The Definition of Waste Anesthetic Gases (WAGs)

Definition of Waste Anesthetic Gases (WAGs)

Waste anesthetic gases (WAGs) are small amounts of inhaled anesthetic gases and vapors that escape into the air of the workplace during patient care. They include nitrous oxide and halogenated agents such as sevoflurane, desflurane and isoflurane. Workers can be exposed in operating rooms, post-anesthesia care units, dental offices, veterinary clinics, labor and delivery units and any area where inhaled anesthetics are used or where patients exhale them during recovery.

Leaks can occur from loose connections, poorly fitting masks, uncuffed endotracheal tubes, inadequate scavenging, filling vaporizers, and from patients exhaling residual gas after anesthesia. Veterinary practices can see higher exposures from induction chambers and mask inductions.

Health Effects

Short-term exposure to higher levels can cause headache, fatigue, irritability, nausea, drowsiness and problems with judgment and coordination. Long-term exposure has been studied for possible effects on reproductive health, including miscarriage and reduced fertility, particularly with nitrous oxide. Nitrous oxide also interferes with vitamin B12 function, and heavy exposure can affect the nervous system and blood cells.

Exposure Limits and Guidance

OSHA has no permissible exposure limits for anesthetic gases. It published guidelines for workplace exposures to anesthetic gases that describe how to control them, and it can enforce under the General Duty Clause and its hazard communication and respiratory protection rules.

NIOSH recommends:

• Nitrous oxide: 25 ppm as a time-weighted average during the period of anesthetic administration.
• Halogenated agents: a ceiling of 2 ppm over 60 minutes when used alone, or 0.5 ppm when used with nitrous oxide.

ACGIH publishes threshold limit values for some of these agents, including 50 ppm for nitrous oxide.

Controlling Waste Anesthetic Gases

Engineering controls

• Scavenging systems: collect excess gases from the breathing circuit and vent them outside. They must be connected and working for every case.
• General ventilation: operating rooms and recovery areas should have adequate air exchanges as set by building and healthcare ventilation standards.
• Equipment maintenance: check anesthesia machines, hoses, connectors and vaporizers for leaks on a regular schedule.

Work practices

• Check the anesthesia machine and breathing circuit before each use.
• Do not turn on gas flow until the mask or tube is in place, and turn it off before disconnecting.
• Use well-fitting masks and cuffed tubes where clinically appropriate.
• Fill vaporizers carefully using key-filler systems, ideally with gas flow off.
• Flush the breathing circuit into the scavenging system at the end of a case.
• In veterinary settings, minimize mask and chamber inductions and flush induction chambers into the scavenging system before opening them.

Monitoring and training

Air sampling and leak checks, often coordinated by industrial hygiene staff, help confirm controls are working. Staff should be trained on the hazards, controls and how to report leaks or symptoms under the hazard communication program.

Example of Waste Anesthetic Gases

Recovery room nurses at a surgical center reported frequent headaches late in their shifts. Air sampling showed elevated levels of sevoflurane near patients who had just arrived from surgery, as they exhaled residual gas.

The center increased the air exchange rate in the recovery area, arranged beds so nurses were not working directly in front of patients' faces during early recovery, and reviewed the end-of-case routine in the operating rooms so circuits were flushed into the scavenging system before patients were moved. Follow-up sampling showed lower levels, and reports of headaches dropped.

Frequently Asked Questions: Waste Anesthetic Gases (WAGs)

Does OSHA have a limit for anesthetic gases?

No. OSHA has guidelines but no permissible exposure limits. Employers commonly use NIOSH recommended limits and ACGIH TLVs.

Who is most at risk from waste anesthetic gases?

Anesthesia providers, operating room and recovery staff, dental staff using nitrous oxide and veterinary staff, especially where scavenging is poor.

Are pregnant workers at greater risk?

Some studies have linked exposure to reproductive effects, especially with nitrous oxide in poorly controlled settings. Pregnant workers should discuss their exposure with their employer and healthcare provider.