## 2 Materials and Methods  
The research material consisted of 27 samples of tea of various types from different manufacturers purchased in stores in Lublin (Poland). Six samples of green leafy tea, three samples of pu-erh leafy tea, four samples of white leaf tea, six samples of black leaf tea, three samples of black granulated tea, and five samples of black express tea were purchased. To obtain a homogeneous sample in the case of black express tea, the contents of the bags were spilled and mixed. Tea infusions were prepared according to PN-ISO 3103: 1996 Tea--Preparation of liquor for use in sensory tests. In short, 2 g of tea leaves, smaller than 2 mm and more than 1.5 mm, were added to 100 mL of deionized water (Hydrolab system HLP10p, Poland) at 100 \({}^{\circ}\)C and brewed under cover for 6 min. Then the infusion was filtered through Whatman No.1 to a volumetric flask, and after cooling to room temperature, deionized water was added to make up 100 mL volume. The amount of fluoride in tea infusions was determined by the potentiometric method, according to [PERSON] [40]. That is, 20 mL was taken from the prepared sample, 20 mL of Tisab I (Sigma-Aldrich, St. Louis, MO, USA) solution was added, then the content was mixed, and fluoride was measured by the potentiometric technique. ISE-F/IJ-F Ionode Pty Ltd. (Australia) fluoride ion-selective electrode and the Hi 221 m from Hanna Instruments (USA) were used. Each tea infusion sample was analyzed in three repetitions. A primary solution was prepared to make a calibration curve by adding 10 mL of a certified reference solution of fluoride ions 1000 mg/L \(\pm\) 4 mg/L TraceCERT (Sigma-Aldrich) to a 100 mL volumetric flask. The appropriate volume was measured in a 20 mL volumetric flask from the prepared primary solution to obtain solutions in the concentration range of 0.5 mg/L-10 mg/L. Calibration was performed before each measuring series. To examine the effect of fragmentation of the leaf, the leafy tea samples (green, pu-erh, white, and black) were sieved through the sieve with the size of the stitches 2.5, 2,1.5, 1.02, 0.75, and 0.5 mm, and each of the fractions was brewed for 6 min. The effect of brewing time (2, 4, 6, 8, and 10 min) on the fluoride content in the tea infusion was examined on one sample of each type of tea. In the case of leafy tea, a fraction with the size of leaves smaller than 2 mm and larger than 1.5 mm was used. The correctness of fluoride ion analysis was confirmed by analyzing the certified reference material sample (SPS-NUTR WW1, SpectraPure Standards) and comparison of the obtained measurement value 1.02 \(\pm\) 0.3 mg/L with an accredited value of 1.00 \(\pm\) 0.01 mg/L. Data were analyzed using one-way ANOVA, followed by [PERSON]'s test, using the SAS statistical system (SAS version 9.1; SAS Inst., Cary, NC, USA). The significance of all the tests was set at \(p\leq 0.05\). The health risk assessment (noncarcinogenic hazard) related to the ingestion of fluoride from tea infusion was performed using the target hazard quotient (THQ) calculated by the formula [41]:  
\[\text{THQ}=\text{CDI}/\text{RfD} \tag{1}\]  
where the chronic daily intake (CDI) is the estimated amount of fluoride intake per kilogram of body weight, and the RfD is the oral fluoride intake reference dose of 0.06 (mg/kg/day) [42]. A THQ of \(<\)1 indicates an insignificant risk level, whereas a THQ of \(>\)1 implies a potential noncancer-causing health impact. The CDI value was calculated using the equation:  
\[\text{CDI}=(\text{C}\times\text{DI}\times\text{EF}\times\text{ED})/(\text{BW} \times\text{AT}) \tag{2}\]  
where C is the fluoride concentration in tea infusion (mg/L), DI is the average daily intake rate of tea (L/day), EF is exposure frequency (day/year), ED is the exposure duration (year), BW is body weight (kg), and AT is the averaging time (days). The health risk assessment was carried out with the division of the population in terms of age and gender.