Pesticides, trace elements and pharmaceuticals in tea samples available in Belgian retail shops and the risk associated upon acute and chronic exposure

ABSTRACT Over the last decade, the consumption of tea and herbal tea has gained more and more popularity across the globe, but the potential presence of chemical contaminants (e.g. pesticides, trace elements, synthetic drugs) may raise health concerns. This study analysed selected teas available in Belgian retail stores and performed a risk assessment for these samples. No chemical adulteration could be detected in dry tea material. More than 38% of the dry leaves samples contained at least one pesticide exceeding the maximal residue level (MRL) set by the EU. However, further risk assessment, based on the values of pesticide residues and the toxic trace elements encountered in the brew, demonstrate that the consumption of these teas will not give rise to health concerns. Nonetheless, attention should be given to the leaching potential of nickel from teas and the presence of arsenic in brews from algae containing teas.


Introduction
In the last decade, the consumption of tea and herbal tea has gained more and more popularity across the globe. Moreover, market research reports estimate that the consumption of tea and herbal teas have increased almost two fold during the last decade, in a mainly coffee-drinking culture nation such as Belgium (Tea -Belgium | Statista Market Forecast 2021). This increasing trend is mainly attributed to younger people that are consuming less coffee in favour of more fashionable tea based drinks. Traditional tea, produced from the leaves of Camellia sinensis, can be categorised based on the degree of fermentation of the leaves during its processing. Green teas are nonfermented, oolong teas are semi-fermented and black teas are fully fermented (Karak and Bhagat 2010;Schwalfenberg et al. 2013). Additionally, there are herbal teas containing fresh or dried flowers, fruit, leaves, seeds or roots from various herbs or mixtures of herbs which may or may not include C. sinensis leaves The global increase in the consumption of tea and herbal teas can be attributed to their pleasant flavour and their potential health benefits. Tea contains polyphenols, tannic acid and antioxidants which have been associated with a reduced risk of cancer, diabetes, cardiovascular and neurological diseases and antiaging effects (Khan and Mukhtar 2019). Although the number of studies that explored the clinical efficacy of its use and safety is small, no reporting occurred of any detrimental effects from the consumption of medicinal grade plant species as herbal teas (Poswal et al. 2019). Nevertheless, safety aspects need to be evaluated since studies have reported the presence of various contaminants including pesticides, toxic trace elements (i.e. lead, arsenic and cadmium) and chemical adulteration by spiking product with pharmaceutical drugs (Abd El-Aty et al. 2014).
A plethora of different synthetic chemical pesticides are currently being used to combat the great variety of plant pathogens, which could otherwise affect the quality and the quantity of the desired herbal product. The most widely spread pesticides include the organophosphates, carbamates, synthetic pyrethroids, neonicotinoids and benzimidazoles. One of the major disadvantages of the use of pesticides resides in the fact that pesticide residues may remain on the plant at amounts higher than the maximum residue level (MRL). Such pesticide residues can then be transferred to the infusion, posing health hazards. The amount of pesticide that can transfer from the herbal material into the infusion depends on the physico-chemical properties of the pesticide in question and the brewing time. Indeed, the transfer rate of organophosphorus pesticides were reported to range from 0.7% for chlorpyrifos to 90.1% for methamidophos ). Moreover, the transfer rate of chlorpyrifos also differed amongst different studies ranging from 0.7% to 3.1%, 9.1% to 11.7% (Jaggi et al. 2001;Manikandan et al. 2009;Heshmati et al. 2021). These discrepancies can be explained by differences in the type of brewing procedure and the type of tea. Nevertheless, general