Contaminated or Adulterated Tea? It Still Happens

Buying a product—any product, including tea—is based in trust. Trust that the product is what it’s advertised to be. Trust that it’s safe.

So how safe is our tea? Is our trust sometimes misplaced?

Perhaps, but luckily, we have plenty of people who have our backs! And they aren’t just looking out for dangerous contaminants. Turns out that a tea may contain natural ingredients—just not the right ones!

Here’s a look at some ways in which our tea may be compromised, but more importantly, how we’re protected from ever drinking it.

Herbicides, Pesticides, and Heavy Metals

Recently, Taiwan Customs destroyed 287 kg of chamomile from Egypt because the herbicide level was far too high (Strong 3/2/21). The herb was intended for TWG, a high-end tea company.

That may be surprising—we may have thought that upscale companies wouldn’t be subject to this sort of thing because presumably (a) they have the means to buy from highly reputable sources and (b) they have the capability to test the product before selling it to their customers. It also begs the question of whether the producer actually knew the chamomile was contaminated. Or did they know—but either were quite desperate to survive and so took the risk, or else were intentional about the deception.

Chamomile was not the only flagged product. The U.S. Food and Drug Administration (FDA) had issued a list, and chamomile was joined by other possibly problematic teas including fruit tea from Sri Lanka and genmaicha and powdered green tea from Japan (Strong 3/2/21).

As consumers, we, of course, don’t want to ingest high levels of pesticides, herbicides, and heavy metals. We may look for certifications, such as “organic,” which strive to bring accountability and safety to the table. But we also have such agencies as the FDA to thank.

chamomile & gourmet


Chemicals and heavy metals aren’t the only possible hazards lurking in our cup of tea. Recent news articles have alerted us that some tea bags release high levels of microplastic and nanoplastic particles into our tea. With that revelation, companies are working to address these issues or to reassure consumers that their products are safe. (See Dan Bolton’s review of this issue.)

Natural Ingredients (just not the right ones)

Tea can be adulterated by more innocuous substances, although that doesn’t make it ethical. Therefore, researchers are looking for cost-effective and efficient ways to detect such duplicity. 

Last month, a study evaluated the efficacy of using near infrared spectroscopy to analyze green tea that had been mixed with sugar (not by the consumer) or glutinous rice flour (Li et al. 2021).

More concerning to those with tree nut allergies might be this:

Tea . . . is often subjected to adulteration with various undeclared inorganic and plant‐derived materials. Cashew . . .  nut husk is one of the most common plant tea adulterants. (Lagiotis et al. 2020)

Cashew nut husk is a by-product from processing, and is used for cattle food and as a dye. And evidently in tea.

For the past two decades, scientists have been developing ways to molecularly detect the contaminant, in an affordable way, especially as cashew husks continue to be added to tea. In 2017, 14,500 kg of adulterated tea were seized in India, two brands of tea having been mixed with cashew husk (Chauhan). 

Tea can also be stretched with herbal additives—and sometimes tea leaves can be added to herbals.

In one study, scientists evaluated 146 teas and herbals, independently identifying the ingredients by sequencing the DNA and then matching that to existing databases. Did the actual ingredients match the ingredients listed on the tea/herbal packaging?

Of 146 teas, only 58% of them completely matched (Stoeckle et al. 2011).

Of course some may not have matched because the databases were incomplete, differences within a species hadn’t yet been documented, or there simply was an error somewhere, but still!

It’s not great to learn that your tea may be contaminated with different plants (herbals in tea—and actual tea in supposedly no-caffeine herbals!), with weeds, and, disconcertingly, even with non-food plants. Even if the additive is there to improve taste, it shouldn’t be there if it’s not listed in the ingredients.

South Korea Seogwang Sencha


Besides adding something to stretch the tea leaves, additives to enhance perceived quality also exist. Carmine, an artificial coloring, may be added to black tea leaves to make them appear to be of higher quality than they actually are (Wei et al. 2020).

Adding dye to tea has been done for eons. Back when tea was still fairly new in the western world, westerners demanded that green tea be a certain green in color. Chinese producers complied, using gypsum and Prussian blue to color the tea. Lest you think that westerners were innocent “victims,” take a look at this 1874 law case:

adulteration of tea

It makes you wonder how many others were also aware, it being “the trade.” Nothing becomes the “norm” without a lot of willing participants.

In the 1800s, Britain cracked down, and “legislation even punished the adulteration of tea and coffee specifically” (Rappaport 2017:122).

Consumer Protections

Today, there are still:

  • producers that would deceive the buyer
  • agencies that try to prevent adulterated products from entering the market place
  • researchers who work at developing increasingly sophisticated methods to detect adulterants
  • consumers who remain reliant on others to ensure what we buy is what we’ve been told it is, and that it’s safe

Society requires trust in order to function, of course. Today, we have watchdog agencies that help us to maintain such trust.

In the U.S., that includes the Food Safety and Inspection Service, the FDA, and the Centers for Disease Control and Prevention, all of which try to intercept contaminated food and drinks before they ever reach our mouths. When the system works—like when that chamomile was pulled in Taiwan—consumers are protected.

We need to keep our oversight agencies robust, and we should probably buy from trusted sources, to ensure that the only additives in our tea are those that we ourselves added!

Wild Caucasus Mountain

–Chauhan, A., “Cashew nut husk mixed adulterated tea seized by Agra FSDA,” Times of India. 10/28/17.
–Lagiotis, G., et al., “Detection and quantification of cashew in commercial tea products using high resolution melting (HRM) analysis,” Journal of Food Science. 5/29/20.
–Li, L., et al., “Potential of smartphone-coupled micro NIR spectroscopy for quality control of green tea,” Spectrochimica Acta 247. 2/15/21.
–Rappaport, E. A Thirst for Empire, Princeton University Press, Princeton, 2017.
–Stoeckle, M. Y. et al., “Commercial teas highlight plant DNA barcode identification successes and obstacles,” Scientific Reports 1(42). 7/21/2011.
–Strong, M., “Taiwan destroys more than 280 kg of TWG chamomile tea from Egypt,” Taiwan News. 3/2/21.
–Wei, L., et al., “Rapid detection of carmine in black tea with spectrophotometry coupled predictive modelling,” Food Chemistry 329. 11/1/20.

Teas shown here have been independently tested for purity. From top, TeaHaus chamomile blend, South Korea Seogwang Sencha, and Wild Caucasus Mountain Tea.

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