A systematic Review and Meta-Analysis of Mercury Concentrations in Blood, Urine, and Area Air Samples among Dentists in Iran

Background and Dentists are constantly exposed to mercury vapor and its role in the development of many chronic diseases has been proven. Therefore, this study aims to determine the mean concentrations of mercury in samples of blood, urine and area air among Iranian dentists.
This study was conducted based on PRISMA guidelines. Two authors searched Persian and English online databases including Magiran, Iranmedex, SID, Medlib, Scopus, PubMed, Science Direct, Cochrane, Web of Science and the Google Scholar search engine without time limit until 2016. To evaluate the heterogeneity of the studies, Cochran's Q test and I2 index were used. Data were analyzed using Stata 11.1 software based on random effects model.
12 studies with a sample size of 1,276 dentists were reviewed. The mean concentration of mercury in samples of blood, urine and area air was estimated to be 1.21 μg/dl (95% CI [confidence interval]: 0.67 to 1.75), 5.54 μg/l (95% CI: 4.03 to 7.06) and 7.58 μg/m3 (95% CI: 2.56 to 12.60), respectively. The standardized mean difference in the mercury concentration was 1.75 μg/dl (95% CI: -0.05 to 3.55) in blood and 1.79 μg/dl (95% CI: -1.40 to 4.99) in urine between the case and control groups (P>0.05).
The results of this study demonstrated that the 95% CI of the mean concentration of mercury in the urine samples of Iranian dentists is higher than the standard limit. Therefore, Iranian dentists should be examined annually in terms of urinary mercury concentration.