A comprehensive review on the sources, environmental behavior, and degradation of alkylphenol ethoxylates and their metabolites in surface water and soils.

Alkylphenol ethoxylates (APEOs) and their metabolites, widely used in agricultural, industrial, and household products, are known endocrine disruptors. Since the 1980s, many countries have implemented restrictions on their production and use, necessitating an evaluation of these regulations by reviewing their source and environmental behavior in surface water and soils, along with their abiotic and biotic degradation. APEOs and their metabolites have been detected in natural water bodies ranging from ng/L to µg/L, primarily originating from stormwater runoff, wastewater effluent, and sewage sludge. Their lower oligomers (ethylene oxide < 5) are highly lipophilic, leading to significant accumulation in solid phases, particularly in organic-rich sludge/sediments. Their decreasing trend has been reported in fresh surface water, sediments, and sewage sludge, highlighting the effectiveness of regulatory policies. APEOs and their metabolites undergo degradation through abiotic (e.g., UV, H₂/O₂, and photocatalyst) or biotic (e.g., bacteria strains, white rot fungi, and algae) processes, with biotic degradation generally being more cost-effective and efficient. Aromatic ring cleavage is a key pathway for their mineralization and estrogenic toxicity reduction, which predominantly occurs under aerobic conditions and is rarely under anaerobic conditions. Further research should focus on improving immobilized-microorganism processes by exploring cost-effective and efficient microbial immobilization materials to improve APEO mineralization, especially under aerobic conditions.