Occupational medicine at a turning point.

W ith the successful control of many of the most serious occupational hazards to health, the focus of occupational medicine in developed countries has shifted to other work related disorders that are rarely fatal but cause substantial disability. This paper hypothesises that many of these disorders do not arise from detectable organic pathology, but rather are a psychologically mediated response to triggering exposures that is conditioned by individual characteristics and cultural circumstances. If correct, this has important implications for the way in which such illness should be managed and prevented. Proposals are made for ways in which the hypothesis could be tested. Occupational medicine first emerged as a specialist discipline in response to chemical, physical, and biological hazards that caused serious and often fatal disease. A framework was developed for the management of such hazards that entailed assessment of the relation between exposure and risk; reduction of exposure (by elimination of the noxious agent, improved engineering, modified systems of work or the use of personal protective equipment); and monitoring to check that controls on exposure were effective. This approach has been notably successful, preventing much avoidable morbidity and mortality. For example, in Britain, occupational diseases such as bladder cancer in the rubber industry (from exposure to 2-naphthylamine) and phossy jaw (caused by exposure to white phosphorus) have now been eliminated. As many of the most serious occupational hazards have been successfully addressed, attention has shifted increasingly to other work related disorders which are rarely fatal, but which nevertheless give rise to widespread illness and disability, and account for substantial loss of time from work and demand for healthcare. Thus, when Harrington and Calvert conducted a survey of managers and occupational physicians in 1996, both professional groups identified musculoskeletal disorders and occupational stress as the two highest priorities for research. This is not surprising, given the enormous cost of these problems to the national economy. For example, in 1993 back pain alone was estimated to account for an annual loss of 52 million working days in Britain, and to cost the National Health Service some £480 million per year. At the same time, the successes of occupational medicine have raised public awareness of the potential dangers of occupational hazards, leading to widespread concern that new technologies such as pesticides, genetically modified crops, and mobile phones, could pose important unrecognised risks to health. These anxieties are reinforced by sensational reporting in the media, and in addition to the demand for research on musculoskeletal disorders and stress, there has been an imperative to focus activity on possible adverse health effects associated with technological innovation. Perhaps not surprisingly, in turning to these new problems, occupational health practitioners have continued to apply the approach to risk management that has served so well in the past. It is assumed that a noxious agent or activity produces an injury that can be prevented by eliminating or reducing exposure. In some cases, the model seems to work well. For example, there is now good evidence that frequent heavy lifting in the workplace is an important cause of degenerative damage to the hip joint, 6 which in Britain has led to the recognition of hip osteoarthritis as a prescribed occupational disease in farmers. However, it is becoming apparent that for many other disorders the traditional paradigm may be less apt. These include ‘‘mechanical’’ low back pain; many neck and arm complaints; illness attributed to low level exposure to organophosphate insecticides; multiple chemical sensitivity; Gulf War illness in military personnel; sick building syndrome; and acute illness associated with the use of mobile phones. All of these disorders are associated with potentially noxious occupational exposures, but various observations suggest that their relation to work is not straightforward. Some of them have exhibited remarkable time trends that cannot be explained by their assumed occupational causes. For example, in Britain, social security statistics indicate that rates of incapacity for work because of back problems increased more than sevenfold between 1953 and 1992, at a time when the physical demands of work were generally reducing. And in Australia there was a major epidemic of disability from arm pain among office workers during the early 1980s that later subsided without any significant change in working methods. Similarly, there is marked geographical variation in their occurrence and in the public concern which they have generated, which cannot readily be explained by differences in industrial practices. Thus, the outbreak of arm pain in Australia during the 1980s was not paralleled in other countries that were using similar technology and working methods; multiple chemical sensitivity has been a more prominent problem in the USA than the UK; ‘‘electrical hypersensitivity’’ has been reported more often from Scandinavia; and chronic disabling illness following low level exposure to organophosphate insecticides seems to be particularly a problem in Britain. A feature which all of the disorders share is that despite much research, there is rarely convincing evidence of underlying pathology. Moreover, in many cases the reported symptoms are remarkably similar even when the alleged causal exposures are very different. Thus, complaints such as fatigue, difficulty with memory, difficulty with concentration, tinnitus, dizziness, and numbness and tingling have been linked with service in the Gulf War, use of mobile phones, and exposure to organophosphates, and general tiredness is also the most common complaint in sick building syndrome. These symptoms all occur in the population at large, but are found more frequently in people who have been exposed to the assumed occupational hazard. The nonspecificity of symptoms and absence of identifiable underlying pathology raise the possibility that psychological factors contribute importantly to the illnesses. In support of this, there is now a strong body of evidence that disorders such as low back pain and non-specific arm pain are consistently associated with, and predicted by, low mood and lack of vitality. This is in apparent distinction to hip osteoarthritis. In a study of patients awaiting hip replacement for osteoarthritis, there was an EDITORIAL 281