Evaluation of heavy metal concentration in imported black tea in Iran and consumer risk assessments

Assessment of carcinogenic and non-carcinogenic risk of exposure to potentially toxic elements in tea infusions: Determination by ICP-OES and multivariate statistical data analysis

BACKGROUND

The perennial evergreen tea (Camellia sinensis) plant is one of the most popular nonalcoholic drinks in the world. Fertilizers and industrial, agricultural, and municipal activities are the usual drivers of soil contamination, contaminating tea plants with potentially toxic elements (PTEs). These elements might potentially accumulate to larger amounts in the leaves of plants after being taken up from the soil. Thus, frequent monitoring of these elements is critically important.

METHODS

The present study intended to determine PTEs (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in both tea leaves and infusions using ICP-OES. Various multivariate data analysis methods such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to elucidate the potential sources of PTEs contamination, whether from anthropogenic activities or natural origins. Additionally, Pearson's correlation coefficient (PCC) was calculated to assess the relationships between the variables under study.

RESULTS

The mean contents (mg/L) of all studied elements in tea infusions decreased in order Mn (150.59 ± 1.66) > Fe (11.39 ± 0.99) > Zn (6.62 ± 0.89) > Cu (5.86 ± 0.62) > Co (3.25 ± 0.64) > Ni (1.69 ± 0.23) > Pb (1.08 ± 0.16) > Cr (0.57 ± 0.09) > Cd (0.46 ± 0.09) > Al (0.05 ± 0.008), indicating that Mn exhibits the highest abundance. The mean concentration trend in tea leaf samples mirrored that of infusions, albeit with higher concentrations of PTEs in the former. The tolerable dietary intake (TDI) value for Ni and provisional tolerable monthly intake (PTMI) value for Cd surpassed the standards set by the WHO and EFSA. Calculated hazard index (HI < 1) and cumulative cancer risk (CCR) values suggest negligible exposure risk.

CONCLUSION

Elevated levels of PTEs in commonly consumed tea products concern the public and regulatory agencies.

Unlocking the elemental signature of European tea gardens: Implications for tea traceability

This study presents a comprehensive analysis of the elemental profiles of tea leaves coming from plants grown in several European gardens, with a focus on the bioaccumulation of essential and potentially toxic trace elements in relation to processing and location of tea garden. Samples were collected from various gardens across Europe, including Portugal, the Azores, Germany, the Netherlands, and Switzerland. Elemental analysis was conducted on fresh tea leaves, dried leaves, and leaves processed for the production of green and black tea, along with soil samples from the root zones of tea plants. The results reveal no significant differences in elemental content based on the processing of tea leaves. However, distinct elemental profiles were observed among tea leaves of plants grown in gardens from different European regions. Utilizing chemometric and machine learning tools, the study highlights the potential of these elemental profiles for enhancing the traceability of tea products.

Comparison of Essential and Toxic Metals Levels in some Herbal Teas: a Systematic Review

In the present study, we reviewed the literature as a systematic review to investigate the concentration of some metals (essential, none essential, and toxic metals) in herbal teas and their health risks. The search extended the literature from the database, including Google Scholar, PubMed, and Scopus, using the terms "herbal teas" combined with "heavy metals, essential metals, thyme, rosemary, chamomile, and tea" also with "iron, zinc, aluminum, chromium, cobalt, nickel, manganese, arsenic, cadmium, and lead" in titles and abstracts. The search was limited to articles published from 2012 to 2023 years. Initially, 212 articles were found; by detailed consideration, only 49 papers fit the inclusion criteria and were selected for further study. The mean of metal concentration, standard deviation, data distribution, and sample size were applied to generate data from the articles. The results indicated that all commonly consumed herbal teas included metals. None of them meet the requirements of the WHO requirements. However, more than 70% of their health risks are acceptable. The risks of arsenic and lead in tea and cadmium in black tea were considerably higher than in others. According to the review results, it is important to prevent heavy metal contamination of herbal teas by modifying cultivation patterns and also to prevent to consumption of low-quality herbal teas.

