Environmental Toxicity of IBA-Derived Permeable Blocks under Climate Change

Reusing incineration bottom ash (IBA) in permeable blocks offers the potential for sustainable construction and urban stormwater management. This study evaluates the long-term leaching behavior of IBA-derived blocks under future climate conditions in Hong Kong, focusing on temperature projections of up to 35 °C and total precipitation reaching 600 mm annually over the next 15 years. Using the USEtox model, the study modifies the exposure factor to reflect changes in leaching dynamics. The findings show that under high temperatures (35 °C) and high L/S ratios, leaching rates of heavy metals, particularly chromium (Cr), exceed SPLP predictions, especially for blocks with higher IBA substitution ratios. The highest risk is associated with 100% IBA-derived blocks, where Cr mobility increases under warmer and wetter conditions. The study emphasizes the need to incorporate climate change impacts into life cycle assessment (LCA) of waste-derived construction materials. Recommendations include reducing the IBA substitution ratio in hot, humid regions to minimize risks. In contrast, higher IBA ratios may be suitable for cooler, drier areas. Long-term monitoring and risk assessments are critical for managing environmental and health impacts. This research establishes a framework linking climate projections with environmental risk assessment, supporting safer and more sustainable material applications.