Dermal exposure to arsenic and lead at a base metals refinery

Abstract

Background: South Africa is the world’s most prominent supplier of platinum group metals. The refining of platinum group metals consists of three main processes namely: smelting, base metal refining and precious metals refining. Dermal exposure to both arsenic and lead has been found to occur during the smelting process of precious metals (Gorman Ng et al., 2017). It is therefore anticipated that exposure to arsenic and lead could also possibly occur during base metals refining (BMR). Objectives: To quantify and compare the dermal exposure of refinery workers to arsenic and lead in the various sampling areas with each other, to compare the exposure on the various anatomical areas with each other and to quantify arsenic and lead workplace surface contamination in order to identify potential sources of exposure. Method: Wipe samples (GhostwipesTM) were collected from the palm, wrist and forehead of workers at various times during the working shift, in one administrative and two production areas within the refinery. In the administration area two workers gave consent to participate in this study. In each of the production areas, six workers gave their consent to participate in this study. Ten wipe samples were collected from each worker per day in the administrative area, only eight wipe samples were collected per worker per day in production area A and B. Additionally, surface wipes were collected to identify potential sources of contamination. A total of 132 wipe samples (112 dermal, 14 surface, 3 media blank and 3 field blanks) were collected during sampling. The collected samples were analysed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) by a South African National Accreditation System accredited laboratory for arsenic and lead. Results: The analytical method used had a detection limit of 1 µg for arsenic and lead. None of the wipe samples contained arsenic at a detectable concentration. Additionally, 14% of the collected wipe samples contained lead at a detectable concentration. The palm received the highest exposure concentration (0.318 µg/cm²) followed by the wrist and lastly by the forehead. Nine of the wipe samples collected from the palm of workers contained lead above the detection limit. Only one of the wrist and forehead wipes collected contained lead above the detection limit. Workers in production area A received higher lead exposure than those in production area B. Surface wipes collected in the administrative area, dirty change house and from the personal protective equipment used by the workers, was contaminated with lead. Conclusion: During the refining process of base metals, workers were not exposed to an arsenic concentration above 1 µg and only six of the workers experienced lead exposure above 1µg. The palm of workers received the highest exposure to lead in both the production areas, which suggests that the palm is the primary area of exposure for the refinery workers. Surface and skin wipe samples indicated that surfaces can act as a source of additional exposure to lead. The control measures already implemented by the refinery prevents workers direct contact with these hazardous substances, which reduces workers’ dermal exposure.