The purpose of this presentation is to assess the risks to the long-term health of compressed-air divers and to review the actions required to enhance the protection of their health. The scope of this presentation is wide and I will begin by outlining the structure on which this review is based so that the individual pieces of information can be related to the whole. I will omit much of the physiological aspects but can discuss details afterwards.
First the hazards, whether known or merely alleged, to the long-term health of divers will be reviewed.
The methods of surveillance will be described and the question posed as to whether the fact that some apparant abnormality may be found by special investigation necessarily means that the individual's health is compromised. What assessments of long-term health are valid?
Finally the means necessary to identify, assess and control the risks to diver health will be reviewed in relation to there sources that this would require.
The diver must recognize
that he is in an employment that always has been and will continue to be hazardous to his health;
that with good diving procedures these hazards can be minimised;
that with further research, as explained by the previous speakers, and further expenditure for more work, the risks can be control led to a level considered by society to be acceptable.
Since the headline "Divers forced to take lethal short cuts" In the Sunday Times of April 1985, we have all been aware that the factor most likely to influence the future of air diving is the allegation of long-term damage to the central nervous system. But it is necessary to define the wider scope of this review which is to include not only bone necrosis and neurological damage but also mention the known changes in divers of hearing acuity and lung-function, together with the changes to chromosomes These different effects probably have different causes - the majority are not fully understood. There are two ways of looking at the causes - there is the investigation of what is happening within the body at tissue level and the other is epidemiological which is to look at the prevalence of the disease in relation to the relevant history of a large sample group within the population. Both are important, but neither is easy.
The range of physical factors in diving that are potentially hazardous to the long-term health of divers is wide. There is a danger, because the focus of attention today is decompression safety, that other important factors tend to get forgotten. It has been alleged that compression to depth could be such a hazard but although events noticed in the electro-encephalograph (EEG) of deep divers and associated with the high pressure neurological syndrome (HPNS), there is no evidence that persistent EEG changes recorded after a dive are due to HPNS. However this example does illustrate the first problem that we need to acknowledge.