tendencies can be seenfor example, pyrethroid pesticides exhibited a low transfer tendency, while pesticides belonging to the neonicotinoid group generally have a high transfer potential (Wang et al. 2019). The above mentioned studies mainly focused on traditional green tea or black tea, as these are the most consumed type of tea in their respective countries. In Belgium, herbal teas are becoming popular and it is therefore also essential to determine the amount and type of pesticides that are present in the dried material and the amount of pesticide that transfers in the infusion. Furthermore, as the herbal material for herbal teas generally do not require further processing like fermentation, these teas might potentially contain higher levels of pesticide residues (Xiao et al. 2017).
In addition to the occurrence of polyphenols, tannic acid and antioxidants, the regular consumption of tea can be considered a source of dietary essential elements (i.e. calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P) and zinc (Zn) (Schwalfenberg et al. 2013)). However, several studies have also shown the presence of potentially toxic trace metals like lead (Pb), cadmium (Cd) and metalloids, such as arsenic (As) in herbal teas and their infusions (Han et al. 2006;Shekoohiyan et al. 2012;Schwalfenberg et al. 2013;Milani et al. 2018). In a recent study, de Oliveira et al. (2018) measured As, Cd, Cr and Pb in 47 traditional teas and herbal teas commercialised in the U.S. The authors found that the mean concentrations of As (0.26 mg kg −1 ), Cd (0.19 mg kg −1 ) and Pb (2.32 mg kg-−1 ) in tea leaves were higher in herbal teas compared to traditional teas but in all cases the levels were below the WHO limits for medicinal plants, except for one sample. When the concentrations of As, Cd, Cr and Pb were measured in the infusions, all were below the WHO guidance values for drinking water (de Oliveira et al. 2018). The low concentrations of certain trace elements (i.e. As, Cd, Cr, Pb) can be related to their poor extractability as they are bound to the organic matrix and thus remain in the leaves ). Another study conducted in Spain by Martín-Domingo et al. (2017) showed that nearly 5% of the analysed herbal teas (n = 220) contained Cd levels that surpassed the recommended WHO limit for medicinal plants. High Cd levels were mostly detected in thyme and camomile teas. Though the concentrations of trace metals in the infusions were not shown, the authors concluded that based on the low percentage solubilisation of Cd in the herbal infusion (11%) the intake of Cd from such infusions do not pose a health risk for consumers. A large compilation of studies by Karak and Bhagat (2010) also reported that trace element concentrations in tea infusions are generally low and within safe limits in most of the cases. Nevertheless, in order to assure safe products for human consumption, it is important to regularly monitor the amount of metals and metalloids in tea and herbal teas.
Although many of these teas and herbal teas contain a large amount of beneficial substances, several reports have documented the chemical adulteration of these herbal products with either synthetic pharmaceutical drugs approved by the U.S. Food and Drug Administration (U.S. FDA) and/or the European Medicines Agency (EMA) or non-approved drugs (Al Lawati et al. 2017;Hackl 2019;Jairoun et al. 2021). The majority of these adulterated herbal teas encountered in Belgian market originate from samples purchased online; however, the incidence of such products in retail shops can never be 100% excluded (Hackl 2019).
The overall aim of this study was to generate a global cumulative overview of the risks associated with the consumption of teas and herbal teas commercialised in Belgium to better asses if they pose a risk to human health. Thus, the objectives of the study were to (1) determine the content of pesticides, toxic trace elements and synthetic pharmacological residues in various tea and herbal tea samples available on the Belgian market, (2) to determine the transfer rate of these contaminants in the infusions and (3) to estimate the short-term and long-term risk for the consumer health.

