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Policy on Minimizing Occupational Health Hazards Associated with Nitrous Oxide

Purpose

The American Academy of Pediatric Dentistry (AAPD) recognizes that exposure to ambient nitrous oxide (N2O) may be an occupational health hazard for dental personnel and encourages practitioners to take all precautions to minimize associated risks.

Methods

This policy was developed by the Clinical Affairs Committee and adopted in 1987. This document is a revision of the previous version, revised in 2013. The update used electronic database and hand searches of articles in the medical and dental literature using the following parameters: terms: nitrous oxide, occupational exposure, AND dentistry; fields: all; limits: within the last 10 years, English. Additionally, guidelines and recommendations from the National Institute for Occupational Safety and Health (NIOSH) were reviewed.1-2  Expert opinions and best current practices were relied upon when sufficient scientific data were not available.

Background

Effects of occupational exposure to ambient N2O are uncertain, especially since the introduction of methods to scavenge N2O and ventilate operatories.3  As of 2008, there were no definitive studies linking general health problems and reproductive difficulties among dental personnel to chronic exposure to scavenged ambient N2O.3  A maximum safe level of ambient N2O in the dental environment has not been determined.4-6 

Reduction of ambient N2O through system maintenance, scavenging, ventilation, use of the minimal effective dose, and patient management is important to maintaining the lowest practical levels in the dental environment.1,2,7  Frequent and regular inspection and maintenance of the N2O delivery system, together with the use of a scavenging system, can reduce ambient N2O significantly.8 Using a well-fitted mask and an appropriate suction strength via the scavenging system will minimize leakage, reducing ambient N2O levels.8,9  The use of a double-mask patient delivery system also has been shown to be more effective than a single-mask system in the removal of waste nitrous oxide.10,11  The combined use of the double mask system and scavenging systems with a high evacuation flow rate have been demonstrated to decrease occupational exposure to nitrous.12  NIOSH has recommended that the exhaust ventilation of N2O from the patient’s mask be maintained at an air flow rate of 45 L/min and vented outside the building away from fresh air intakes.1,5  However, scavenging at this rate has been shown to reduce the level of psychosedation achieved with N2O inhalation.13  Where possible, outdoor air should be used for dental operatory ventilation.1,14  Supply and exhaust vents should be well separated to allow good mixing and prevent short-circuiting.1  Female dental staff frequently (i.e., three or more days a week) exposed to nitrous oxide have been found to have no elevated risk of spontaneous abortion in offices using appropriate scavenging systems.15,16 

Patient selection is an important consideration in reducing ambient N2O levels.7  Patients who are unwilling or unable to tolerate the nasal hood and those with medical conditions (e.g., obstructive respiratory diseases, emotional disturbances, drug dependencies) that contraindicate the use of N2O should be managed by other behavior guidance techniques.7  In the dental environment, patient behaviors such as talking, crying, and moving have been shown to result in significant increases in baseline ambient N2O levels despite the use of the masktype scavenging systems.17,18  Utilization of titrated nitrous concentration levels in relation to procedure difficulty should be considered. Nitrous can be discontinued once adequate anesthesia is achieved,19 or decreased levels can be maintained during easier procedures and increased for stimulating procedures.5

The use of scavenging systems alone cannot lower the ambient N2O levels to the recommended standards.8,17,20  Use of supplemental measures, such as high-volume dental suction placed in proximity to the dental operative site, has been shown to reduce ambient N2O levels significantly.17,21  Diligent use of the above practices in the pediatric dental environment has allowed for the reduction of ambient N2O to the levels recommended by NIOSH.21,22  Measurement of N2O levels in the dental operatory can be helpful in determining the type and extent of remediation necessary to decrease occupational exposure.

Policy Statement

The AAPD encourages dentists and dental auxiliaries to maintain the lowest practical levels of N2O in the dental environment while using N2O. Adherence to the recommendations below can help minimize occupational exposure to N2O.

  • Educate dental personnel on minimizaing occupational exposure to and potential abuse of nitrous oxide.
  • Use scavenging systems that remove N2O during patient’s exhalation.
  • Ensure that exhaust systems adequately vent scavenged air and gases to the outside of the building and away from fresh air intake vents.
  • Use, where possible, outdoor air for dental operatory ventilation.
  • Implement careful, regular inspection and maintenance of the nitrous oxide/oxygen delivery equipment.
  • Carefully consider patient selection criteria (i.e., indications and contraindications) prior to administering N2O.
  • Select a properly-fitted mask size for each patient.
  • During administration, visually monitor the patient and titrate the flow/percentage to the minimal effective dose of N2O.
  • Encourage patients to minimize talking and mouth breathing during N2O administration.
  • Use high volume dental suction when possible during N2O administration.
  • Administer 100 percent oxygen to the patient for at least five minutes after terminating nitrous oxide use to replace the N2O in the gas delivery system.

