Physical processing, dismantling and hydrometallurgical treatment of e-waste: A systematic review of risks to occupational and public health

Abstract

Across the Global South, electrical and electronic waste (e-waste) is recovered using rudimentary and often dangerous methods in informal and unregulated facilities. Although these activities provide a valuable contribution to the global circular economy, their uncontrolled nature results in a risk of potentially hazardous substance emission into the environment from where they may pose considerable risk to both occupational and public health. Here, we focus a systematic PRISMA review on two distinct groups of activities undertaken in e-waste management in low- and middle-income countries (LIMICs): (i) Physical deconstruction and reclamation, involving dismantling assemblies of items and materials to recover value; and, (ii) hydrometallurgical treatment, involving the dissolution and suspension of precious metals using solvents (cyanide) and acids (aqua regia). For comparison purposes, we consolidate information on (i) and (ii) according to the types of substances evidenced; and identify, critically assess and rank most prevalent hazard-pathway-receptor (H-P-R) risk combinations experienced by people working across the Global South. Despite the proliferation of publications, evidence to assess risk is comparatively limited. Still, we are confident to highlight the extremely hazardous nature of work undertaken, often by children, handling highly hazardous substances without protective equipment to reclaim gold and other precious metals using hydrometallurgical processes. Emissions of hazardous substances, particularly potentially toxic elements (PTEs) from physical dismantling also represent a serious risk to health. Numerous sources speculatively link concentrations in the environment (a significant risk to children who have a tendency to eat soil) to e-waste dismantling processed. However, many of the sources that identify elevated substance concentrations in environmental media face difficulties in unambiguously and convincingly linking emissions from specific activities to the environmental concentrations, i.e. establishing causality. This key limitation presents us with a challenge for designing and implementing interventions to target, control and replace such highly risky resource recovery methods. Yet, such insufficient information cannot be used as an excuse for inaction, especially as our generalized H-P-R inferences here provide for sufficient interlinkages.