Studies which investigate the effectiveness of occupational health interventions to reduce exposure or adverse health outcomes or both are important. They may show us what works and, just as importantly, what does not work, or at least give us pause for thought. Despite their value, these studies, particularly those using a randomised or cross-over design, are relatively rare in occupational medicine. Their scarcity is explained in part by quite substantial impediments to undertaking the research,1–3 ethical considerations not least among them. Withholding an intervention, especially one selected because it is thought to work and to prevent a serious disease, from a control group clearly has ethical implications. Also, they can be expensive, for example if equipment has to be bought and introduced into participating workplaces. Additionally, the impact may take years to be evident, requiring long-term resource allocation and the prospect of years of work before publishable answers on the effectiveness of the intervention are available.

This commentary uses three South African studies to demonstrate the value of well-designed intervention effectiveness research. These examples provide support for the greater use of these studies, despite their difficulties, even in a middle-income country with resource constraints.

The first is a paper by Baatjies et al4 published in this journal which shows that practicable interventions substantially …