Sampling
In order to be the most representative of the Belgian consumption habits, 55 tea samples of the most widespread brands were bought in local stores. Specific shops such as organic shops and dedicated tea shops were also included. Different tea types were selected i.e. black, green, white, flavoured, oolong, as well as commonly used herbal teas, i.e. camomile, mint, rooibos, senna in order to reflect the variety of products available in Belgium. To ensure the representativeness of samples taken at retail stores level, one package or unit were taken. For samples in bulk, a minimum of 100 g of tea leaves were purchased.

Tea and herbal tea preparation and infusion
After arrival in laboratory, half of each tea and herbal tea leaves samples were ground to a fine powder and homogenised by a mixer (IKA M20, IKA®-Werke GmbH & Co. KG, Staufen, Germany) prior to contaminant analysis in dry material. The remaining part were kept to generate the brew. Tea infusions were prepared following ISO 3103 (2019): 2 g of dry tea leaves were placed in blank tea bags and 100 mL of boiled distilled water was added. The tea bags were left to stand for 6 min and thereafter removed without stirring. Solvents, reagents and standard solutions are described in Section S1 of the Supplementary information and quality assurance and method related to the extraction procedures of contaminants from dry material and infusion are provided in Section S2 of the Supplementary information.

Pesticides
To evaluate the acute risk for consumer's health the acute hazard risk index (aHI) was calculated. The aHI expressed as a percentage is calculated as the ratio between the IESTI (International Estimated Short Term Intake) values (expressed in mg kg −1 body weight −1 day −1 and the acute reference dose (ARfD), for both adults and children, according to the equations aHI ¼ IESTI ARfD À � x100 and IESTI ¼ ðLPxHRxTR)/bw, where LP (Large portion) is the 97.5 th percentile of the tea leaves portion size taken by the consumer (0.008 and 0.021 kg day −1 for children and adults, respectively). HR is the highest residue level found in tea leaves for a specific pesticide (mg kg −1 ), TR is the transfer rate of pesticides from tea leaves into tea infusion during brewing and bw is the mean body weight for the targeted population (children or adult) in kg. According to FAO JMPR experts (FAO 2015) a risk exists when the aHI is greater than 100%. All these values have been calculated with the use of the pesticide residue intake model (Primo) made available by the European Food Safety Authority . No ADI and ARfD values were available for anthraquinone and biphenyl. However, based on toxicological studies, the European Chemical Agency (ECHA) has put the no adverse effect level (NOAEL) for oral administration of anthraquinone at 1.36 mg kg −1 body weight per day and of biphenyl at 38 mg kg −1 body weight per day (Anthraquinone -Registration Dossier -ECHA, 2022). A common way to approximate the ADI is to use a 100 fold factor on the NAOEL (Chemicals Regulation Directorate 2013). Hence, ADI values of 0.0136 and 0.38 mg kg −1 bw per day have been used.
To evaluate the chronic risk for the consumer health, the estimated daily intake (EDI) is calculated according the equation EDI ¼ ðIRxMCxTR)/bw, where IR is the mean tea ingestion rate (kg day −1 ). As no clear average consumption values were available for both children and adults in the primo model, we decided to utilise a daily intake value of 0.010 kg day −1 as this represents the median value of the different ingestion rates reported in the literature, which demonstrated that tea consumption can vary widely among different population groups and habits. Ingestion rates of tea of 6 g day −1 (Polechońska et al. 2015;Martín-Domingo et al. 2017), 10 g day −1 (Yuan et al. 2007;Sofuoglu and Kavcar 2008;Na Nagara et al. 2021) and 13 g day −1  have been previously reported. Moreover, as no reliable information on the chronic intake for children was available; hence, the chronic risk was evaluated for adults only. MC is the mean concentration of residue levels found in tea leaves for a specific pesticide (mg kg −1 ), TR is the transfer rate and bw is the mean adult body weight of 70 kg. Then, the health hazard quotient (HQ) expressed as the ratio between the EDI and the ADI has been calculated according to HQ ¼ EDI ADI À � x100. A chronic risk exists when the percentage of HQ is greater than 100%.