The Potential Use of Near Infrared Spectroscopy (NIRS) to Determine the Heavy Metals and the Percentage of Blends in Tea

The following study analyzed the potential of Near Infrared Spectroscopy (NIRS) to predict the metal composition (Al, Pb, As, Hg and Cu) of tea and for establishing discriminant models for pure teas (green, red, and black) and their different blends. A total of 322 samples of pure black, red, and green teas and binary blends were analyzed. The results showed that pure red teas had the highest content of As and Pb, green teas were the only ones containing Hg, and black teas showed higher levels of Cu. NIRS allowed to predict the content of Al, Pb, As, Hg, and Cu with ratio performance deviation values > 3 for all of them. Additionally, it was possible to discriminate pure samples from their respective blends with an accuracy of 98.3% in calibration and 92.3% in validation. However, when the samples were discriminated according to the percentage of blending (>95%, 95-85%, 85-75%, or 75-50% of pure tea) 100% of the samples of 10 out of 12 groups were correctly classified in calibration, but only the groups with a level of pure tea of >95% showed 100% of the samples as being correctly classified as to validation.

Trace elements in tea in Ouargla, Algeria and health risk assessment

Tea is one of the most common drinks, consumed for its pleasant flavour and several medicinal values. The present study aimed to determine the levels of trace elements in tea products marketed in the Saharan region of Ouargla, Algeria and to evaluate the health risks associated with its regular consumption in adults and infants. To this aim, 78 tea samples were analysed by Inductively Coupled Plasma - Mass Spectrometry. Tea samples appeared to be contaminated by lead (0.73 ± 0.08 µg g-1) and aluminium (0.22 ± 0.02 µg g-1). Cadmium, arsenic, mercury, cobalt, manganese, nickel, chromium, zinc and copper were also detected. General linear model analysis indicated that black tea samples were the most contaminated. Tea samples packed in tea bags were the most contaminated with arsenic, aluminium and manganese. The hazard index was 0.28 and 1.33 for adults and for infants, respectively, indicating adverse non-carcinogenic effects in infants.

The use of banana peel as a low-cost adsorption material for removing hexavalent chromium from tannery wastewater: optimization, kinetic and isotherm study, and regeneration aspects

When the concentration of hexavalent chromium (Cr(vi)) in the environment is greater than a certain limit, it becomes a global concern. Thus, the aim of this study was to use banana peel as an adsorbent to remove heavy metals, specifically Cr(vi) ions from wastewater. Banana peel (BP) was activated in a furnace for 2 h (h) at 450 °C and 50% humidity. Subsequently, the activated BP was characterized by proximate analysis, elemental analysis, scanning-electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) analysis, and thermogravimetric analysis (TGA). According to the characterization results, the activated BP possessed a porous surface and high surface area of 200 m2 g-1, which are important adsorption parameters. Additionally, the removal efficiency for Cr(vi) was evaluated in terms of pH, contact time, initial concentration, and adsorbent dose. Consequently, the optimal operating conditions for removing 94% of Cr(vi) were found to be an adsorption time of 92 min, adsorbent dose of 1.5 g L-1, pH of 3, and initial Cr(vi) concentration of 38 mg L-1. In addition, the adsorption kinetics and isotherms were examined. The pseudo-first-order model with an R2 of 0.996 and the Langmuir isotherm with an R2 of 0.997 were found to be the most effective mathematical representations of the rate and nature of Cr(vi) adsorption on the surface of the activated BP, respectively. Furthermore, it was discovered that the activated BP could be reused six times before its removal efficiency was reduced to less than 70%.

