Toxicological Distribution of Mercury Concentrations in Abiotic and Biotic Environments: A Systematic Review and Meta-Analysis

Abstract

Background: Mercury (Hg), particularly methyl-mercury (Methyl-Hg), is a potentially dangerous heavy metal with special physicochemical features including environmentally persistent, bio-accumulative, bio-concentrated, and bio-magnification. Thus, it can potentially be a high risk to both human and environmental health. However, there are few studies quantifying mercury toxicity in all environmental components, especially in developing countries.  Therefore, this systematic review and meta-analysis aimed to determine the amount of mercury present in various environmental components.   

Methods: Preferred Reporting Items for Systematic Reviews (PRISMA) updated criteria were used for the flow diagram. PubMed, Medline, Web of Science, Embase, previous reviews, reports, and other methods were searched as databases. A thorough search was conducted for all studies published in 2000–2023 using keywords and MeSH terms with Boolean logic operators (AND, OR). The titles and abstracts returned by the search were screened. Data were extracted using a prescribed Microsoft Excel. The mean concentration of Hg in soil, blood, fish and dust, and plant leaf was estimated using STATA version 17. The random effect model with a 95% confidence interval was used at a p-value of less than 0.05.

Results: A total of 208 records were searched from PubMed (n = 33), Medline (n = 39), Web of Science (n = 37), Embase (n = 23), previous reviews (n = 18), reports (n = 5) and via other methods (n = 53). This review revealed that different concentrations of Mercury (Hg) are found in various components of the environment.  This review found the mean mercury concentration in fish was 1.60 µg (95% CI: -0.02, 3.22 µg), soil 0.32mg/kg (95% CI: -1.25, 1.90mg/km), dust 0.47 mg/kg (95% CI: -1.10, 2.04mg/km), water bodies 0.55 µg/dm3 (95% CI: -1.04, 2.13), plant 28.96 mg/kg (95% CI: -22.57, 80.49 mg/kg), and human blood at 0.92 µg/L (95% CI: -0.72 µg/L, 2.57).

Conclusions: This systematic review and meta-analysis concluded that the methyl-mercury form is the most prevalent in both biotic and abiotic as compared to other forms of mercury. Nevertheless, limited research has been found in low- and middle-income nations, where the majority of raw mercury is produced. Moreover, the review suggested that international cooperation, national policies, and regulations on mercury management are crucial for minimizing the harmful effects of both biotic and abiotic mercury components.