Editorial
THICKENING VAPORS Nitrous oxide may soon be joining the ranks of the unemployed. An article by Allen, in this issue of our JournaL summarizes some of the attempts to control the levels of nitrous oxide pollution found in dental operatories. Based on a survey of anesthetic health hazards among dentists1 using hospital dental operating rooms, it was found that there was a significant increase in spontaneous abortions (78%) in the spouses of exposed dentists. Congenital abnormality rates appeared to be slightly higher (15%) in this same exposed group. The rate of cancer in the exposed group was also higher (35%). Because of the small sample size, these latter two determinations were not statistically significant. The incidence of liver disease was found to be increased 156% in the exposed group compared with the unexposed control. This difference was highly significant. Of course, this operating room study could not isolate nitrous oxide as the likely offending agent, hence other studies of dental operatories where nitrous oxide is the only inhalational agent were advised. Dr. Edward Driscoll Chief, Anesthesiology Section of the National Institute of Dental Research, serving as a pro tem chairman of a special committee of the American Society of Oral Surgeons, the American Dental Association and the American Dental Society of Anesthesiology, convened a meeting in Washington to plan further study of this proW lem. Members in attendance included, among others, Mr. Philip Bierbaum, a representative of the National Institute of Occupational Safety and Health (NIOSH) of H.E.W.; Dr. Charles Witcher of Stanford University's Department of Anesthesiology, where much of the investigational work is being performed.
Published studies by Millard and Corbett2 where concentrations of nitrous oxide
1. Cohen, E. N., Brown, B. W., Bruce, D. L., Cascorbi H. F., Corbett, T. F., Jones, T. W., Witcher, C. E. A survey of anesthetic health hazard among dentists. J Am Dental Assoc. 90:1291-1296, 1975. 2. Millard, R. I., Corbett, T. H. Nitrous oxide concentrations in the dental operatory. J Oral Surg 32:593-594, 1974.
3. Witcher, C., Piziali, R., Sher, R., Moffat, R. J. Development and evaluation of methods for the elimination of waste anesthetic gases and vapors in hospitals. U.S. Dept. of Heath, Education and Welfare, National Insfitute of Occupational Safety and Health Division of Field Studies and Clinical Investigations, Cincinnati, Ohio. May 1975.
JANUARY-FEBRUARY, 1976
5
found in the dental operatory during conscious sedation exceeded hospital operating room levels were cited. Newer unpublished data showing as much as 5000 parts per million (ppm) of N20 in the unprotected dental operatory were presented. NIOSH published a report by Witcher et al. entitled "Development and Evaluation of Methods For the Elimination of Waste Anesthetic Gases and Vapors in Hospitals"3 recommending a maxmum "safe" concentration of only 30 ppm. With the aid of specific modifications of equipment and facilities, it has been possible to reduce dental operatory nitrous oxide concentration to these "safer" levels. Much of this work was carried on by Stanford researchers in cooperation with Dr. Donald Zimmerman. Some of the measures recommended to achieve lowered levels of pollution in the dental office are rather simple: They require scavenging waste gases, equipment maintenance to reduce gas leakage, lower flow rates for sedation and anesthesia cases, improved circulation of room air to prevent build-up of waste gases around the heads of the patient and professional personnel and the incorporation of a new double system inhalation-evacuation nasal mask. Periodic air monitoring is also advised.
"Dentists considering the purchase of scavenging equipment are urged to insist on appropriate documentation that the equipment is actually effective in controlling N20 exposure of personnel and not apt to disturb the anesthetic mixture," advises Dr. Charles Witcher.
Anesthesia Progress will continue to provide newer information for our readership about this important problem, since it affects approximately 30,000 dental offices in this country and an estimated 100,000 people at risk. Nitrous oxide has been too valuable an agent for patient care in dentistry and anesthesiology to be hastily condemned. Yet it would be equally unwise to ignore important warnings and risk the heavy hand of rigid governmental controL N. T.