Essential and Potentially Toxic Elements (PTEs) Content in European Tea (Camellia sinensis) Leaves: Risk Assessment for Consumers

Tea (Camellia sinensis) is the second most consumed beverage worldwide, playing a key role in the human diet. Tea is considered a healthy drink, as its consumption has been linked to a lower risk of cardiovascular disease-related events and death, stroke, metabolic syndrome and obesity. However, several studies have shown that C. sinensis is a hyperaccumulator of Al and other elements that are considered potentially toxic. In the present study, the contents of 15 elements (both essential and toxic) were determined for the first time in tea leaves collected in tea gardens located in six different European countries and processed to provide black and green tea. The results showed that Al was the major toxic element detected, followed by Ni, Cr, Pb, As, Cd, Ag, and Hg. Essential elements were detected in the order of Mn, Fe, Zn, Cu, Co, and Se. Statistically significant correlations (p < 0.05) were found in the distribution of some elements, highlighting mechanisms of synergic or antagonist interaction. Multivariate analysis revealed that geographical origin was the main driver in clustering the samples, while the different treatment processes (black or green) did not significantly affect the contents of elements in the leaves. The estimation of potential non-carcinogenic risk revealed no risk for the consumption of European teas for consumers in terms of potentially toxic elements.

Concentration of mineral and heavy metals in raw mare (horse) milk consumed in Yazd, Iran: A risk assessment study

BACKGROUND

In recent years, the mare's milk has been introduced as a rich source of nutrients with hypoallergic characteristics which is widely used for Iranian infants.

OBJECTIVES

The present study aimed to investigate the heavy metal concentration of mare's milk and its consumption risk assessment.

METHODS

About 88 mare's milk was collected from Yazd, the centre of Iran, during the summer of 2020. The raw mare's milk was digested and analysed for mineral and heavy metal content (As, Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, P, Pb and Zn) by ICP-OES. To estimate the health hazard for consumers the Estimated Daily Intake (EDI), Hazard Quotient (HQ) and Hazard Index (HI) of heavy metals were determined.

RESULTS

The Ca ranged from 260.52 to 201.43 mg/L, which was the highest mineral in mare's milk followed by P and Mg. By increasing the age, P and Ca content was increased. The obtained ranges of Cu, Co, Fe, Mn and Zn were 72.12-75.11, 1.12-9.3, 180.69-230.21, 31.24-47.13 and 1060-1200 μg/L, respectively. The Cd and Arsenic content of mares' 8-11 years of age had higher concentrations. The highest Pb content was reported in mares 4-7 years old (10 μg/L). Although, Pb, Cd and As content of the mare's milk was evaluated lower than the permissible limit. Also, the HQ value was As > Cd > Pb > Zn > Ni > Cu for infants, toddlers and adults. The HI of mare's milk was 0.16, 0.15 and 0.022 for infants, toddlers and adults, respectively.

CONCLUSIONS

Mare's milk could be an effective nutrition source for infants and children suffering from milk protein allergies.

Monitoring and evaluating the dietary risk of trace elements content in bottled and hand-shaken tea in Taiwan

Tea is the most frequently consumed beverage worldwide and is obtained from the leaves Camellia sinensis. The traditional way of tea consumption through brewing is gradually being replaced by the consumption of bottled and hand-shaken tea. Despite the different ways of tea consumption, trace elements accumulation and contamination of tea leaves have caused concerns. However, limited studies have reported trace element concentrations in different types of tea in bottled or hand-shaken tea and their health risks. This study aimed to determine the level of trace elements (V, Cr, Co, As, Cd, Pb, Mn, and Zn) in green tea, black tea, and Oolong tea in two varieties of products (bottled and hand-shaken tea). The health risks associated with tea consumption in various age subgroups among Taiwan's general population were also estimated. A Monte Carlo simulation was applied to estimate the distribution of daily trace elements intake through bottled and hand-shaken tea consumption. As to the non-carcinogenic risks, the Monte Carlo simulation showed that hand-shaken green tea had a higher percentage of hazard index (HI) >1 (1.08%~6.05%) among all age groups. As to carcinogenic risks, the Monte Carlo simulation showed that the risks of As exposure from bottled Oolong tea and hand-shaken black, green, and Oolong teas in the 90th percentile in >18 to ≤65 and >65-year-old groups were higher than 10^-6. The current study findings provided some information about trace elements of both bottled and hand-shaken tea and human health risks in the general population of Taiwan.

