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Nitrous nightmares?

Dec. 1, 2009
Hygienists compare notes on N2O, pregnancy
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Hygienists compare notes on N2O, pregnancy

by Debra Grant, RDH, CA, and Candice Haas, RDH, BS

The intention of this article is not to promote fear or hysteria, but rather to remind us that we are in charge of our own bodies and lives. We cannot assume that employers will look out for the best interest of their employees. That is not reality.It is up to each person to be aware of proper safety factors. Environment, technology, equipment, and people are some of the things we need to continuously evaluate for toxicity in our lives. That said, here is a true story of events that could be common in your dental office. The following conversation representing six hygienists took place in a public forum.

After the six hygienists' comments, I describe phone calls I made and conversations I had regarding nitrous oxide use in dental offices today. There is also a listing of nitrous oxide manufacturers and distributors.

Hygienist No. 1

"After losing four children (three pregnancies) in the last year, I discovered that the office I worked in during all three pregnancies did not have a properly operating scavenging system. They had the systems serviced after my third miscarriage and the technician found that the scavenging hoses in two of the operatories were completely clogged with dirt. It was so compacted that absolutely no airflow was possible, so it was like having no scavenger system at all. The system was installed 6½ years earlier and had never been serviced; we were unsure of how long the hoses had been clogged.

"Perhaps in an office where N2O was used only once a week for 30 minutes, this might not have been a problem for a pregnant woman. Unfortunately, the dentist I worked for used N2O about five hours a day at 50% concentration on each patient, no matter what his or her tolerance level. In other words, little, if any, titration was taking place. After my third miscarriage and after the system was repaired, the nitrous was monitored in the building by way of a monitoring badge. The reading came back at 62.4 ppm, well above the National Institute of Occupational Safety and Health (NIOSH, the research arm of OSHA) recommended exposure level of <25 ppm.

"The office I worked in also did not have flowmeters to judge the proper flow of the scavenging vacuum.The only training we received on operating this system was, ‘If you can hear the vacuum, the scavenger is on too high.' Of course, now I know this is not true.The scavenger should always flow at 45 liters per minute (lpm).NIOSH states that anything less than 40 lpm will cause significant N2O leakage around the mask. Flowmeters are a must, otherwise the operator has no way of knowing he or she is safe. Dr. James McGlothlin, a NIOSH key researcher, suggested using the Visi–Float™ by Dwyer, as they are the most accurate flowmeters he has found.Without a scavenger flowing at the proper rate, it has been proven that personnel chronically exposed to N2O are at serious risk for adverse health effects, including reduced fertility, spontaneous abortion, birth defects, and renal, liver, and neurological disease.5

"I have since received genetic testing on my last child. It was a girl. Her diagnosis was Turner syndrome, which means there was a loss of the X chromosome. NIOSH has published a Registry of Toxic Effects on N2O, and one of the effects turned out to be ‘sex chromosome loss and nondisjunction.' The geneticist I spoke with said that he usually does genetic testing on each parent after three miscarriages, but after evaluating my baby girl's genes, he did not see the need for further testing. His opinion was, ‘There doesn't seem to be a problem coming from either parent.'

"There have been many studies done on the adverse health effects of chronic exposure to N2O, and I'm blown away at the lack of knowledge there is among dental professionals. Although trivial in comparison to our emotional trauma, my husband and I have paid over $14,000 in medical bills due to our losses.In addition, I am currently unemployed, by choice, because I don't feel that any office is being diligent about having their nitrous/scavenging systems serviced, which includes checking for clogs or leaks.I've only been filling in for other dental hygienists when I'm certain I'm not pregnant.

"I'm curious if anyone else has had multiple miscarriages while employed in a dental office. If you are planning to become pregnant or are currently pregnant, please do not administer nitrous oxide, even if your system is up–to–date. Dr. McGlothlin said that when a patient is receiving 50% N2O, they are actually receiving 500,000 parts of nitrous, and that even with an ideal system there will be some leakage around the mask and from the patient's mouth. Trust me, it's not worth risking. I would encourage everyone (pregnant or not) to have the air quality tested for nitrous oxide in their offices, just to know for sure everyone is safe from its effects. You can order monitoring badges from your dental supplier. It is inexpensive and totally worth knowing that your health is not in jeopardy.

"I hope and pray that no one has had to go through what I have, but hope that I can make a difference in your lives through this experience."
Oklahoma RDH

Hygienist No. 2

"I need to mention my experience with nitrous. I worked at an office in Florida.The scavenger system was dry rotted and taped up.When it was turned on, we could feel air coming out from the tape that was drying up. Whenever nitrous was used on a patient I was seeing, I would get sick to my stomach, start getting a migraine, and feel very dizzy.I complained about the scavenger system and refused to see any more patients that needed the nitrous.

