Scientists have found that the levels of 60 known disinfection byproducts (PPD) in brewed tea are significantly lower than in the original tap water. At the same time, experts found about 500 compounds in the finished drink that can react with chlorine to form new, as yet unknown and possibly harmful by-products. The results of the study were published in the journal Environmental Science & Technology.
Chlorine is used to disinfect boiled tap water, which is usually used for brewing tea.
American researchers from the University of South Carolina and their Chinese colleagues from Tianjin University measured the levels of 60 known PPD in three popular brands of green and black tea. It turned out that the levels of these substances in brewed tea are lower than in the original tap water. Scientists explained this by the fact that many compounds evaporated during brewing or were absorbed by the tea leaves.
At the same time, it turned out that there are many unknown PPD in the finished tea, the impact of which on human health has not been studied, but, according to the authors, tea contains about 500 compounds, including polyphenols, amino acids, caffeine and others that can react with chlorine to form PPD. For some of them, a link with the risk of developing cancer and complications during pregnancy and childbirth has previously been proven.
Using gas chromatography and high-resolution mass spectrometry, scientists for the first time identified 15 of these compounds, which, according to the authors of the study, are formed by the reaction of chlorine with natural phenolic and polyphenolic precursors in tea leaves. PPD can also occur from reactions with compounds in the tap water itself.
The total amount of organic halogens, representing the bulk of PPD, in tea was about twice as high as in the original tap water. About 4% of them were identified. The main mass-more than 12% – consists of dichloroacetic acid, trichloroacetic acid and chloroform, which were still in the composition of the source water.
Although about 96% of the total amount of organic halogens in tea remained undiagnosed, their concentrations, according to the researchers, do not pose any danger to humans. To exceed the level of these substances that is safe for health, you will have to drink more than 50 cups of tea every day.
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