Tea is the second most consumed beverage worldwide after water. Tea and water together can never go wrong but researchers at the American Chemical Society have discovered disinfection byproducts (DBPs) in tea which might have harmful effects.
Chlorine is the most used chemical to disinfect drinking water globally. When boiled tap water is used to brew tea, residual chlorine in the water can react with tea compounds to form disinfection byproducts (DBPs). The researchers of the study, published in Environmental Science & Technology, measured 60 DBPs in three types of tea. They also detected many unknown DBPs with uncertain health effects.
Disinfecting water is an important process to ensure safety but the residual DBP formation is when the issue turns serious. Tea contains about 500 compounds, including polyphenols, amino acids, caffeine and others, that can react with chlorine to form DBPs, some of which have been linked in epidemiological studies with cancer and adverse birth outcomes.
In addition, DBPs can form from reactions with compounds in the tap water itself. Ms. Susan Richardson, a chemistry professor at the University of South Carolina and colleagues wanted to conduct a comprehensive survey to measure 60 known DBPs in three green and black teas popular in the US.
The researchers brewed the teas and then measured the compounds using gas chromatography-mass spectrometry. Levels of the 60 DBPs were higher in tap water than in the brewed teas, likely because many compounds evaporated or were absorbed by tea leaves.
However, the 60 known DBPs accounted for 4 percent of total organic halogen which is a measure of all halogen-containing DBPs in tea, indicating that the majority of these compounds in the tea remain unknown.
For the first time in the beverage, the researchers discovered 15 of the compounds, which are likely formed when chlorine reacts with natural phenolic and polyphenolic precursors in tea leaves. Although no “safe” levels have been determined for most DBPs, the researchers calculated that an average person would need to drink 18-55 cups of tea per day to exceed the limits set by the US Environmental Protection Agency.