Last year the British government launched a new long term strategy for occupational health in an initiative entitled “Revitalising health and safety”.1 Among other things, this set a target of a 20% reduction in the incidence of work related ill health to be achieved by the year 2010. In general, it is good practice to identify criteria against which the success of such initiatives will be assessed, provided that they reliably reflect policy intentions and can be measured satisfactorily. A goal of reducing occupational illness and injury is clearly desirable and easy to sell to the public. On closer examination, however, the target is not straightforward.

For a start, it is unclear what exactly is meant by “the incidence of work related ill health”. One interpretation might be “the incidence of all disorders that could have been caused or made worse by work”. As an example, with this definition, all cases of lung cancer in coke oven workers would be classed as work related as the disease is known to be a hazard of that occupation. Such an approach would be unsatisfactory, however, because for many disorders occupational factors account for only a small fraction of cases, even in the occupations most at risk. It follows that even the most stringent control measures in the workplace might not be capable of reducing their incidence by as much as 20%.

A better interpretation would be “the excess of illness that is attributable to work”. This has the merit that it directly represents the impact of occupation on health at a population level. Moreover, it encompasses not only injuries and diseases caused by work, but also occupational exacerbation of symptoms and disability in pre-existing disorders—for example, asthmatic attacks precipitated by irritants in the workplace. However, it is not …