6
ANESTHES1A PROGRESS
THICKENING VAPORS Nitrous oxide may soon be joining the ranks of the unemployed. An article by Allen, in this issue of our JournaL summarizes some of the attempts to control the levels of nitrous oxide pollution found in dental operatories. Based on a survey of anesthetic health hazards among dentists1 using hospital dental operating rooms, it was found that there was a significant increase in spontaneous abortions (78%) in the spouses of exposed dentists. Congenital abnormality rates appeared to be slightly higher (15%) in this same exposed group. The rate of cancer in the exposed group was also higher (35%). Because of the small sample size, these latter two determinations were not statistically significant. The incidence of liver disease was found to be increased 156% in the exposed group compared with the unexposed control. This difference was highly significant. Of course, this operating room study could not isolate nitrous oxide as the likely offending agent, hence other studies of dental operatories where nitrous oxide is the only inhalational agent were advised. Dr. Edward Driscoll Chief, Anesthesiology Section of the National Institute of Dental Research, serving as a pro tem chairman of a special committee of the American Society of Oral Surgeons, the American Dental Association and the American Dental Society of Anesthesiology, convened a meeting in Washington to plan further study of this proW lem. Members in attendance included, among others, Mr. Philip Bierbaum, a representative of the National Institute of Occupational Safety and Health (NIOSH) of H.E.W.; Dr. Charles Witcher of Stanford University's Department of Anesthesiology, where much of the investigational work is being performed.
Published studies by Millard and Corbett2 where concentrations of nitrous oxide
1. Cohen, E. N., Brown, B. W., Bruce, D. L., Cascorbi H. F., Corbett, T. F., Jones, T. W., Witcher, C. E. A survey of anesthetic health hazard among dentists. J Am Dental Assoc. 90:1291-1296, 1975. 2. Millard, R. I., Corbett, T. H. Nitrous oxide concentrations in the dental operatory. J Oral Surg 32:593-594, 1974.
3. Witcher, C., Piziali, R., Sher, R., Moffat, R. J. Development and evaluation of methods for the elimination of waste anesthetic gases and vapors in hospitals. U.S. Dept. of Heath, Education and Welfare, National Insfitute of Occupational Safety and Health Division of Field Studies and Clinical Investigations, Cincinnati, Ohio. May 1975.
JANUARY-FEBRUARY, 1976
5
found in the dental operatory during conscious sedation exceeded hospital operating room levels were cited. Newer unpublished data showing as much as 5000 parts per million (ppm) of N20 in the unprotected dental operatory were presented. NIOSH published a report by Witcher et al. entitled "Development and Evaluation of Methods For the Elimination of Waste Anesthetic Gases and Vapors in Hospitals"3 recommending a maxmum "safe" concentration of only 30 ppm. With the aid of specific modifications of equipment and facilities, it has been possible to reduce dental operatory nitrous oxide concentration to these "safer" levels. Much of this work was carried on by Stanford researchers in cooperation with Dr. Donald Zimmerman. Some of the measures recommended to achieve lowered levels of pollution in the dental office are rather simple: They require scavenging waste gases, equipment maintenance to reduce gas leakage, lower flow rates for sedation and anesthesia cases, improved circulation of room air to prevent build-up of waste gases around the heads of the patient and professional personnel and the incorporation of a new double system inhalation-evacuation nasal mask. Periodic air monitoring is also advised.
"Dentists considering the purchase of scavenging equipment are urged to insist on appropriate documentation that the equipment is actually effective in controlling N20 exposure of personnel and not apt to disturb the anesthetic mixture," advises Dr. Charles Witcher.
Anesthesia Progress will continue to provide newer information for our readership about this important problem, since it affects approximately 30,000 dental offices in this country and an estimated 100,000 people at risk. Nitrous oxide has been too valuable an agent for patient care in dentistry and anesthesiology to be hastily condemned. Yet it would be equally unwise to ignore important warnings and risk the heavy hand of rigid governmental controL N. T.
6
ANESTHES1A PROGRESS
