Assessment of Waste Anesthetic Gas in a Veterinary Clinic

1721 

Professional Poster 

E Lee¹

¹NIOSH, N/A

Eun Gyung (Emily) Lee  
NIOSH

NIOSH conducted a Health Hazard Evaluation to investigate occupational exposure to sevoflurane and health symptoms related to waste anesthetic gases among veterinary healthcare workers during anesthetic procedures. Although time-weighted personal and area concentration levels were below established occupational exposure limits, employee interviews and real-time task-based monitoring revealed episodic peak concentrations during specific activities, indicating the need for control measures to reduce worker exposure.

Waste anesthetic gases (WAGs) are anesthetic gases and vapors that are released into the environment during the administration of anesthesia to patients. Inhalation exposure to WAGs is known to cause adverse health effects, including nausea, dizziness, headache, difficulties with judgment and coordination, DNA damage, genotoxicity, and increased oxidative stress. Furthermore, there are reports of inconsistent findings regarding adverse reproductive outcomes. While scavenging systems are commonly used to capture WAGs, their use is typically limited to operating rooms and often does not extend to recovery areas. In veterinary settings, the use of scavenging systems is even less common than in human healthcare facilities. Furthermore, there is a lack of representative exposure data for veterinary healthcare workers, highlighting the need for systematic exposure assessment to determine appropriate control measures.

"During a two-day field survey at a veterinary clinic, each employee wore two sampling devices: a passive badge (PN 574A, Assay Technology, Inc.) to measure full-shift sevoflurane exposure and a sorbent tube (Anasorb 747, SKC Inc.) connected to a sampling pump, with the tube replaced every hour to assess task-based exposure. Full-shift area air monitoring for sevoflurane was conducted using passive badges at multiple locations within the clinic including the pharmacy, kennels/recovery area, dental cleaning tables, and surgical suite. The pharmacy area was separated by a door from the main treatment area, while the other areas were located in a shared open space. Although the surgery suite had a door separating it from the rest of the clinic, it remained open during both days of the field survey. Sorbent tubes and passive badges were analyzed according to OSHA method 103, with slight modifications made for the passive badges. The limit of detection was 0.9 micrograms (µg) for the sorbent tubes and 0.8 µg for the passive badges. Additionally, real-time area air concentrations were measured every 60 seconds using a portable Fourier Transform Infrared Spectroscopy (DX4040 XL, Gasmet Technologies Inc.; measurable range from 3 parts per billion to 100 parts per million (ppm)) at various locations while employees cared for patients.

At the clinic, all anesthetic procedures were conducted with the use of an active scavenger system. This system minimizes WAG exposure by actively removing gases and vapors by exhausting them through a vacuum system during procedures. A connector for the active scavenger system was located at each dental table in the treatment room and one near the surgery table in the surgery suite.

During the field survey, we also conducted interviews with clinic employees using a questionnaire to gather information on demographics, occupational group (veterinarian, veterinary technician, veterinary assistant, or practice manager), work history, anesthesia-related responsibilities, personal protective equipment (PPE) usage, and health status.

The task-based personal air concentrations were compared to the NIOSH recommended exposure limit (REL) of 2 ppm. The full-shift air concentrations were evaluated against the American Conference of Governmental and Industrial Hygienists (ACGIH) time-weighted average (TWA) threshold limit value (TLV) of 50 ppm, as well as Scandinavian occupational exposure limits (OELs) of 10 ppm in Finland and Sweden, and 5 ppm in Denmark and Norway. A one-way analysis of variance test was conducted to identify differences in task-based personal exposures among occupational groups. Questionnaire data were summarized based on demographic, occupational, and health characteristics."

"On Day 1 of the field survey, six routine dental procedures were conducted, while Day 2 included four routine dental procedures and eight surgical procedures, which included five ovariohysterectomies and three orchiectomies. Generally, dental procedures lasted between 15 and 35 minutes, while surgeries ranged from 10 to 40 minutes.
For the personal exposure assessment, no full-shift or task-based samples exceeded the corresponding OELs. Among 82 task-based samples, veterinary assistants (0.04 – 0.88 ppm) and veterinarians (0.07 – 0.35 ppm) participating in surgical and dental procedures were exposed to significantly higher concentrations of sevoflurane than veterinary technicians performing miscellaneous tasks (<0.03 – 0.07 ppm). The other occupational groups showed no statistically significant differences based on task. Among 19 full-shift samples, the concentrations ranged from 0.03 ppm to 0.14 ppm on Day 1 and from 0.05 ppm to 0.25 ppm on Day 2. Overall, personal exposure concentrations were higher on Day 2 than on Day 1, likely due to increased number of anesthetic procedures on Day 2. All full-shift area concentrations (N=13) ranging from 0.04 ppm to 0.12 ppm on Day 1 and from 0.07 ppm to 0.17 ppm on Day 2 were below the lowest OEL of 5 ppm.
However, real-time area monitoring highlighted the potential risk of elevated peak exposures associated with specific tasks. On Day 2, notable transient peak concentrations were measured during anesthetic procedures involving a small mammal, with sevoflurane levels measured in real-time close to the assistant's breathing zone. The peak concentrations frequently exceeded the instrument's limit of 100 ppm. Although these brief peak exposures might be masked by lower daily average levels, their occurrence indicates that task-specific peaks could have a considerable effect on both full-shift and short-term exposure levels for veterinary healthcare professionals.
We interviewed 13 out of 15 employees (87%) who worked at the clinic during the two-day field survey, with a median workweek of 37 hours and median tenure of 1.2 years. Most interviewed employees reported regularly engaging in tasks that involve handling anesthetic gases. The interviews revealed gaps in training and PPE usage that could further increase exposure risk. Additionally, mild and nonspecific symptoms including headaches, drowsiness, and eye irritation were reported among participants.
In conclusion, while the TWA personal and area concentration levels were below OELs, episodic peak concentrations during specific tasks may still present potential health risks. The findings from this assessment, along with the interview results, indicate the need for effective control measures, such as consistent use of scavenger systems and the implementation of engineering and administrative controls to reduce healthcare workers' exposure to waste anesthetic gases in veterinary settings."

Exposure Assessment