Mercury exposure of a female dentist before pregnancy

A 30-year-old female dentist was exposed to mercury vapour from a leaking amalgamator for approximately one year. No toxic effect was noted. During and after the exposure urine samples were regularly taken for mercury analysis. The highest value during this period was 60 micrograms Hg/l urine (expressed in micrograms/g creatinine: 42; the normal value for unexposed persons is a few micrograms/g creatinine). The mercury concentration in air was at most 840 micrograms/m3 at the amalgamator (threshold limit for occupational exposure: 50 micrograms/m3). The dentist became pregnant and during pregnancy her average urine mercury concentration was 18 micrograms/g creatinine. Ultrasound examination of the fetus at 20 weeks of gestation showed a mild bilateral hydronephrosis. At 32 weeks of gestation the hydronephrosis had resolved. The dentist gave birth to a normal-weight baby boy, who, at the time of writing, is 2 years of age and appears clinically healthy.