Scoping Review on Soil Contamination from Lead-Zinc Slag and Environmental Assessment Methods

Lead-zinc slag and smelting activities represent a persistent global source of soil con-tamination, releasing toxic heavy metals — lead (Pb), zinc (Zn), cadmium (Cd), and arsenic (As) — with documented risks to ecosystems and human health. No systematic mapping of environmental assessment methods for slag-contaminated soils exists, and evidence from Central Asia remains entirely absent. This scoping review, following PRISMA-ScR 2018 guidelines, maps the global evidence base on soil contamination from lead-zinc slag and associated assessment methods. Searches across Dimensions, PubMed, and OpenAlex identified 410 records; 56 studies (2010–2025) met inclusion criteria. Studies were concentrated in China (35.7%), Poland (8.9%), and Brazil (7.1%); no studies from Kazakhstan were identified despite major Pb-Zn smelting operations in the Shymkent region. All studies reported heavy metal concentrations exceeding regulatory thresholds, with cadmium as the primary ecological risk driver and lead posing the greatest health risk to children. Assessment methods included pollution in-dices (73.2%), ecological risk assessment (67.9%), GIS-based spatial analysis (57.1%), human health risk frameworks (51.8%), and source apportionment models (50.0%). Post-2018 studies increasingly applied integrated multi-method frameworks. Critical gaps include the absence of Central Asian research, limited predictive modeling, and lack of standardized protocols. Findings provide a structured evidence map to guide environmental monitoring and remediation at slag-contaminated sites globally.