Iran Occupational Health

  Background and aims

  Dentists are occupationally exposed to elemental mercury from placements of mercury-containing amalgam. Although many studies have been conducted on mercury intoxication, there is still widespread concern about possible ill effects of chronic low-level mercury exposure on dentists. The present study examined the effects of occupational exposure to low levels of mercury by a group of dentists.

  Methods

  In this historical cohort study, subjects consisted of 106 dentists and 94 general practitioners (referent group), from private and public clinics in Shiraz city. Subjects were requested to complete a questionnaire on demographic variables, symptoms experienced and work practices. Additionally, using standard methods, atmospheric and urinary concentrations of mercury were measured. The data were analyzed by appropriate statistical tests. In univariat analysis, Chi-Square test was used to compare the prevalence of symptoms among both groups. Independent sample t-test and Mann-Whitney’s U-test were used to compare the mean and median of quantitative data of both groups. Multivariate logistic regression analysis was used to adjust for potential confounders.

  Results

  Both groups were similar as far as most demographic and socioeconomic variables, but age and number of personal amalgam fillings, were concerned. Median of atmospheric concentration of mercury was found to be 3.35 μg/m³. Likewise, the urinary concentration of mercury in dentists was estimated to be 3.22 μg /g.creatinine. This value was significantly higher than that of the referent group. Additionally, analysis of the data revealed that subclinical symptoms of intoxication were more prevalent in dentists.

  Conclusion

 Our findings indicate that occupational exposure to mercury by dentists, even at low levels, is associated with a significant increase in the prevalence of subclinical symptoms of intoxication.