Occupational exposure to insoluble Nickel in a primary platinum group metal smelter

Abstract

Introduction: Ruthenium, rhodium, palladium, osmium, iridium and platinum are known as platinum group metals (PGMs) and are, together with gold and silver, regarded as precious metals due to their scarcity. The world’s biggest concentration of PGMs can be found in the Bushveld Complex, South Africa. PGMs are isolated from the ore and the metals concentrated into their pure form through a series of complex steps. Insoluble nickel is considered to be a carcinogenic substance and therefore a hazard to human health. It is a by-product of the processes during mining, smelting and refining of PGMs and therefore released in the workplace where workers are exposed to it. Nickel has been classified as carcinogenic by the International Agency for Research on Cancer (IARC), the American Conference of Governmental and Industrial Hygienists (ACGIH), and South African legislation. The general aim of this study was to determine the occupational exposure level to insoluble nickel at a Primary PGM smelter in the North West Province. Historical exposure monitoring data were used in order to identify associations between gender, age, years of employment and occupation, and the level of exposure. Results were also compared to the current Occupational Exposure Limit (OEL) of 0.5 mg/m3 provided by South African legislation and to a stricter OEL of 0.01 mg/m3 proposed by the Scientific Committee for Occupational Exposure Limits (SCOEL). Methodology: One-hundred-and-fifty-two samples collected from 90 study participants over the period of 2010 and 2011 were available for the study. Due to the failure of five sampling pumps during the measurement period, the five samples were discarded as the flow rate and duration could not be determined. Therefore, only 147 samples were available. Descriptive statistics for categorical and continuous data were conducted. Demographic data of the sample population were analysed in order to determine relationships between categorical variables (gender, occupation) and the level of exposure. Correlations between continuous variables (age, years of employment) and exposure level were also determined. Results were also compared to the current South African OEL and to the SCOEL OEL in order to assess current compliance as well as future compliance should the new OEL be adopted. Results: There was no statistically significant difference among the level of exposure of males and females (z = -1.18; p = 0.24), nor among the four age groups (Chi-square = 6.05; p = 0.11) nor among the four years of employment groups and the level of exposure (Chi-square = 1.25; p = 0.74). The difference between the occupation type and level of exposure was small (Chi-square = 20.99; p = 0.051). Single regression analyses indicated a positive significant correlation between the level of exposure and years of employment for instrumentation technicians only (r = 0.77; p = 0.045). Conclusion: The level of exposure was not dependent on the age, duration of employment of an employee or their gender. It was, however, dependent on their occupation. Currently, the smelter complies with South African legislation, but should the SCOEL OEL be adopted in future, control measures should be improved in order to lower exposure levels.C13/4/173