Evaluation of environmental and occupational exposure to mercury among Iranian dentists.

The purpose of the study was to evaluate the environmental and occupational exposure to mercury (Hg), and to examine the various parameters, which contribute to high levels of mercury of Iranian dentists in Tehran. One-hundred hair and nail samples were collected from dentists. In addition, fifty samples from a control group and twenty-five additional samples from dental nurses were taken for comparison. The survey included a structured questionnaire designed to provide information about the parameters that influenced their occupational and environmental exposure to Hg. Overall mean concentrations in the hair and nails of the dentists was 2.84+/-0.47 and 3.56+/-0.53 mg/kg dry wt respectively. The equivalent values were 0.61+/-0.07 mg/kg in hair and 0.39+/-0.06 mg/kg in nails for the control group. In addition, mean concentrations in the dental nurses were 0.92+/-0.23 and 1.77+/-0.51 mg/kg in hair and nails respectively. The study showed that use of masks had a significant effect on Hg levels (p=0.02 for hair and p=0.03 for nails) and use of gloves only had significant effect on nails Hg (p=0.05). Hg concentrations in nails were significantly lower among the dentists who always used gloves and masks. Also, fish consumption and number of patients visited per day had a significant effect on hair (p=0.02 and p=0.02 respectively) and nails (p=0.03 and p=0.02 respectively) Hg. On the other hand, there was a significant effect of age in relation to Hg concentration in the hair and nails of the dentists (p=0.006 for hair and p=0.01 for nails). Multiple regressions were computed between hair Hg and the various assessed variables. The only positive results were between Hg concentration and masks for the dentists (p=0.03), and Hg concentration and the number of fish meals for the control group (p=0.009).