Banned pesticides on wild mushrooms and black tea and, above all, the limit value exceeded by up to 100 times! Consumer protectionists and the media sensed a major food scandal. But things turned out quite differently. Udo Pollmer followed the trail of the poison.
by Udo Pollmer / January 26th, 2019
Finally, the cause of dubious residues that has made the tea industry hold its breath for years has been identified. It is about nicotine and anthraquinone contamination. Consumer protectionists naturally...
...denounced illegal practices in the tea plantations, after all, both substances are known pesticides. Nor would it be the first time that illegal spraying of nicotine has caused a scandal. Years ago, a chicken baron illegally obtained tons of the poison from China to rid his flock of bloodsucking mites.
Then nicotine appeared on wild mushrooms. Especially porcini mushrooms from China exceeded the maximum amount umpteen times. The source is still in the dark. Possibly, employees in the collection centres had sprayed a home-made broth made from old cigarette butts against maggots, snails and mosquitoes. Incidentally, this idea, born out of necessity, is also propagated here in well-heeled gardening circles as an ecological alternative.
No sooner had the nicotine residues on the mushrooms dropped back to an inconspicuous level than the poison showed up in the black tea. The limit was 10 µg per kilo - often 100 times that amount was detected. The EFSA had to raise the limit by a factor of 60 to save the tea trade from ruin.
Smoked in the pipe
Some speculated that the pickers smoked a pipe with pleasure, others suspected the tea bush of producing the poison on its own, and still others pointed to pesticides containing nicotine. The organic sector, which thrives on its clean image, reacted with particular irritation: their pickers do not smoke and they do not use pesticides containing nicotine. But then packages of chewing tobacco were sighted in organic tea gardens, hence the residues. But even if the pickers had spat the pulp into the bushes, this would at best explain selective contamination.
Not long ago, the real reason was found. Food chemists in Berlin analysed hundreds of samples: Tea, dust, soil, the hands of the pickers and of course the pesticide mixtures there. Besides nicotine, they also tested for other tobacco alkaloids. Result: The pesticides were innocent, the soil samples clean. There was far too little nicotine on the smokers' hands to explain the exposure.
The decisive clue was that the alkaloids in tea were present in exactly the same proportion as in tobacco. The residues came directly from tobacco plants - they were probably blown away by the wind in the form of dust. The larger the tobacco growing area and the closer the tea plantations, the higher the contamination. In Assam, tobacco cultivation is flourishing; for Darjeeling, the large tobacco growing area in Bihar is relevant. It is only a few 100 kilometres away. The five most important tea-growing countries in the world are also the five largest tobacco producers. This also explains numerous hitherto completely mysterious residue findings on fruit and vegetables.
Caught in the act: the sun
The cotinine content of the tea, however, remained inexplicable at first. Cotinine is usually formed in the human body from nicotine and is excreted in the urine. But this could not be the source. The Berlin colleagues revealed the secret: cotinine also comes from the air. It is formed from nicotine under the influence of sunlight.
This observation also explained the anthraquinone residues in the tea. For years, the substance had caused sleepless nights for the tea trade. The media warned urgently: "Anthraquinone is a substance that is used, among other things, to ward off bird predation after sowing" - a pesticide, in other words, that is "no longer permitted because of the danger to users and consumers". In reality, anthraquinone originated from anthracene - also through oxidation. Anthracene is mainly released in forest fires.
And the moral of the story? The world is not a clean room laboratory. We have to live with that.
Bon appétit!
References
Romanotto A et al: Tabakanbau als Quelle einer Nicotinbelastung indischer Tees. Lebensmittelchemie 2018; 72: 143-145
Köhler A et al: Honeybees and nectar nicotine: Deterrence and reduced survival versus potential health benefits. Journal of Insect Physiology 2012; 58: 286-292
Zechmann S: Nikotin aus Tabak – ein „natürliches“ Mittel gegen Pflanzenschädlinge? CVUA Stuttgart 18. Sept. 2017
Wieland, M et al: Pesticide residues in fresh and dried mushrooms on the German market. CVUA Stuttgart 2010
Ikka T et al: Quantitative validation of nicotine production in tea (Camellia sinensis L.). PLoS ONE 2018; 13: e0195422
Tong B, Speiser B: Rückstände von Anthrachinon in Lebensmitteln. FiBL 20. 2. 2017
BfR: Nikotin in getrockneten Steinpilzen: Ursache der Belastung muss geklärt werden. Stellungnahme 009/2009 vom 28. Februar 2009
Lach G, Bruns S: Pesticides and contaminants in organic products. Vortrag auf der Biofach, Nürnberg 16. Februar 2017
Hantke M et al: Nikotin im Gespräch. MPA Eberswalde. Mpaew.de, ohne Datum
Maurin J: Abwarten und Krebs kriegen. TAZ.de vom 23. 10. 2014
Lippl M: Schwarzer Tee ist mit Pestiziden belastet. Münchener Merkur.de, aktualisiert 23. Januar 2017
Pollmer U: Wie gefährlich ist das Anti-Läusemittel im Frühstücksei? Deutschlandfunk, Mahlzeit vom 04. August 2017
Copyright: EU.L.E. e.V.
Originally published in January 2019: => Dunkle Wolken über schwarzem Tee
English editor: Josef Hueber, Eichstätt
