Barry Mc Mahon is a Senior Physicist working in St James's Hospital, Dublin.

Barry has spent many years in contemplation of the world of Gluteraldehyde.

It is very difficult in a field so specialised and yet diverse as Clinical Engineering to stay within the brief of a job specification without wandering into side issues. However we cannot ignore issues such as Health and Safety, when they arise, especially when they do not fall into any other category. Especially as there may be nobody else in the hospital aware of or responsible for the issue.

The Issue Gluteraldehyde has been around as a cold chemical disinfectant for almost 20 years. Although it has been superseded by many different products during its existence, it has again and again been brought back as the disinfectant of choice by users on the basis that it does a good job, it is not harmful to the products placed into it and it is relatively inexpensive. However it is a respiratory irritant, causing occupational asthma and sensitisation in certain individuals.

So if , for example, we are to specify endoscopic reprocessing equipment it cannot be done in isolation from the health issues it might raise. It is unwise to assume that any of the newer products such as Nu-cidex are safe enough that any of the precautions necessary for using gluteraldehyde based disinfectants can be relaxed.

Once we have specified the system and even after we have bought the system, how can we guarantee that the occupational exposure level as required by NIOSH to be less than 0.2 PPM for the 15 minute reference period ?

This is clearly an example of how technical equipment supporting personnel can inadvertently become involved in an occupational health issue.

If for example you have a ventilation system for containing gluteraldehyde fumes that uses carbon filtration to recycle the air how can you ensure that the filter is effective or how can you decide when it needs to be replaced. Monitoring Levels The obvious solution is to monitor the vapour levels. This may not be as easily carried out as one would imagine. One company sells a meter that supposedly gives a readout of the concentration of gluteraldehyde in the air. However on initial tests we found this meter not to be reproducible and this was later confirmed by publications in the literature. It was even sensitive to other aldehydes such as those found in perfumes and cleaning agents;

After a small amount of research and a little bit of luck we traced a chemical company who could make gluteraldehyde measurements for us.

Two sophisticated methods are used to measure levels both based on the same principle.

A glass tube containing a substance which absorbs the gluteraldehyde vapours is placed in the measurement area and an accurate vacuum pump draws the vapours across the tube. The gluteraldehyde vapours can then be collected later by drawing air over the tube. Then the concentration of gluteraldehyde can be determined by either high pressure liquid or gas chromatography. Recently on tests this method has been proven to be the most accurate available.

The problem is that the method is quite complex and requires the services of companies specialising in it.

However for peace of mind and to allay the worries of user it can be carried out for about $100 per site if you are getting a number of sites done together.

Remembering that you can smell gluteraldehyde at lower levels than what is considered to be dangerous, therefore your nose is not necessarily a good indicator as to the danger level.