Transcriptome Analysis Reveals Differentially Expressed Genes Involved in Cadmium and Arsenic Accumulation in Tea Plant (Camellia sinensis)

Tea (Camellia sinensis) is the second most consumed drink in the world. Rapid industrialization has caused various impacts on nature and increased pollution by heavy metals. However, the molecular mechanisms of cadmium (Cd) and arsenic (As) tolerance and accumulation in tea plants are poorly understood. The present study focused on the effects of heavy metals Cd and As on tea plants. Transcriptomic regulation of tea roots after Cd and As exposure was analyzed to explore the candidate genes involved in Cd and As tolerance and accumulation. In total, 2087, 1029, 1707, and 366 differentially expressed genes (DEGs) were obtained in Cd1 (with Cd treatment for 10 days) vs. CK (without Cd treatment), Cd2 (with Cd treatment for 15 days) vs. CK, As1 (with As treatment for 10 days) vs. CK (without Cd treatment), and As2 (with As treatment for 15 days) vs. CK, respectively. Analysis of DEGs showed that a total of 45 DEGs with the same expression patterns were identified in four pairwise comparison groups. One ERF transcription factor (CSS0000647) and six structural genes (CSS0033791, CSS0050491, CSS0001107, CSS0019367, CSS0006162, and CSS0035212) were only increased at 15 d of Cd and As treatments. Using weighted gene co-expression network analysis (WGCNA) revealed that the transcription factor (CSS0000647) was positively correlated with five structural genes (CSS0001107, CSS0019367, CSS0006162, CSS0033791, and CSS0035212). Moreover, one gene (CSS0004428) was significantly upregulated in both Cd and As treatments, suggesting that these genes might play important roles in enhancing the tolerance to Cd and As stresses. These results provide candidate genes to enhance multi-metal tolerance through the genetic engineering technology.

Comparison and Risk Assessment of Macroelements and Trace Metals in Commercial Teas from Different Regions of China

Tea (Camellia sinensis L.) is one of the most widely consumed non-alcoholic beverages worldwide. In the present study, 73 commercial tea samples were collected from tea plantations in the Southwest, South, Jiangnan, and Jiangbei regions of China. The contents of four macroelements (phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)) and 15 trace metals (arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), zinc (Zn), aluminium (Al), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), thorium (Th), thallium (Tl), rubidium (Rb) and barium (Ba)) in tea samples were determined. The mean concentrations of As, Cd, Cr, Hg, Pb, Zn, Al, Cu, Mn, Fe, Ni, Th, Tl, Rb and Ba were in the range of 0.02-0.61, 0.008-0.126, 0.09-1.12, 0.001-0.012, 0.07-1.62, 19.5-73.2, 170-2100, 5.9-43.3, 228-2040, 60-337, 2.09-17.95, 0.002-0.08, 0.004-0.409, 0-150.50 and 3.1-41.2 µg/g, respectively, which were all lower than the maximum permissible limits stipulated by China (NY/T 288-2012, NY 659-2003). The target hazard quotients of each heavy metal were lower than one, and the combined risk hazard index of all heavy metals for adults was in the range of 0.10-0.85; therefore, there was no significant carcinogenic health risks to tea drinking consumers under the current dietary intake. Significant differences were found in the content of trace elements (Zn, Cu, Fe, Ni, Th, Tl, Rb and Ba) (p < 0.05); however, no significant differences were found in the content of macroelements (P, K, Ca and Mg) and trace metals (As, Cd, Cr, Hg, Pb, Al and Mn) in teas from different regions. Therefore, the region did not affect the heavy metal exposure risk. Correlation coefficient and principal component analyses were performed to determine the source of the elements. Three principal factors were obtained: factor 1 was positively related to Ca, Mg, As, Cd, Cr, Hg, Pb, Al, Mn, Fe and Th (32.63%); factor 2 to P, Zn, Cu and Ni (18.64%) and factor 3 to K and Rb (10.10%). Thus, the elements in the same factor might originate from the same source. This study provides an essential basis to understand the variance and potential risks of different elements in tea from different regions of China.

