Safety Evaluation of Fluoride Content in Tea Infusions Consumed in the Azores—a Volcanic Region with Water Springs naturally Enriched in Fluoride

Abstract

Tea is the second most commonly consumed beverage in the world. It is well recognized that the consumption of tea in high quantities can promote the development of fluorosis. The main objective of this study is to estimate the exposure to fluoride in the Azores through drinking tea prepared with water from different volcanic locations, by i) investigating the fluoride (F) content of various commercial brands of tea (Camellia sinensis) marketed in Azores and ii) comparing tea releasing rates of F according to brewing time, considering the fluoride concentration in the different types of water used for the infusion. Fluoride contents were determined by ion-selective electrode in 30 samples of drinking water from three different locations and in 450 samples of tea (black and green tea) from three different brands. Fluoride concentration in water ranged from 0.29 to 1.56 ppm (Porto Formoso and Sete Cidades village, respectively). Fluoride concentrations increased with brewing time, reaching the highest values in the Azorean black and green tea infusions. For all the studied brands, a negative correlation was found between tea fluoride contents and the pH of the water used to prepare the infusion. Fluoride concentration in infusions was significantly associated with the background fluoride concentration in drinking water. Since the fluoride concentration in groundwater varies accordingly to the geological conditions and tea consumption can contribute to fluoride intake, it is important to define the limits for tea consumption, particularly in fluoride-rich areas. Graphical Abstract Fluoride concentrations in black and green tea for 3 minutes of brewing time and, association between fluoride concentration and pH with brewing time.

Fluoride in Volcanic Areas: A Case Study in Medical Geology

“…The higher concentration of fluoride in the Azorean tea brands is related to the fact that the soils of the Azores archipelago originate from modern volcanic materials that have evolved under the humid and moderate Atlantic climate, classified as Andosols [65], being naturally enriched in fluoride. With mean results of 3.53 mg/L of fluoride in tea infusions, several concerns regarding the consumption of tea, especially in children, were raised by this study, since by consuming tea the daily intake of fluoride could easily overcome the recommended daily values [64]. This work evidenced that in areas where tea consumption is habitual in all ages and where fluoride content in drinking water exceeds the legislated values, the upper limit threshold for the average fluoride daily Fluoride in Volcanic Areas: A Case Study in Medical Geology DOI: http://dx.doi.org/10.5772/intechopen.86058 intake can be easily exceeded only by tea drinking, contributing to the development of fluorosis in these areas.…”

“…Considering that within the residents of this island, the tea consumption is a well-established habit in adults and children and that tea is a fluoridebioconcentrating plant, another study was developed in 2017 by Linhares et al to assess the exposure of humans to fluoride intake through tea infusion consumption [64]. The authors concluded that the Azorean tea brands had higher fluoride content than other international brands.…”

Fluoride absorption, transportation and tolerance mechanism in Camellia sinensis, and its bioavailability and health risk assessment: a systematic review

“…Fluoride leaching in various products (loose tea leaves and tea bags) depends on sample mass-to-water volume ratio, tea type, infusion temperature, agitation, grain size, water hardness, and background fluoride concentration in water. 98,[100][101][102] Fluoride content increases with infusion duration, infusions of fermented tea also have higher fluoride levels than those of unfermented tea. 4 Much of the fluoride content in tea is released within the initial 30 min of steeping.…”

Exposure Assessment of Fluoride Intake Through Commercially Available Black Tea (Camellia sinensis L.) from Areas with High Incidences of Chronic Kidney Disease with Undetermined Origin (CKDu) in Sri Lanka

“…Tea plants (Camellia sinensis L.) are well-known to accumulate F − during their growth. Subsequently, F − accumulates during the processing of tea and brewing can release it into the infusions [5,7,27,29]. Exposure levels of fluoride through consumption of tea can be evaluated by determination of F − contents in tea infusions [28].…”

“…This makes it an important source of dietary intake [6,37]. In addition, when waters with elevated F − contents are used for preparing infusions, the contents of this critical element can further increase [7,27].…”