Environmental risk assessment for an informal e-waste recycling site in Lagos State, Nigeria

It has been recognised that the informal E-waste recycling may pose a risk to human health and the environment, this study aims to evaluate the e-waste contamination and the environmental and human health impact of informal e-waste recycling on the exposed population using the risk assessment framework. The distribution of a number of heavy metals in soil from an informal recycling site in the largest market for used and new electronics and electrical equipment in West Africa was investigated. The extent of pollution, potential bioavailability of heavy metals, potential risk due to the recycling activities and impact of external factors such as rainfall were assessed. In recent times, bioaccessibility has emerged as a testing tool used to accurately estimate the risk posed on human health by exposure to environmental contaminants, the oral bioaccessibility and inhalation bioaccessibility was also assessed. The concentrations of all the identified metals in the recycling site were consistently higher than values obtained from the control site, suggesting the impact of the recycling activities on the soil. The order of total metal concentration was Cu > Pb > Zn > Mn > Ni > Sb > Cr > Cd for both the dry and wet season. The total concentration of Cd, Cu, Mn, Ni and Zn where was significantly higher (p≤0.001) in the dry season than in the wet season. The concentrations of Cu (329-7106 mg kg-1), Pb (115-9623 mg kg-1) and Zn (508-8178 mg kg-1) were consistently higher than the international soil guideline values. Using a sequential extraction method, the potential bioavailability of the metals was indicated as Cd > Sb > Zn > Cu > Ni > Pb > Cr, suggesting Cd was the most potentially available. Assessing the risk using the Potential Ecological Risk Index (PERI), Cu was found to contribute the most to the potential ecological risk and Cd the greatest concern due to its high toxic-response factor within the study site and the Risk Assessment Code (RAC) suggested Cd posed the most risk in this site. Furthermore, the oral bioaccessibility test showed that less than 40% of the total concentration of all the identified metals was potentially available for absorption in the gastrointestinal tract. In the inhalation bioaccessiblity, with the exception of Cd, the percentage bioaccessibility of the other metals was less than 35% after 120 hours. The health risk characterization indicated the adverse human health effect through the ingestion pathway and a relative lower probability of risk through the inhalation of pathway. This study established a high level of contamination as a result of the informal recycling activities, underscores the importance of applying speciation and bioaccessibility and bioavailability in risk assessment. Finally, in an attempt to evaluate the risk, the study proposed an integrated risk assessment framework which when tried and tested is aimed to positively influence the risk judgement and ultimately risk management decisions whereby providing valuable insights that would translate to an efficient and sustainable management system at the long run.