a systematic review on exposure to toxic and essential elements through black tea consumption in iran: could it be a major risk for human health?

background: tea is the most popular nonalcoholic beverage worldwide. in recent years, some iranian studies have shown the occurrence of toxic elements in fresh or dried tealeaves as well as in brewed tea. the present study aimed to ascertain the health risks associated with exposure to toxic and essential element through black tea consumption in iran by systematically reviewing the accredited articles in the field. methods: in order to obtain the relevant articles and academic databases, the search engines covering the specifi c disciplines were searched for the keywords, including tea, elements, heavy metals and determination. having provided the complete list of sound articles, being conducted in iran was considered as the inclusion criteria. exclusion criteria were established as failure to provide information on the validity parameters and accuracy in the analytical methods. choosing well conducted, reliable studies, analytical results for the concentration of each element in black tea were utilized in the determination of the hazard quotient (hq) for the given element and the hazard index (hi) was then determined for all of the elements in each study. results: among the total studies, two were considered to be reliable. aluminum was found to be the most abundant element in black tea marketed in iran. although the hq for manganese was the highest among the studied elements, hq and hi values for both toxic elements and essential elements were calculated as less than 1. conclusions: the hazard of excessive element intake through black tea consumption should be considered as negligible in iran. however, related risk for manganese appeared to be more than toxic metals.