Monitoring occupational exposure to volatile anaesthetics in the operating theatre: environmental and biological measurements

Concentrations of nitrous oxide (N2O) and isoflurane were measured in environmental and urinary samples from subjects occupationally exposed to volatile anaesthetics in operating theatres in a hospital in northern Italy. The aim was to establish whether: an automatic analyzer (Brüel & Kjaer 1302 spectrometer) can be used for fixed position sampling ("anaesthetist zone" and "surgeon/instrument nurse zone"); periodic monitoring of anaesthetics will reduce exposure; exposure to N2O and isoflurane is within legal limits; exposure differs between anaesthetists and surgeons/instrument nurses. Exposure to anaesthetics was monitored twice at six-month intervals. In the first test time spent in the operating theatre was noted and exposure levels were measured automatically. In the second test levels were monitored with passive personal sampling devices. Environmental concentrations of N2O determined by the spectrometer were correlated to urinary levels. Urinary levels of N2O calculated from the regression line were the same as those obtained with the personal samplers. Environmental and urinary levels of N2O decreased significantly from the first to second test. In the second sampling 70% of subjects had levels of exposure to N2O and isoflurane within prescribed environmental limits (50 ppm for N2O and 0.5 ppm for isoflurane). At the first test anaesthetists had significantly higher levels of exposure to N2O than surgeons/instrument nurses. The survey demonstrated that: fixed position sampling data related to time spent in the operating theatre can be used to gauge individual exposure levels; exposure levels decrease after tests following implementation of preventive measures; monitoring needs to be repeated because exposure levels often exceed legal limits; occupational exposure decreases when pollution in the anaesthetic zone is reduced.