A comprehensive review of toxicity of coal fly ash and its leachate in the ecosystem

Coal fly ash (CFA), a byproduct of coal combustion, is a hazardous industrial solid waste. Its excessive global production, coupled with improper disposal practices, insufficient utilization and limited awareness of its inherent hazards, poses a significant threat to both ecological environment and human health. Based on the physicochemical properties of CFA and its leachates, we elucidate the forms of CFA and potential pathways for its entry into the human body, as well as the leaching behavior, maximum tolerance and biological half-life of toxic elements present in CFA. Furthermore, we provide an overview of current strategies and methods for mitigating the leaching of these harmful elements from CFA. Moreover, we systemically summarize toxic effect of CFA on organisms across various tiers of complexity, analyze epidemiological findings concerning the human health implications resulting from CFA exposure, and delve into the biotoxicological mechanisms of CFA and its leachates at cellular and molecular levels. This review aims to enhance understanding of the potential toxicity of CFA, thereby promoting increased public awareness regarding the disposal and management of this industrial waste.