Trace elements
For trace elements the potential chronic health risk of exposure from drinking tea infusion was assessed from the EDI, which was calculated from the selected samples that were brewed (n = 17). For risk evaluation, the calculated EDI for each trace element was compared against the appropriate health based guidance values (i.e. tolerable daily intake, tolerable weekly intake, tolerable upper intake level) or the benchmark dose lower confidence limit (BMDL). For As, the benchmark dose lower confidence limit (BMDL 01 ) of 0.3 µg kg −1 bw day −1 was used as recommended by Arcella et al. (2021). For Cd, the tolerable weekly intake (TWI) of 2.5 µg kg −1 bw was used (EFSA 2012a). For Ni the tolerable daily intake (TDI) of 13 µg kg −1 bw was used (Schrenk et al. 2020). The guidance value used for Pb was the BMDL 10 of 0.63 µg kg −1 bw day −1 for nephrotoxic effects on adults (EFSA CONTAM Panel 2010). For Cu and Zn which are also essential elements, the tolerable upper intake level as determined by EFSA (2006) was considered, 25 mg day −1 for Zn and 5 mg day −1 for Cu.
Risk values were calculated using two different approaches: For elements where the health-based guidance value is indicated as TDI, TWI or tolerable upper level, i.e. Cd, Cu, Ni and Zn, the EDI was divided by their respective guidance value and thus presented as a percentage. For As and Pb which are both genotoxic and carcinogenic contaminants and for which no threshold values are established the margin of exposure (MOE) approach was used following recommendation by EFSA (2005). In this case, the BMDL was divided by their respective EDI. The MOE approach evaluated the potential risks associated with the presence of the contaminant in the tea infusion.
Acute toxicity was only determined for As. A minimal risk level of 5 µg kg bw −1 day −1 for acuteduration oral exposure to inorganic As derived by the Agency for Toxic Substances and Disease Registry (ATSDR) was used (U.S . Department of health and human services 2007). In this case, the risk value was calculated as the ratio between EDI and the acute minimal risk level and presented as a percentage.

Pesticide residues in dry material
A total of 55 different tea and herbal tea samples were analysed for the presence of a total of 250 different pesticides. The number and type of pesticide residues varied amongst the studied samples. A total of 7.3% of the samples did not contain any detectable amount of the analyzed pesticide residues, while 65.5% contained 1 to 5 residues, 14.5% contained 6-10 residues and 12.7% contained more than 10 residues with a maximum 14 residues. From the 55 analyzed samples, 21 (38.2%) contained at least one pesticide in quantities that exceeded its maximum residue level (European Commission 2005) and consequently did not comply with the EU legislation, taking an extended measurement uncertainty of 50% into account (Table 1). The detailed occurrence data of the pesticide residues present in the dry material of each sample can be found in Table S1. These findings are in agreement with recent findings by Heshmati et al. (2021), who found that approximately 40% of black tea samples analyzed for the presence of 33 pesticides were non-compliant. The most abundant pesticide residues that exceeded the MRL belonged to either to the pyrethoid and PAH family as can be seen in Table S2. The insecticide cyhalothrin-L was responsible for 9 of 21 noncompliant samples while the polycyclic aromatic hydrocarbon anthraquinone was responsible for 6 out of these 21 samples. These families belonged to the most frequently encountered pesticides (n > 5 detected in the sample set) as demonstrated in Table 2. This list is similar to findings of  and Fan et al. (2022) who analyzed tea leaves produced in China. This similarity make sense since most tea sold in Belgium originates from this area. In addition to the PAHs (e.g. anthraquinone and biphenyl) and the pyrethroids (e.g. bifenthrin, cyhalothrin-L, cypermethrin), also the neonicotinoids (e.g. acetamiprid, imidacloprid, thiamethoxam, thiachloprid) were abundantly present. These later two classes of insecticides are known to be commonly used for pest control on tea plantations as a result of their broad-spectrum activity (Chen et al. 2014;Abd El-Aty et al. 2014;Xiao et al. 2017;Ikenaka et al. 2018;Zhang et al. 2020; Thompson et al. 2020;Nimako et al. 2021). Additionally, the PAH anthraquinone was detected 16 times, making it the second most detected pesticide, although its use has been banned by the EU. These findings are consistent with the findings of Díaz-Galiano et al. (2021) where they found that 48% of their tea samples, from different European countries, contained detectable amounts of this compound. However, prior studies have shown that origin of a contamination with this residue is not necessarily due to illegal use of phytosanitary products, but could also be due to an environmental pollution from natural and man-made processes of combustion (e.g. mineral oils, wood and charcoal and their products of combustion) or could be the result of a contamination occurring through drying or roasting processes (EFSA 2012b; Wang et al. 2018;Anggraini et al. 2020). A similar argument could also be made for biphenyl (EFSA 2012b).

