The Concentration of Lead, Cadmium, Copper, Nickel, Zinc, Manganese and Iron in Saffron: A Meta-analysis and Systematic Review

Abstract

Background: We aimed to investigate the concentrations of metals, including lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), iron (Fe), zinc (Zn), and manganese (Mn), in various types of saffron. Methods: All published studies until 2022 were searched from PubMed, Scopus and Web of Science databases. The published articles’ references were also evaluated to investigate the prevalence of heavy metal contamination in different types of saffron. The heterogeneity and concentration were estimated using I2 and the random effect model, respectively. Results: Among 128 articles retrieved in the identification phase, eight articles were included in this meta-analysis. The Pb exhibited the highest concentration among metals, with an average concentration of 0.10 mg/kg and a range of 0.11-0.10 mg/kg. Cd had the lowest concentration, with an average of 0.009 mg/kg and a range of 0.008-0.010 mg/kg. The concentration of Ni, Fe, Zn, Mn, and Cu were also in accordance with the sequence of Ni>Fe>Zn>Mn>Cu. Specifically, Ni demonstrated the highest concentration among essential metals in the sample, with an average of 2.81 mg/kg and a range of 2.76-2.86 mg/kg, while Cd displayed the lowest concentration, with an average of 0.022 mg/kg and a range of 0.023-0.023 mg/kg. Conclusion: The concentration of different metals in the examined saffron was variable, which can be attributed to several factors, including characteristics of the metals, nature of the saffron plant, composition of the irrigation water and the soil used for production of the plant, water conditions and crop cultivation.