Recommendation of a classification system and occupational exposure limits for chemical carcinogens

Abstract

Introduction: An increased number of occupational cancers reported annually can be attributed to workers being exposed to hazardous chemical substances (HCSs) in their workplace. Carcinogen classification systems such as the International Agency for Research on Cancer (IARC), the American Conference of Governmental Industrial Hygienists (ACGIH), Environmental Protection Agency (EPA), National Toxicology Programme (NTP) and the European Union (EU) help to identify the carcinogenic risk associated with certain HCSs with the help of data collected from scientific research programmes. Incorporation of such a system into South African legislation may reduce the number of occupational cancers developed by the South African workforce. Aim and objectives: The Aims and objectives are as follows: (1) to evaluate existing carcinogen classification systems of developed countries in order to establish which system or combination of systems is the best option to use for establishing a carcinogen classification system to be recommended for incorporation into South African occupational health legislation; (2) To identify hazardous chemical substances (HCSs) listed in the carcinogen classification systems of developed countries and to compare them with the HCSs listed in the Regulations for Hazardous Chemical Substances (RHCS) and the Mine Health and Safety Regulations (MHSR) that should be classified as carcinogenic; and (3) to compare the occupational exposure limits (OELs) of above mentioned carcinogens as listed by developed countries or organisations with the OELs listed in the RHCS and the MHSR. Methods: A carcinogen classification system was identified by making use of set criteria points. Thereafter, the HCSs that were considered human carcinogens were identified in the RHCS and the MHSR using the selected carcinogen classification’s notations. The OELs listed in the RHCS and MHSR for these HCSs were then compared to the OELs listed for the same HCS’s OELs within ten developed countries/jurisdictions with the help of the geometric means method. In addition the interval method was used for the comparison of the number of MHSR OELs that are similar, lower or higher than that of the RHCS. Results: The carcinogen classification system with the highest score was the IARC. Therefore, this study used the HCSs classified as human carcinogens by the IARC. The RHCS contains two tables that list OELs for HCSs namely Table I and Table II. The total number of HCSs listed in the RHCS (Table I = 22 HCS and Table II = 55 HCS) was 77. It was found that the country/jurisdiction with the lowest geometric mean when Tables I and II were combined was Finland with a geometric mean of 0.300. It was found that there is no statistical significant difference (p = 0.138) between the geometric means of the RHCS’s Table I and II. The database for the MHSR only contained 76 substances listed as carcinogenic by the IARC. Finland also had the lowest geometric mean with a value of 0.475. Since the geometric mean for Finland in both the analysis for the RHCS and MHSR was far below 1, it indicated that the OELs contained in this list was the lowest of all the developed countries included in this study. When the interval method was used to determine the number of MHSR OELs for carcinogens that are similar, lower or higher than the RHCS OELs it was found that 64.5% of the RHCS OELs are similar to the MHSR and 34.2% of the MHSR OELs were lower than the RHCS OELs. Conclusion: The carcinogen classification reasonably practicable for use within South African occupational health legislation is the IARC’s carcinogen classification, which classified a total of 481 substances of which the RHCS contained 77 substances and the MHSR contained 76 substances classified as carcinogenic to humans (Group 1, Group 2A and Group 2B). It was found that South African OELs are at a higher level than the OELs listed by some developed countries. The geometric mean values calculated for most developed countries were below 1 with the exception of OSHA in the RHCS. In the MHSR it was found that OSHA, Australia and the United Kingdom had a geometric mean >1. When the RHCS’s OELs were compared to the MHSR a geometric mean of 0.651 was calculated that confirmed the overall level at which OELs of the MHSR are set were at a lower level. Using the lowest available OEL from all countries/jurisdictions will provide protection to the workforce in South Africa against the development of occupational cancer.