Ten-year surveys on exposure to waste anaesthetic gases in a large hospital by personal, environmental, and biological monitoring

Introduction
Nitrous oxide, sevoflurane, and desflurane are hazardous chemicals used in surgery and dentistry to anaesthetise or sedate patients. During the use, they can be dispersed into the environment, causing exposure of healthcare workers. This study summarises 10 yrs of surveys in a large hospital in Milan, Italy.

Materials and methods
Annual surveys were conducted from 2015 to 2024. Real-time monitoring and personal monitoring of exposure were performed. Biological monitoring was assessed by urinary nitrous oxide, desflurane, and hexafluoroisopropanol (metabolite of sevoflurane).

Results
101 surveys were performed in 25 operating theatres and 5 dentistry rooms, observing 219 interventions; 383 workers were investigated with 600 paired personal and biological measurements. Sevoflurane was the most used gas (49% alone, 5% with nitrous oxide), followed by nitrous oxide (7%) and desflurane (3% alone, 2% with nitrous oxide); no gas was used in 32% of cases. Median personal exposure for sevoflurane, nitrous oxide, and desflurane was <0.1, 1.4, and <0.1 ppm, with a 95th percentile of 1.2 ppm for sevoflurane in the anaesthesiologist and 428 ppm for nitrous oxide in the dentist. Median urinary hexafluoroisopropanol, nitrous oxide, and desflurane were <0.02 mg/L, <2 µg/L, and <0.3 µg/L, respectively. Real-time monitoring showed peaks of sevoflurane and desflurane during the refill of the vaporiser, the use of a facial mask for the induction, and the tracheal extubation; nitrous oxide peaks were observed during sedation in dentistry. Exposures were higher in paediatric than in adult surgery.

Conclusion
Exposure to sevoflurane and desflurane in general anaesthesia is low; exposure to nitrous oxide in dentistry during sedation may overcome occupational limit values.