Pesticide residues in tea brew
A common interest regarding any chemical compound in food is how much of it is actually ingested by the consumer. For this purposein this case, tea leaves with sufficiently high pesticides content were infused to determine their presence in tea brew. The obtained TR values are listed in Table 2 and varied from 1% (e.g. bifenthrin and cypermethrin) to 78% (imidacloprid). The different TRs are related to the amount present in the dry material, their solubility rate in water and their partition coefficient log P ow (Abd El-Aty et al. 2014). While the high values for thiamethoxam (62%), imidacloprid (78%) and acetamiprid (54%) are in line with the transfer rates obtained by Hou et al. (2013), the low TR values (≤10%) for bifenthrin, buprofezin, chlorothalonil and cypermethrin are very likely due to their high partition coefficients (log P ow >4). For this reason and due to the lack of relevant pesticides content in dry tea, no reliable TR could be determined for biphenyl, chlorfenapyr, chlorpyriphos-ethyl and cyhalothrin-L. As their log P ow values are above 4, a maximal theoretical TR of 10% has been used for these compounds in order to perform a risk assessment. Mepronil was not found in any tea infusion, as its Log P ow is 3.66, so below 4. Therefore, the theoretical TR of 10% has not been used and no risk assessment has been performed for this compound since its concentration does not represent a risk for consumer's health.

Total element concentration in dry tea leaves
The trace element concentrations for the samples are given in Table S3, while Table 3 summarises the mean, minimum and maximum concentrations. In general, Mn and Fe were the most abundant elements in tea leaves and the measured concentrations compared well with values reported for tea samples elsewhere (Polechońska et al. 2015;Podwika et al. 2018;Milani et al. 2018). The highest Mn concentration was observed in a type of green tea, "greeting pine," whereas the lowest concentration was obtained in two types of herbal teas that do not contain C. sinensis. Tea is a plant that grows well in acidic soils with pH 5-5.6 (Mehra and Baker 2007) and in such conditions metals can be freely available for plant uptake. Therefore, the large concentrations of Mn and Fe in tea leaves can be explained by their high bioavailability and the capacity of the plant to accumulate such metals.
The concentration of Zn, Cu and Ni vary greatly between the different types of tea analysed. Nevertheless, the mean total concentrations were comparable to those reported in previous work. For example, Milani et al. (2016)  analyzed 30 tea samples that were purchased in Brazil and found Zn concentrations ranged between 21 and 44 mg kg-−1 , Cu between 12 and 19 mg kg −1 and Ni between 3.53 and 5.30 mg kg −1 .
The trace elements As, Cd and Pb are listed in the WHO top 10 of chemicals that pose a public health concern. They are considered environmental pollutants and although they are not essential elements for plants they can be taken up by plant roots and accumulate in plant tissue. Although no global limits are set for herbal tea material, the matrix is quite similar to herbal drugs and therefore the limits set by the WHO for, Cd and Pb are often utilised for risk assessment on dry herbal tea material or dry material for herbal infusion. These limits for Cd and Pb correspond to 0.3 and 10 mg kg −1 , respectively (World Health Organization 2007). In this study, only one tea sample exceeded the limit of Pb almost 4-fold and one tea sample was just above the limit for Cd with 0.34 mg kg −1 (Table S3).

