Passive dosimetry of dental hygienists' exposure to nitrous oxide

This study is the first to measure exposure to waste nitrous oxide (N2O) in the dental work setting in a broad geographical region (25 states), with passive dosimeters, and for dental hygienists. Thirty-five dental hygienists who reported that they administered N2O and 20 dental hygienists who reported that they never administered N2O constituted the sample. The former (n = 35) received both a 40-hr dosimeter, which measured exposure during administration of N2O, and a 168-hr dosimeter, which measured exposure during all work hours. The latter (n = 20) received only the 168-hr dosimeter. Exposure was measured during 2 wk in April 1990. For all work hours, the mean ppm-hr was 3,636 and the mean time-weighted average (TWA) was 78 ppm. The corresponding means during administration were 2,754 ppm-hr and 842 ppm TWA. The data for dental hygienists with passive dosimeters were similar to previously reported findings for dentists as measured by infrared spectrophotometry and gas chromatography. Hygienists who worked in dental settings with scavenging equipment received higher average levels of exposure to N2O than did hygienists who worked in settings without scavenging.