Geochemical characteristics of heavy metals of bedrock, soil, and tea in a metamorphic rock area of Guizhou Province, China

Through field surveys, sampling, and laboratory experiments, the content, enrichment, and migration characteristics of heavy metals in the rock-soil-tea system in the Guizhou metamorphic rock area were analyzed herein. The results show that the As and Hg contents in metamorphic sandstone in the study area are higher than those in slate, while the Mn, Zn, Pb, and Ni contents in slate are higher. The content of heavy metals in the sandstone of the Jialu formation of the Xiajiang group in Neoproterozoic is the highest, and that of the slate of the Fanzhao formation is the lowest. The content of As in the rock samples in the study area is higher than that in the Epicontinental crust, while Cd is found to be deficient. The heavy metals at some soil points exceed the standard, but this does not affect the growth and development of tea. The content of heavy metals in most tea is lower than the safety limit standards, and the THQ value is less than 1, indicating that the heavy metals in tea in Guizhou metamorphic rock areas pose no concern for human health. In the metamorphic rock distribution areas of Guizhou, tea does not enrich As, Cr, Hg, and Pb in soil, but enriches Mn, Cu, Ni, and Zn to varying degrees, with the enrichment of Mn being the strongest.

Health Risk Assessment of Exposure to Trace Elements from Drinking Black and Green Tea Marketed in Three Countries

Although tea can be beneficial for our health, consuming excess trace elements in tea can be harmful. In this study, the carcinogenic and noncarcinogenic health risk for trace elements in tea influenced by the country of origin, tea type, and infusion process was assessed. Tea (Camellia sinensis) purchased from China, India, and the USA, including black and green tea, were analyzed for essential micronutrients (Cu, Se, and Zn) and nonessential trace elements (Ag, As, Ba, Cd, Cr, and Pb) in leaves and three types of infusions. The results showed that country of origin, tea type, and infusion process had a significant influence on the trace element contents in tea leaves and infusions, also on health risk. Country of origin had a significant influence on Ba, Cr, Pb, and Zn contents in tea leaves and on As, Ba, Cd, Cr, Pb, and Zn contents in tea infusions. Black tea had significantly higher (p < 0.05) Cr and Cu content in tea leaves than green tea, but only Cr content was significantly higher (p < 0.05) than that of green tea in tea infusion. The trace element contents were the highest in the first infusion and decreased as the number of infusion steps increased. The results showed that the consumption of tea infusion was not likely to cause noncarcinogenic risk. However, the carcinogenic risk for As was of concern. Our results indicate that avoiding drinking the first infusion can help to reduce both carcinogenic and noncarcinogenic health risks for trace elements.

Concentrations, leachability, and health risks of mercury in green tea from major production areas in China

Green tea has many health benefits and is the most consumed type in China. However, the heavy metals and contaminants in tea can also pose a great risk to human health. In this study, mercury (Hg) concentration in green tea collected from 11 provinces in China was examined. The leaching characteristics of Hg during brewing and the associated exposure to drinkers were also evaluated. Results indicated a low potential of Hg accumulation in green tea. The Hg content of green tea from Wanshan District, Guizhou Province-which has the largest Hg mine in China and is severely contaminated by Hg-could be limited by controlling the harvest time of tea leaves. The average Hg content of green tea from 43 tea production sites in China was only 6.3 ± 6.4 µg/kg dry weight. The brewing experiments of green tea showed that the leaching ratio of Hg was 22.61 ± 7.58% for 40 min of a single brew, and increased to 32.83 ± 12.37% after four rounds (3 min/ round) of brewing. The leaching of Hg from tea leaves was significantly affected by leaching time, temperature, and solid-liquid ratio but not by water hardness. The risk of Hg exposure from green tea intake was found to be very low, with an average hazard quotient (HQ) value of only 1.82 ± 1.85% for a single brew in 40 min and 2.64 ± 2.68% after four rounds of brewing. However, in some highly contaminated areas, with HQ values as high as 43.12 ± 2.41%, green tea intake may still pose a high risk of Hg exposure, and this risk should not be ignored.

