Does the science support our practice? : letter to the editor

Recent discussions about the Department of Mineral Resources' (DMR) "Guideline for the compilation of a mandatory code of practice for personal exposure to airborne pollutants', and the associated 'Airborne pollutants-Particulates Personal Exposure Report Form 21.9(2)(a)" (see the report on the Occupational Health Dialogue Workshop by Brian Mongoma and Vijay Nundlall in this issue) have demonstrated that there is an urgent need for a critical review of the scientific rationale for a number of current occupational hygiene practices in the mining industry as prescribed in the above-mentioned Guideline. One such practice is the application of the additive rule for exposure to particulates, as operationalised in the Air Quality Index (AQI) and, more specifically, the role of particles not otherwise classified (PNOCs).