Assessment of the Potential Health Risk of Heavy Metal Exposure from the Consumption of Herbal, Black and Green Tea

This study attempted to assess the potential risk of heavy metal exposure from the daily consumption of herbal and true tea due to their toxic effects which could result in serious carcinogenic side effects and its environmental impact via Estimated Provisional Weekly Intake (EPTWI) results and comparing it to the Accepted Provisional Weekly Intake (APTWI) set by the Food and Agricultural Organization/World Health Organization Joint Expert Committee on Food Additives (JECFA). Focus was given to the following elements: Lead (Pb), Cadmium (Cd) and Chromium (Cr), as well as nontoxic elements including; Iron (Fe), Manganese (Mn), Nickel (Ni), Zinc (Zn), Copper (Cu), Cobalt (Co) and Tin (Sn), which were analyzed using Inductively Coupled Plasma/Optical Emission Spectrophotometer (ICP-OES) after sample preparation (digestion) using high performance microwave. The results showed Mn and Cd were the highest (991.8 ± 66.2 μg/g) and the lowest (0.09 ± 0.03 μg/g) in both herbal and true tea samples, respectively. At maximum concentration the estimated exposure ranged from 0.0007 μg/g/bw/week of the EPTWI for (Ni) element to 0.0026 μg/g/bw/week of the EPTWI for (Mn) element. These results were found to be not significant in terms of potential consumption risks of all tested brands, when compared to the APTWI.


Introduction
Tea (Camellia sinensis L.), is one of the most popular nonalcoholic beverages, consumed by over two-thirds of the world's population for its medicinal, refreshment and mild stimulant effects [1]. Tea leaves contain polyphenols such as epigallocatechin 3-gallate, which has many medicinal properties, including antioxidant, of soil, which affects its characteristics as well as its physical, chemical and biological properties negatively. This damage can influence all the living organisms whether directly or indirectly [6].
The frequent use of fertilizers and pesticides in Egypt has led to the accumulation of heavy metals, resulting in soil contamination [7]. Some of these metals include Lead (Pb), Cadmium (Cd) and Chromium (Cr) are not degradable, so they tend to transfer from the soil to plants [8].
Especially in industrial zones, which possesses higher levels of heavy metal accumulation in its agricultural lands, when compared to other zones. Therefore, this transfer of heavy metals is one of the key pathways for human exposure, via the food chain, when considering air and water [9]. 'Heavy metals' is a term that applies to a group of metals with similar chemical properties. Some of them exist naturally, while others have emerged from pollution [10].
Essential metals including Copper (Cu), Iron (Fe) and Zinc (Zn) play an important role in the body to maintain normal functions, when present at trace elements [11,12]. Other heavy metals possess high risk to human health such as Pb, Cd and Cr, these metals are on the list of the most dangerous metals that cause chronic diseases and have carcinogenic complications as well [13,14]. In this study, toxic heavy metals including Pb, Cd and Cr next to non-toxic metals including Mn, Ni, Zn, Cu, Co, Sn and Fe were mainly chosen for dietary exposure assessment, in diverse brands of black, green and herbal tea samples collected from Egyptian markets with different production dates, to evaluate their possible toxicity.  [15] to ensure the safety of these tea samples.
Despite several studies done by [16,17], recommend routine checks, and several analyses are always in a requirement, with the intention of avoiding the risks associated with exceeding the intake beyond the tolerance limit standards, and to ensure as well as safeguard their quality and availability.

Sample Collection
The total number of tested samples is 35 of commonly consumed ones in Egypt (Cairo) which represents four marked brands of black tea, three brands of green tea, and two brands of herbal tea. The samples were collected from local markets with different production dates.

Apparatus
A PerkinElmer Optima 8300 inductively coupled plasma optical emission spectrometer equipped with ultrasonic nebulizer U5000 AT+ (CETAC), auto sampler S10, whisper cool (Poly science) and air compressor was used for determination of elements. Plasma

Reagents
Reference standard solutions were prepared from metal stock standards from Merck (1000 mg/l) and were diluted to the corresponding metal solution. Intermediate standard solutions, spiking mixture standard solutions and calibration standard solutions were prepared by diluting up to 100 ml with 2% of HNO3 for obtaining different concentrations.

Sample Preparation
The following two methods were adopted for this study and were commonly used for preparation of Black, Green and herbal tea samples Sample Digestion: Based on the method described by [18], 1 g of each black, green and herbal tea samples was weighed into the microwave digestion vessel. 4-5 drops of de-ionized water and 8 ml nitric acid (69 %) were added to the digestion vessel and then 2 ml of hydrogen peroxide was added (30 %). The vessel was carefully placed in the microwave oven. A thermocouple probe was inserted in the reference vessel to start the cycle. Then, vessels were cooled in a water bath for about 30 minutes. 0.2 ml of Lu was added from Intermediate standard solution (100 mg/L) and volume was completed up to 50 ml using de-ionized water. The microwave oven program was adjusted as in the following Table 1.

Statistical Analysis
The results were expressed in mean±SD (Standard deviation).
Data analysis of the obtained results was performed using Microsoft Excel.

Linearity and Calibration Curves
The linearity of calibration curves was evaluated based on the

Heavy Metal Profile in Black, Green and Herbal Tea Digested Samples and Their Infusions
After running the samples, the results of total concentrations of studied heavy metals in black tea samples and their infusions    The results of total concentrations of studied heavy metals in herbal tea samples and their infusions

Mean Concentrations of Heavy Metals in different Brands of Tea Samples and their Infusions
Regarding the obtained results in Figure 1

Chronic Dietary Exposure Assessments for Maximum Metal Concentrations in Black, Green and Herbal Tea Infusions
Due to the lack of information considering the maximum allowable levels of heavy metals in tea samples, chronic dietary other studies [22].   There should be information for specifying the acceptable concentration of heavy metals in tea and herbal leaves and the maximum allowable and safe concentration of each metal in tea leaves is urgently needed. Therefore, occasional check and frequent analysis of foodstuff is recommended with an intention to avoid any risk that arise from intake beyond the tolerance limits standards. Additionally, this study can be used as a reference for future in depth studies. This research can serve as an eye opener to consumers, manufactures, and the professionals in the health care system due to possible direct or cumulative effects it may cause if high concentration is present.