References

  1. National Institute of Occupational Safety and Health. Control of nitrous oxide in dental operatories. Appl Occup Environ Hyg 1999;14(4):218-20.
  2. National Institute of Occupational Safety and Health. Controlling exposures of nitrous oxide during anesthetic administration. Cincinnati, Ohio: National Institute of Occupational Safety and Health; 1994. DHHS/NIOSH Publication No. 94-100.
  3. Sanders RD, Weimann J, Maze M. Biologic effects of nitrous oxide. Anesthesiology 2008;109(4):707-22.
  4. Howard WR. Nitrous oxide in the dental environment: Assessing the risk and reducing the exposure. J Am Dent Assoc 1997;128(3):356-60.
  5. American Dental Association Council on Scientific Affairs, American Dental Association Council on Dental Practice. Nitrous oxide in the dental office. J Am Dent Assoc 1997;128(3):364-5. 
  6. Donaldson D, Meechan JG. The hazards of chronic exposure to nitrous oxide: An update. Br Dent J 1995;178 (3):95-100.
  7. American Academy of Pediatric Dentistry. Use of nitrous oxide for pediatric dental patients. Pediatr Dent 2018;40(6):281-6. 
  8. Rademaker AM, McGlothlin JD, Moenning E, Bagnoli M, Carlson G, Griffin C. Evaluation of two nitrous oxide scavenging systems using infrared thermography to visualize and control emissions. J Am Dent Assoc 2009;140(2):190-9.
  9. Crouch KG, Johnston OE. Nitrous oxide control in the dental operatory: Auxiliary exhaust and mask leakage, design, and scavenging flow rate as factors. Am Ind Hyg Assoc J 1996;57(3):272-8. 
  10. Chrysikopoulou A, Matheson P, Miles M, Shey Z, Houpt M. Effectiveness of two nitrous oxide scavenging nasal hoods during routine pediatric dental treatment. Ped Dent 2006;28(3):242-7.
  11. Freilich MM, Alexander L, Sandor GKB, Judd P. Effectiveness of 2 scavenger mask systems for reducing exposure to nitrous oxide in a hospital-based pediatric dental clinic: A pilot study. J Can Dent Assoc 2007;73(7):615-615d.
  12. Messeri A, Amore E, Dugheri S, et al. Occupational exposure to nitrous oxide during procedural pain control in children: A comparison of different inhalation techniques and scavaging systems. Pediatr Anaesth 2016;26(1):919-25.
  13. Primosch R, McLellan M, Jerrell G, Venezie R. Effect of scavenging on the psychomotor and cognitive function of subjects sedated with nitrous oxide and oxygen inhalation. Pediatr Dent 1997;19(8):480-3.
  14. Centers for Disease Control and Prevention. Control of nitrous oxide in dental operatories. 2014. Available at: “https://www.cdc.gov/niosh/docs/hazardcontrol/hc3.html”. Accessed May 31, 2018. Archived by WebCite® at: “http://www.webcitation.org/71NbEfa74”) 
  15. Rowland AS, Baird DD, Shore DL, et al. Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide. N Engl J Med 1992;327(14):993-7.
  16. Rowland AS, Baird DD, Shore DL, Weinberg CR, Savitz DA, Wilcox AJ. Nitrous oxide and spontaneous abortion in female dental assistants. Am J Epidemiol 1995;141(6):531-7.
  17. Henry RJ, Primosch RE, Courts FJ. The effects of various dental procedures and patient behaviors upon nitrous oxide scavenger effectiveness. Pediatr Dent 1992;14(1):19-25. 
  18. Crouch KG, McGlothin JD, Johnston OE. A long-term study of the development of N2 O controls at a pediatric dental facility. Am Ind Hyg Assoc J 2000;61(5):753-6. 
  19. Guelmann M, Brackett R, Beavers N, Primosch RE. Effect of continuous versus interrupted administration of nitrous oxide-oxygen inhalation on behavior of anxious pediatric dental patients: A pilot study. J Clin Pediatr Dent 2012;37(1):77-82. 
  20. Gilchrist F, Whitters CJ, Cairns AM, Simpson M, Hosey MT. Exposure to nitrous oxide in a paediatric dental unit. Int J Paediatr Dent 2007;17(2):116-22. 
  21. Henry RJ, Borganelli GN. High-volume aspiration as a supplemental scavenging method for reducing ambient nitrous oxide levels in the operatory: A laboratory study. Int J Paediatr Dent 1995;5(2):157-61. 
  22. Borganelli GN, Primosch RE, Henry RJ. Operatory ventilation and scavenger evacuation rate influence on ambient nitrous oxide levels. J Dent Res 1993;72(9):1275-8.