Detection of Changes in Total Antioxidant Capacity, the Content of Polyphenols, Caffeine, and Heavy Metals of Teas in Relation to Their Origin and Fermentation

Tea (Camellia sinensis) is widely sought for beverages worldwide. Heavy metals are often the main aims of the survey of teas, given that the use of agricultural fertilization is very frequent. Some of these may affect the content of bioactive compounds. Therefore, in this study, we analyzed fermented and non-fermented teas of a single plant origin from Japan, Nepal, Korea, and China, and described mutual correlations and changes in the total antioxidant capacity (TAC), and the content of polyphenols (TPC), caffeine, and heavy metals in tea leaves, in relation to the origin and fermentation process. Using UV-VIS spectrophotometry and HPLC-DAD, we determined variations in bioactive compounds’ content in relation to the fermentation process and origin and observed negative correlations between TAC and TPC. Heavy metal content followed this order: Mn > Fe > Cu > Zn > Ni > Cr > Pb > Co > Cd > Hg. Given the homogenous content of these elements in relation to fermentation, this paper also describes the possibility of using heavy metals as determinants of geographical origin. Linear Discriminant Analysis showed an accuracy of 75% for Ni, Co, Cd, Hg, and Pb, explaining 95.19% of the variability between geographical regions.

The chemical composition and heavy metal content of sesame oil produced by different methods: A risk assessment study

The oil was extracted from sesame seed with two extraction methods. Traditional (Ardeh oil) and industrial method (cold pressing method: virgin and refined sesame oil) oil extraction was studied to compare the quality and heavy metal content of extracted oils. The chemical properties (fatty acid composition, peroxide, anisidine, acid values, and TOTOX) and heavy metal contents were investigated. The Hazard Quotient (HQ) and Hazard Index (HI) of heavy metal intakes were calculated. The results demonstrated that the predominant fatty acid in oil samples was oleic, linoleic, palmitic, and stearic acids. It was indicated the peroxide, anisidine, acid values, and TOTOX of oil samples were as the order of Ardeh oil > virgin sesame oil > refined sesame oil. The reduction pattern of Pb > Zn >Cu > Cd >As was reported in sesame seed. Although the oil refining had been greatly reduced the Pb of oil sample, but it had yet been much higher than the permissible levels set by Codex Alimentarius. The HQ and HI of all heavy metals were less than one, but they were higher in Ardeh oil compared to others. It is necessary to monitor the presence of heavy metal contaminants and the quality of imported sesame seeds prior to oil preparation.

Distribution, accumulation, and potential risks of heavy metals in soil and tea leaves from geologically different plantations

Risk assessment regarding heavy metals in tea is crucial to ensure the health of tea customers. However, the effects of geological difference on distribution of heavy metals in soils and their accumulation in tea leaves remain unclear. This study aimed to estimate the impacts of geological difference on distribution of cadmium (Cd), lead (Pb), thallium (Tl), mercury (Hg), arsenic (As), antimony (Sb), chromium (Cr), nickel (Ni), and manganese (Mn) in soils and their accumulation in tea leaves, and further evaluate their health risks. 22 soils and corresponding young tea leaves (YTL) and old tea leaves (OTL), from geologically different plantations, were sampled and analyzed. Results showed that heavy metals concentrations in soils, derived from Permian limestone and Cambrian weakly mineralized dolomite, were obviously greater than those from Silurian clastic rock. The geological difference controlled the distribution of soil heavy metals to a large extent. Contents of Cd, Tl, and Mn in tea leaves mainly depended on their contents in soils. Soil Hg, Pb, As, and Sb contents may not be the only influencing factors for their respective accumulation in tea leaves. More attentions should be paid to soil acidification of tea plantations to ensure the tea quality security. Target hazard quotients (THQ) of Cd, Pb, Tl, Hg, As, Sb, Cr, and Ni and hazard index (HI) via tea intake were below one, indicating no human health risk. The non-mineralized Silurian area was less at risk of heavy metals accumulation in tea leaves than the Cambrian metallogenic belt and the Permian Cd-enriched zone. This study could provide an important basis to understand and mitigate the potential risks of heavy metals in tea.