"The dentist ended up paying $600 for a scavenger system, and all I heard was complaining about it from him and the office manager.I couldn't care less. I'm not putting my health in danger for anyone else. If an office doesn't put the health of their employees as a priority, can you imagine the priority to a patient?"
Florida RDH

Hygienist No. 3

"I feel compelled to chime in on the nitrous discussion.I do not use nitrous for my patients/clients, even though I'm way past childbearing years. It makes me ill.The only time that I ever had nitrous delivered to me was when I took the certification course.The instructor refused to pass me unless I allowed my lab partner to administer it to me. The only reason I took the course was to be eligible for various state licensures. I have analyzed my situation and concluded that the reason I get sick is because the nitrous escapes from the person's mouth, not that the scavenger system has leaks.The dentists use rubber dams that effectively block leakage from the mouth.I cannot use a rubber dam for the care that I give.My solution:use many of the desensitizing/anesthetizing agents available, verbal anesthesia, etc."
Washington State RDH

Hygienist No. 4

"I began practicing in 1973 in an office where the dentist used nitrous oxide routinely. A few years later, we learned that nitrous oxide could cause miscarriages. What amazed us was that the N2O could cause miscarriages in the women who worked around it and in the wives of the men who worked around it. As soon as that was discovered, presto! All the offices I knew of had scavenging systems. Does anyone else remember this?"
California RDH No. 1

Hygienist No. 5

"Three of us had miscarriages within the last year in my office (we have 12 employees). I have not been in a room with nitrous oxide in use for over a year now, but my room is10 feetfrom the tanks. I'm going to try to order at least one monitoring badge for the office. Iknow we have never had our scavenging system checked.Anybody know how often these systems should be checked?"
Illinois RDH

Hygienist No 6

"My friend sent me your e–mail. We are both out due to N2O exposure. I have been exposed for the past 20 years to a leaking regulator; then somewhere along the way an O–ring in the wall started to leak, and the nitrous leaked as long as the tanks were on, which was all day. Then a leak was also found down in the tank room. My friend and I had many similar symptoms — anxiety, digestive, and neurological. I'm currently recovering from peripheral neuropathy that seems to be healing."
California RDH No. 2

The Route of Perseverance

CGA (Compressed Gas Association) — I called the CGA, and was directed to their Web site. When I asked about regulations for nitrous oxide use in the dental office, the man read straight off the Web site and referred me to G8.1, which discusses standards for nitrous at consumer sites, including protecting patients, personnel, and property from fire. My reply was, "That's protecting us from fire? What about nitrous filling the air in the dental office?" His reply, "We have no regulations for nitrous use in that respect," and he directed me to the FDA.

FDA (Food and Drug Administration) — The FDA left a message on my phone that said, "The FDA doesn't actually have any regulations for the use of nitrous oxide in dental offices. You'll have to contact your State Board of Dentistry."

ADA (American Dental Association) — The ADA directed me to their Web site for articles concerning N2O, which I had already researched. They said, "If you don't find what you're looking for on the Web site, your state association should know the regulations for your state."

I made a second call to the ADA and spoke with another person. She explained that I must be a member of the ADA to access information from the science division concerning nitrous oxide regulation. I explained that I am a dental hygienist doing some research of my own to find out about the safety regulations. She said I needed to either get my dentist's ADA number or have him call for the information. She directed me to ADSA (American Dental Society of Anesthesiology).

ODA (Oklahoma Dental Association) — Like the FDA, the ODA said that there was no information about nitrous oxide regulation in their office, and that the State Board can give me "absolute regulations."

Oklahoma State Board — A statement from the executive director of the Oklahoma Board from October 20, 2008: "It should be noted, neither the State Dental Act nor the rules and regulations of the board require a nitrous oxide scavenging system to be in use during the administration of nitrous oxide in the dental office."

OSHA (Occupational Safety/Health Administration)— OSHA does not currently regulate nitrous oxide. Nitrous oxide is an asphyxiant at high concentrations. At lower concentrations, exposure causes central nervous system, cardiovascular, hepatic, hematopoietic, and reproductive effects in humans. [Hathaway et al. 1991]

ADSA (American Dental Society for Anesthesiologists) — The spokesperson said, "I don't know if there are federal regulations concerning nitrous oxide use." Again, they referred me to the state dental board for state regulations. In addition, she gave me the number for Dr. Stevens (dentist/educator) in Oklahoma City, who she said should know the answer because he teaches classes concerning conscious sedation in the dental office.