Total element concentration in tea infusions
Trace element analysis was conducted on 17 infusions that were prepared following the standard procedure. It is well known that the concentration of elements in the infusion may depend on various factors, i.e. type of tea, initial total elemental content and speciation, infusion time, tea to water ratio, water temperature and the extraction efficiency of each element (Karak and Bhagat 2010;Welna et al. 2012). As shown in Table 3 the transfer rate of each element varied   (2017), Guidelines for drinking-water quality: fourth edition incorporating the first addendum, Geneva.
widely. Iron, Pb and Cd had the lowest release in the infusions (<10%), whereas Ni, As and Co had the highest release (30% to 57%). Based on the extraction percentage, Welna et al. (2012) classified elements in three groups: highly extractable (>55%, i.e. Co and Ni) moderately extractable (20-55%, i.e. Cu, Mn and Zn) and poorly extractable (<20%, i.e. Fe). Elements that are highly and moderately extractable can be of concern if the total concentration in the leaves is high because the expected levels in the infusions can be as well high.
The elemental concentrations of As, Cd, Ni and Pb are summarised in Table 3. Arsenic was detected in all tea infusions, but concentrations were in general low (<3 µg L −1 ), except for two samples with high total As levels in dry tea leaves for which the measured concentrations were 38 µg L −1 and 50 µg L −1 . If the WHO guideline for drinking water is considered to estimate potential risk, then these two samples were 3.8 and 5 times higher than the 10 µg L −1 limit for drinking water (World Health Organisation 2017). The two tea samples high in As contain bladderwrack (Fucus vesiculosus), a type of seaweed used in herbal teas that claim slimming properties. Since, the toxicity of As depends on the As species exposed to, speciation analysis is necessary for a correct risk assessment. Studies that determined As concentration and speciation in seaweed species found that inorganic As is generally a minor component and that arsenosugars are the dominant water-extractable species in seaweeds (Taylor and Jackson 2016). Therefore, a minor experiment was performed to analyse the species distribution of As extracted from the two algae-based infusions using high-performance liquid chromatography (HPLC) coupled with ICP-MS (data not shown). Results showed that inorganic As represented less than 1% of the total As in the infusion (0.29 µg L −1 ). The speciation results are relevant for risk assessment because inorganic As is the most toxic species to human and current regulatory guidelines are based on this species. The toxicity of the arsenosugars is not well documented yet, which complicates the risk interpretation.
Concentrations of other toxic elements Cd, Ni and Pb in the infusions were below the WHO drinking water guidelines (World Health Organisation 2017), except for Ni in five samples (Tables 3 and S4). Cadmium and Pb are less of a concern since these elements practically do not extract in tea. However, Ni may be an element of interest since it is highly extractable and its contribution in the infusion may be large if the initial concentration in the leaves is high too.

Pharmacological residues in dry material
None of the samples bought in retail shops contained a detectable quantity of synthetic active pharmaceutical compounds, indicating that chemical adulteration is unlikely for those product brands present in popular retail shops. However, both samples T-1-36 and T-2-164 were positive for the presence of sennosides, known anthraquinone glycosides, but did not contain detectable amounts of anthraquinone (Table 1). These sennosides are very likely originating from the senna plant Senna alexandrina, conform with the herbal ingredients listed on the label of the samples. The occurrence of this plant in herbal teas is by Belgian law not forbidden and does not automatically classify this tea as a medicinal herbal preparation. However, in 2018 the presence of sennosides in food supplements became under scrutiny by EFSA. The agency gave the advice to not use products containing senna for more than two consecutive weeks and the recommended daily intake should not exceed 18 mg (expressed as sennoside B) nor should it be administered to children (EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) et al. 2018). Moreover, also the EMA set a typical recommended dose for herbal teas containing 15-30 mg of sennosides once or in case of 15 mg, twice a day and this for a very short-term use only, as put forward in the assessment report of the EMA (Committee on Herbal Medicinal Products 2018).

Pesticides
As summarised in Table 4, all calculated IESTI and concurrent acute hazard risk index (aHI) values did not exceed 100% for both adults and children, thus indicating that there was no acute risk associated with the consumption of these teas. This can be explained by the fact that for those pesticides where relative high concentrations were found in the samples with low ADI and/or ARfD, so being the most toxic, low transmission rates were observed. All EDI values and concurrent hazard quotients (HQ) did not exceed 100%, indicating that there is no risk associated with daily consumption of tea leaves. These results are in accordance with Fan et al. (2022) and  where they determined HQ to be much lower than 1%.
Altogether, solely based on the risk assessment performed for pesticide residues, it can be stated that the consumption of these teas does not represent any acute nor chronic health risk for the consumer, although 40% of the samples were not compliant to EU regulation. However, the MRLs encompass not only the acute risks to human health upon oral consumption, but are also set taking into account good agricultural practices.

