tea is very popular in Europe. The best known smoked tea is made from Lapsang Souchong, a black tea that grows in the mountainous (Wuyi) regions of Fujian in China. After oxidation, the leaves of Lapsang souchong are arranged in bamboo racks that rest on a grid. Below the grid, pine wood is burned, the combustion fumes will be absorbed by the tea leaves until the leaves are dry. The special smoky taste of this type of tea comes from the terpenoids, organic compounds that leave a spicy taste in the mouth and the pyrolysis of the original compounds.
Why have some European tea stores withdrawn some smoked teas from the market?
Our food is regularly monitored by various European health authorities, including the European Food Safety Authority. These agencies provide health recommendations on food to the European Commission, which then drafts the standards that food must meet. But there are also internal agencies in each country. This is where the cup of smoked tea has not gone since France (and to some extent Germany) have largely tightened the standards for smoked tea set by the European Commission in 2015, making smoked teas unsaleable on the market.
The culprits? Polycyclic aromatic hydrocarbons (PAHs). More specifically, four molecules belonging to this family are targeted (PAH4): benzo(a)anthracene, chrysene, benzo(b)fluoranthene and benzo(a)pyrene. PAH4 are volatile molecules that can be derived from pyrolytic reactions, for example by burning wood or during cooking. In the case of smoked tea, these PAH4 attach to the surface of the tea leaves when the wood is burned.
The problem of PAH4 is well known to health authorities because they are toxic, carcinogenic substances. In a recent scientific review, Moorthy and his collaborators summarized the mechanism of action of PAHs and the health consequences. These molecules are called lipophilic, meaning that they are not soluble in water but can cross the cell membrane which is composed of lipids. The cell has molecules capable of degrading PAHs: these are cytochromes (CYP1A1/B1).
However, PAH degradation produces molecules that form adducts with a strong affinity for DNA. This can induce an accumulation of gene mutations in the cell and can lead to "making" the cell "cancerous". There are many studies that demonstrate the involvement of PAHs in the development of lung cancer.
What is known about PAHs(4) in smoked tea?
Several health agency reports and scientific studies are available on the subject. All agree that PAH4 levels are high in smoked tea leaves and may exceed current standards. However, the reality is much more complex than that.
If we take the results obtained in 2013 for PAH contamination of foodstuffs on French soil as well as the report issued in 2018 by the agencies ETC and EHIA (now Tea & Herbal Infusions Europe), it would appear that the levels of PAH4 in smoked tea leaves are 10 to 100 times lower than products consumed massively cooked meats and that the water of the tea infusion would contain little PAH (5%) because PAH are mostly insoluble in water.
If only few PAHs are found in the infusion, then what is the problem?
The problem with standards is that they are based on legal thresholds that also take into account socio-economic and political factors. When considering a carcinogenic substance, one must also take into account the threshold based on risk (toxicological data based on human consumption) and the threshold based on toxicology (threshold for which the molecule causes real toxicity in X% of cases).
If there is a lack of hindsight on the actual toxicology and risk data, the legal thresholds may be under- or overestimated since it is not known exactly how many people can develop a tumor or even cancer. Recently, Lee and colleagues conducted a study to determine the risk of PAH4 in smoked tea based on known risk thresholds. They concluded that PAH4s in tea infusions present a low public health risk, but they lack data to be able to say whether they underestimate or overestimate the risk. Because there is currently no monitoring of smoked tea consumption in relation to the occurrence of cancer!
Moreover, in a study by Pincemaille et al. others found that PAHs in smoked tea diffuse faster in water than other foods and that the nature of the molecules diffused in water is dependent on the smoked tea leaves. This may explain the refocusing of smoked tea manufacturing practices since woods other than spruce are preferred for combustion (less PAH4 released , etc).
It is also important to note that other PAHs are not evaluated in tea leaves, such as PAHs8. Therefore, it cannot be excluded that further controls may be needed later on to ensure the safety of smoked teas.
Compared to the various studies and reports issued by health agencies, smoked tea would not present health hazards of concern. Infused smoked tea leaves would contain less Polycyclic Aromatic Hydrocarbons than your grills! This does not mean that the danger is nil, since only part of the PAHs are measured and there is a lack of hindsight on the actual risk and toxicological thresholds.
This is just another nanny state bull*hit of european countries, where anything that could be construed as "unhealthy" gets banned.
My husband and I have drunk lapsing souchon tea daily since the 1980's. Averaging 6 x 400ml cups daily. We buy 2 kilo's of the tea about every 8 weeks.
For us it would mean a big step to find a replacement type of tasting tea that satisfies us if it ever should come to a definite ban on imports. I am very interested in the ongoing studies into this subject and would appreciate being kept informed of developments.
Thank you for writing the above,