In addition, she gave me the number of a dentist who teaches dental offices for anesthesia permits, which is different than just administering N2O. But the dentist said that when he inspects an office he has a checklist, and "scavenging unit" is one of the items on the checklist. He said he is not aware of any federal regulations.

Nitrous Manufacturers

I then contacted representatives for five nitrous manufacturers. Their responses included:

  • "We just supply the product. We don't have information on chronic exposure to the dental or medical professional." He then read me his MSDS.
  • "NIOSH recommends 25 ppm." When I asked where he got that information, he said, "OSHA." He had looked up the OSHA Web site as we were talking and read it to me. When asked if that information is sent out with the product, he said no, there is no instruction like that sent out with the product.
  • This company suggested that I go to their Web site ( and look up the MSDS. They "don't send that info with the product, but each place (company) should have the MSDS on file," he said.
  • "We don't have information here on exposure levels. Try calling ..." The MSDS specifically says, "There are no known significant effects or critical hazards" under reproduction toxicity, and it does not state what your exposure level should be or that you should not administer while pregnant.
  • "We're not sure of warning labels on tanks," but for exposure levels they told me I should go to the company Web site and look up the MSDS. This site states, in bold print, "Pregnant women should avoid any exposure to nitrous oxide."

There have been only a handful of articles written about the effects of nitrous. I asked several random dentists if they had ever heard of any correlation between nitrous oxide and miscarriages. Every one of them had not heard of that, and said that since they have a scavenger system in their office, everything was "all good." Some were aware of no nitrous use during pregnancy for patients. They said there was nothing said or commented on anywhere that would warn the female pregnant employee or employer not to administer nitrous oxide while pregnant.

After doing much research for a solution or practical safety precautions, the best and most concise I found is from the University of Washington School of Dentistry. Most of the rest of this article is their information ( key highlights are:

"Since it is a gas, its asphyxiating ability must be kept continually in mind as well as its toxic properties; it should not be used with pregnant women."

"Ensure that a properly operating scavenging system is used when nitrous oxide anesthesia is used that includes properly fitting facemasks, and an attendant exhaust system. Room ventilation should be four to 12 room air changes per hour, and the room should be at negative pressure with respect to adjacent rooms. Nitrous oxide containers must be specifically labeled. A medical surveillance program must be in place for operators of nitrous oxide administration equipment, and special training must be available for all operators."

"[dental school employees] are not exposed to concentrations of nitrous oxide (N2O) that exceed the recommendations of the National Institute of Occupational Safety and Health and the Joint Commission for Accreditation of Hospitals. The [latter] suggests maintaining time–weighted average exposures of 25 ppm or less, and NIOSH has recommended, in a proposed standard, that no workers be exposed to time–weighted average concentrations greater than 25 ppm in hospital operating rooms and 50 ppm in dental operatories. These limits were recommended because they are achievable with available technology, not because they assure occupational safety. It is not possible at present to designate a "known" safe level of exposure."

"Nitrous oxide enters the body by inhalation and is readily absorbed through the lungs and transported throughout the body. Short–term or acute exposure to N2O may cause headaches, nausea, fatigue, and irritability. Long–term or chronic exposure is suspected of causing serious health problems including increased incidence of spontaneous abortions and congenital abnormalities, and liver, kidney, and nerve disorders such as peripheral neuropathy."

The occupational safety officers for the dental school also implement control measures, which include:

  • Limit/modify the use of nitrous oxide. Minor modifications in an anesthetist's work practices can substantially reduce anesthetic exposure.
  • Use a specially–designed scavenging system.
  • Use an adjustable, well–fitting nose mask.
  • Minimize speech by the patient during dental procedures.
  • Perform frequent leak testing of equipment.
  • Use fresh air dilution in controlled general ventilation whenever possible.
  • Add an air sweep fan (to dilute gas concentrations).

Where do we go from here?

The part that saddens me is that there are no federal regulations regarding anesthetic waste. What does it take to make this happen? How many more miscarriages must there be?My opinion is that, sadly, there will have to be more tragedies among employers in order for change to happen. With the increasing number of female dentists, the tragedies will be recognized and one day there will be regulation.



About the Author

Debra Grant, RDH, CA, is owner of Oraspa, Inc. Debra is a national speaker on various subjects dealing with complementary and alternative dentistry and dental hygiene. She also serves on the Illinois State Dental Board. You may reach Debra at [email protected] or

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