Passive and active sampling of occupational exposures to nitrous oxide among Indian health service dental employees and possible mitigating factors
Creators: name: Hansen, John
name: Juarez, Theodore
name: Brueggemeyer, Mary
name: Majar, Maria
name: Woodlee, Charles
Publisher: name: F1000Research
Year: 2017

description: Nitrous oxide is a commonly used gas in dental facilities and considered safe for patients undergoing dental procedures. However, epidemiological studies show that there are adverse health effects associated with chronic occupational exposure to nitrous oxide, including reproductive issues, neurologic, renal and liver disease. Indian Health Service reports have documented high levels of nitrous oxide during dental procedures. This study compared sampling using the Thermo Scientific Miran SapphIRe portable analyzer with the Advanced Chemical Sensor™ Passive Badge, and characterized dental personnel’s exposure to nitrous oxide levels in the breathing zones during dental procedures.<br><br>Similar exposure groups were determined by job title (Dentist and Dental Assistant) and an ANOVA was used to explore the appropriateness of considering similarity of the groups across 6 dental clinics within the Indian Health Service. An independent t- test was used to determine if there was a mean difference of exposure between the similar exposed groups. A paired t-test was used to compare the similarity of the two sampling methods, and the Bland-Altman analysis was used to assess level of agreement between the two methods. Finally, this study looked at the effect of nitrous oxide concentration/flow rate and room air exchange rates on exposure levels.<br><br>Excursion levels over the occupational exposure limit of 250 ppmv were exceeded in 21 of 41 (51%) procedures in this study. Mean upper tolerance limit estimates for dental procedures were 1245 ppmv for dentists and 802 ppmv for dental assistants. Four passive 8-hour TLV-TWAs were over the 50 ppmv occupational exposure limit, two for dentists (55.6 and 152 ppmv) and two for dental assistant (81.3 and 56.0 ppmv).<br><br>There was no significant difference between similar exposure group concentrations using either sampling method (Miran SapphIRe portable analyzer, 0.071; Advanced Chemical Sensor™ Passive Badge, p-value 0.106). However, both sampling methods showed a trend toward the dentist having an 81 to 86% higher exposure rate than the dental assistant.<br><br>When comparing sampling methods by job title, the dentist exposure group showed no difference (p-value of 0.058) while the dental assistant exposure group showed a difference (p-value of 0.019). Bland-Altman analysis showed that both sampling methods differed by more than 25% with 95% confidence when compared to each other.<br><br>The effect of nitrous oxide concentration and flow rate, and room air exchange rate did not show any significant association with observed nitrous oxide concentrations in the breathing zones of employees.<br><br>This study suggests there needs to be a focus to better control excursions above 250 ppmv, which would also help lower procedural and 8-hour TLV-TWAs. Continued sampling should be conducted to increase sample size and overall power to better characterize similar exposure groups. Lastly, laboratory studies designed to understand the difference in sampling methods should be accomplished.