Comparison of South African short-term and ceiling

Abstract

Occupational exposure limits (OELs) are established with the purpose of regulating exposure to hazardous chemical substance (HCSs) in the workplace. However, the effectiveness of controlling such risks is largely dependent on scientifically up-to-date OELs. For many HCSs, peak levels that go transiently above the time-weighted average (TWA) are acceptable under condition that the exposure is truly for a short period of time. These concentration levels of short-term exposure limits (STELs), are defined as the maximum average concentration to which workers can be exposed for usually a short period of 15 minutes. A limit set for an even shorter period of time are the ceiling limits (CLs), which are intended to protect against high exposures resulting in acute effects. In South Africa, there are two national departments governing occupational health and safety (OHS). The Department of Labour governs the publishing of two types of OELs including STELs, listed in the Regulations for Hazardous Chemical Substance (RHCS). The Department of Mineral Resources (DMR) publishes three types of OELs including STELs and CLs – published in the Mine Health and Safety Regulation (MHSR), the latter OEL exclusively listed by the DMR. Since the original publishing of the STEL and CLs listed in the RHCS (1993) and MHSR (1996) only a few known amendments have been made to the Regulations. This then deems South African STELs and CLs in the Regulations as out-dated. However, as stated earlier, the effectiveness of any type of OEL in controlling risk is largely dependent on scientifically up-to-date OELs. Therefore, the aim of this study was to determine the extent of effectiveness of South African STELs and CLs. This was achieved by comparing the South African STELs and CLs with those of a total of 12 developed countries/organisations based on coverage (frequency and selection) and level (concentration). These 12 countries / organisations included, Australia, Canada (British Columbia), European Union, Finland, Germany, Japan (CLs only), New Zealand, Sweden, United Kingdom and United States of America [NIOSH, OSHA (CLs only) and ACGIH]. Results indicated that there is significant disparity of STEL coverage between the RHCS and the ten selected developed countries/organisations, but in contrast significant similarities in CL coverage between the MHSR and the nine selected developed countries/organisations were observed. Regarding STEL coverage, the disparity was observed from the >5 countries/organisations that had a <50% overlap in HCSs, for both the RHCS and MHSR. Regarding CL coverage there were five developed countries/organisations that had a >50% overlap in HCSs with those of the MHSR. Concerning overall level comparison, there are significant disparities in STEL levels between the RHCS and MHSR, and the selected developed countries/organisations. There are also in contrast significant similarities in CL levels between the MHSR and the developed countries/organisations. The overall level comparison was analysed via the use of the geometric means (GMs) method and interval method. For STEL levels based on the GMs methods, nine and eight countries/organisations had more stringent STEL levels compared to those of the RHCS and MHSR respectively. The interval method results of STEL overall level supports the GMs method which also proved that there were disparities between South African STEL levels and those of developed countries / organisations, with the overall STEL levels of the developed countries/organisations being lower. While conclusions on the overall CL levels were contradictory between the GMs and interval methods, a conclusion was made that there are significant similarities between the MHSR and the developed countries/organisations. This conclusion was based on judgement from the thorough observation of the raw data and based on the literature which stated the lack of variation for most acute OELs over time. Therefore, in conclusion, as concluded by Viljoen (2012) in a previous study comparing TWAs coverage and level, South African STELs are inadequate to regulate acute exposure from HCSs and thereby inadequate to minimising the potential risks of adverse health effects manifesting following short-term acute exposure to HCSs in the workplace. In contrast there are significant similarities in both coverage and level of CLs between South Africa and the selected developed countries/organisations. It may be concluded that South African CLs are adequate enough to regulate acute exposure from HCSs thereby minimising the potential risks of adverse health effects manifesting following very short-term exposure to HCSs in the workplace.