THE EFFECT OF OCCUPATIONAL EXPOSURE TO MERCURY-VAPOR ON THE FERTILITYOF FEMALE DENTAL ASSISTANTS

Exposure to mercury vapour or inorganic mercury compounds can impair f ertility in laboratory animals. To study the effects of mercury vapour on fertility in women, eligibility questionnaires were sent to 7000 r egistered dental assistants in California. The final eligible sample o f 418 women, who had become pregnant during the previous four years, w ere interviewed by telephone. Detailed information was collected on me rcury handling practices and the number of menstrual cycles without co ntraception it had taken them to become pregnant. Dental assistants no t working with amalgam served as unexposed controls. Women with high o ccupational exposure to mercury were less fertile than unexposed contr ols. The fecundability (probability of conception each menstrual cycle ) of women who prepared 30 or more amalgams per week and who had five or more poor mercury hygiene factors was only 63% of that for unexpose d women (95% CI 42%-96%) after controlling for covariates. Women with low exposure were more fertile, however, than unexposed controls. Poss ible explanations for the U shaped dose response and limitations of th e exposure measure are discussed. Further investigation is needed that uses biological measures of mercury exposure.