Trace elements
The EDIs of trace elements from tea consumption are presented in Table 5. For As it was assumed that the concentration of As in the brew was inorganic As, except for the two samples where measured As concentration in the infusion was high. For these two particular samples, the calculated EDI was multiplied by 0.01 since the results from the speciation analysis showed that just 1% of total As in the infusion was inorganic As. Since we cannot rule out that the other tea infusions with much lower concentrations contain only inorganic As, we propose this approach as the worst case estimation.
As described before, different approaches were followed for risk characterisation of the different contaminants. This distinction was done considering the type of health-based guidance value. For elements where a chronic maximum intake rate has been established and expressed either as a TDI, TWI or upper level, the risk was evaluated as the percentage contribution of the guidance value. As shown in Table 5 the average calculated exposure for Cd, Cu, Ni and Zn was below 3% and thus it is unlikely that the consumption of tea can pose a risk of adverse health effects for those elements. The highest calculated risk exposure value was for Ni in one tea sample, which contributed with about 9% of the TDI. This value is somewhat close to the range values reported by Milani et al. (2016) for C. sinensis tea (0.3-6.8% of TDI).
For Arsenic and Pb the MOE methodology was used to interpret possible risks associated to its exposure. The average and range MOE values for As and Pb are presented in Table 5. There are no clear guidelines on how these values should be interpreted nor a desired MOE has been given for As. However, a MOE of 100 as a threshold of concern was proposed by Cheyns et al. (2021) as an indicative of low health concern for food supplements. For Pb, the EFSA CONTAM Panel (2010) concluded that a MOE > 10 would ensure no appreciable health risk. Even for a MOE > 1 the risk would be very low. MOEs for Pb were in general very high except for one tea for which the MOE was only 2. However, based on the conclusion by EFSA this low MOE is of low health concern, as it is larger than 1. For acute exposure to inorganic As the average calculated exposure was 0.1%, with a range between 0.003% and 0.56% of the minimal risk level for acute toxicity. These results indicate  health guidance values used to evaluate chronic toxicity were: tolerable weekly intake of 2.5 µg Cd/kg bw/week; adult tolerable upper intake level of 5 mg Cu/day and 25 mg Zn/day; tolerable daily intake of 13 µg Ni/kg bw/day. For As and Pb the benchmark dose lower confidence limit of BMDL 01 0.3 µg As/kg bw/day and BMDL 10 0.63 µg Pb/kg bw/day were used. b The guidance value for acute toxicity is a minimal risk level of 5 µg As/kg bw/day. that no acute toxic effects are to be expected from drinking herbal teas.

Drugs and medicines
As no synthetic drug was encountered in the analysed samples, it can be stated that at least for the presence of synthetic drugs, there was no risk associated for the consumption of these teas. However, two samples were positive for the presence of sennosides originating from the senna plant. Although, the use of over the counter senna containing herbal teas, for only a limited period of time by healthy adults, has been associated with few side effects (Senna 2012), an acute overdosis of sennosides or a patients/consumers sensitivity to sennosides could result in symptoms such as griping pain and severe diarrhoea. Long term use or abuse can lead to "cathartic" colon with diarrhea, cramps, weight loss and darkened pigmentation of the colonic mucosa. Moreover, even toxic hepatitis has been reported (Vanderperren et al. 2005;Ish et al. 2019;Haoudar et al. 2021). Additionally, both EMA and EFSA state that the use of these preparations should be limited in time and should not be administered to children under the age of 12 and pregnant or lactating women. Unfortunately, for these 2 specific samples, the external packaging and the tea bags did not disclose any warning on the contraindication for the consumption by children or pregnant or lactating women nor was there information on the restriction in time associated with the use of such a potent herbal food commodity.

Conclusion
This study assessed the health risks associated with the consumption of herbal teas marketed in Belgium. Our findings demonstrate that intake of teas sold in retails shops in Belgium is rather safe. However, care has to be taken as this study does not take into account the arise concern about the presence of pesticide cocktails or pesticides with endocrine disruptors effect. Moreover, as a lot of tea samples exceeded EU MRLs for pesticides residues. The MRL values encompass not only the acute risks to human health upon oral consumption, but are also set taking into account chronic exposures at the consumers and production end and environmental effects to the ecosystem.