The hazards presented by arsenic are well known, and the notoriety gained by its use as a poison in previous years has affected attitudes towards the commercial production and employment of a very useful substance. It is not widely realized that Britain was the world's largest producer of arsenic around the turn of the century. Production has now ceased and any reserves that still exist will probably remain unexploited, despite the modern requirement for arsenic by the wood treatment and microelectronics industries. This demand is being satisfied by mines in other countries which use essentially the same refining process as that employed in England a century ago. This paper compares what is known about conditions of work and health in the English arsenic industry then with modern conditions at a Chilean production plant, and shows how the perception and management of the risks involved in a hazardous operation stems from the complex inter-relationship of technological, social, political and economic factors. In particular, the results of this survey explain why, in many previous surveys, a poor correlation was found between airborne and urinary arsenic measurements. Both measures appear to be strongly influenced by the particular type of work undertaken and this can be related to the chemical form of the arsenic present. Within each job category, the most important factor affecting their correlation is the difference in use of respiratory protection equipment.