A pilot study to determine mercury exposure through vapor and bound to PM10 in a dental school environment

Mercury (Hg) is widely used in the dental working environment, exposing dental practitioners and assistants to potentially toxic Hg vapors. Concentrations of Hg in vapor and in particulate matter (PM10) were measured in the Dental Simulation Laboratory (DSL) and in the Dental Clinic (DC) at the School of Dentistry, University of Puerto Rico. PM10 samples were collected over a 36-h period and Hg vapor was collected for eight-hour periods. PM10 mass was determined gravimetically and Hg (bound to PM10 and vapor) was extracted and analyzed by atomic absorption. Indoor levels of PM10 in the DSL ranged from 9.2 to 41.6 microg/m3 and 35.0 to 68.2 microg/m3 in the DC. Levels of particle-bound Hg ranged from 0.1 to 1.2 microg/m3 and in vapor 1.1 to 3.3mg/m3 at the DSL; the DC levels ranged from <0.01 to 0.2 microg/m3 for particle bound Hg and 13.6 to 102.7 microg/m3 in vapor. PM10 concentrations were below Indoor Air Quality suggested limits for total dust (100 microg/m3). Levels of mercury bound to PM10 were low; however, mercury vapor was several times higher than the suggested OSHA (permissible exposure limit--100 microg/m3) in the DSL.