Investigation of heavy metals in mint plants irrigated by wastewater: a systematic review and meta-analysis

Nowadays, water shortage crisis leads to wastewater reuse in agriculture sector. The presence of pollutants such as heavy metal in wastewater results in the accumulation of them in vegetables, and it will finally be transferred to consumers and will have irreversible effects on their health. Therefore, the present study was performed to do a systematic review along with meta-analysis on heavy metal accumulation in mint plant that is irrigated with wastewater.

Related articles were collected from databases like SID, Magiran, Iranmedex, IranDoc, Embase, Medline, PubMed, Web of Science, Scopus, and Google scholar between 1982 and 2019 and the required data were extracted. Then, due to the heterogeneity of studies entered in the research, a random effect model was applied to analyze them using STATA 14 software. Non-carcinogenic risk was assessed for children and adults.

According to the search results, 1693 articles were entered in the review process until the beginning of 2019 and finally only 12 articles were included in the research. According to the results of the meta-analysis, the order of the metals based on concentration (mg/kg) were: Zn > Ni > Cr > Cu > Pb > Cd. Also, based on the non-carcinogenic risk assessment results, mint consumption showed a significant health effects on children age group compared to adults, especially in India and Pakistan. 

wastewater reuse in agriculture sector leads to increase concentration of metals in vegetables like mint. This increased the risk of non-carcinogenicity in the age groups, especially children. Therefore, it is recommended that continuous monitoring of irrigation sources, soils, and vegetables is done to prevent the transmission of these pollutants to the human food cycle.