Anaesthetic pollution. Potential sources, their identification and control.

Anaesthetic gases escape into the ambient air mainly from the anaesthetic breathing system but there are many other important sources of anaesthetic pollution. These include the filling of vaporisers, inhalational induction techniques, leaks around the patient's face mask, leaks from monitoring equipment and loose-fitting or perishing equipment. The control of substances hazardous to health (COSHH) regulations together with the recent implementation of the occupational exposure standards (OES) for anaesthetic gases require that any risk to health workers from anaesthetic exposure be assessed, control measures implemented, the environment monitored and OES not exceeded. The installation of costly scavenging equipment is believed to have reduced the levels of pollution in operating theatres, but several independent reports suggest that their use has not been wholly effective. Many sources of pollution remote from scavenging equipment may be responsible for the ineffective control of anaesthetic pollution. During an initial COSHH assessment in our hospital, using an infra-red analyser specifically designed for leak testing and background monitoring, we have identified several controllable sources of pollution. These included leaks from an ill-fitting face mask, loose connections in the anaesthetic breathing system, leaks from the laryngeal mask at the end of the operation and a leak of more than 5400 ppm N2O was found near the unscavenged gas outlet at the back of the multigas monitor. Leak testing, using infra-red analysers with their rapid response, has been recommended as an important aid in the identification of hidden sources of pollution, most of which we believe are amenable to control and remedy.